Pacific Island Ecosystems at Risk (PIER)


Report on invasive plant species in Palau (2008 survey)


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Introduction

Significant new species found in this survey

Species that are subjects of eradication programs

Major species that are invasive or have the potential to become so in Palau

Other species of concern that are known to be weedy or invasive elsewhere and are common, weedy or cultivated in Palau

Native species (or Micronesian introductions) exhibiting aggressive behavior

Invasive plant species not known to be in Palau

Invasive plants associated with the Compact Road

General observations and recommendations

Species-specific recommendations

Recommendations by State

Appendix 1.  Invasive plant species of Palau

Appendix 2.  Invasive plant species not known to be present in Palau

Appendix 3.  Invasive species present in Hawai‘i, Guam, Yap, Papua New Guinea, Philippine Islands or Taiwan but not present in Palau

Appendix 4.  Invasive species of environmental concern by location

Appendix 5.  Other invasive species by location

Appendix 6.  Presence of invasive species of environmental concern within Palau

Appendix 7.  Presence of other invasive species within Palau

Appendix 8.  Risk assessments for introduced species in Palau

Appendix 9.  Scientific name synonyms

Appendix 10.  Background material and references


 

Report to the Republic of Palau: 2008 update on Invasive Plant Species

 

James C. Space, David H. Lorence and Anne Marie LaRosa

U.S.D.A. Forest Service

Pacific Southwest Research Station

Institute of Pacific Islands Forestry

Hilo, Hawai‘i, USA

2 March 2009

 

 

Report to the Republic of Palau: 2008 update on Invasive Plant Species

James C. Space, David H. Lorence and Anne Marie LaRosa1

In 2002, The Republic of Palau requested assistance from the US Department of Agriculture, Forest Service, Institute of Pacific Islands Forestry, to conduct a survey of invasive plant species of environmental concern. A comprehensive survey of the entire country was conducted and a report of the findings was submitted to the Government of Palau in 20032. This superseded a more cursory survey of the major species of environmental concern conducted in 19983. The present survey was requested as a follow-up to the 2002 survey.

The objectives of this survey were to: (1) identify new invasive plant species that had become established in Palau since the 2002 survey; (2) find species that had been missed in the prior survey; (3) assess the behavior of newly found species as threats to the environmental integrity of Palau; (4) review progress in the management of invasive plant species, particularly in regard to recommendations in the 2003 report; and (5) make appropriate recommendations for consideration by the Government of Palau for management of invasive plant species in the future. As previously, the intent was to conduct an overall survey of the weed flora of the islands. Given the limited duration and nature of the survey it is likely that some potentially invasive species, particularly those occurring in low numbers or cultivated in urban gardens or occurring as agricultural weeds, were still overlooked. Periodic reconnaissance surveys and additional surveys of sensitive areas can and should be conducted as needed.

Joe Tiobech and Dino Mesubed of the Palau Bureau of Agriculture accompanied and assisted us in the field, showing us sites of known and suspected infestations and pointing out previous management activities4. Our primary field references were checklists prepared from the 2002 survey, a checklist of collections made by Dr. Lorence and his colleagues, and a checklist by Kitalong et al. (in press). These checklists also incorporated species previously recorded by others (see Appendix 10, References).

The survey team inspected the islands of Koror, Malakal, Ngerkebesang, Babeldaob, Angaur Peleliu and Kayangel by vehicle, focusing on disturbed sites such as roadsides, airstrips, ports and ‘urban’ areas. Rapid visual inspection and recording of species along the routes chosen was accompanied by more detailed inspection on foot at a variety of sites or when suspected new species were seen. On Babeldaob, particular attention was given to the recently completed Compact Road. The Rock Islands of Bab el Omekang, Bkul a Chesemiich, Ngchelobel, Ngchus, Ngeanges (Neco), Ngercheu (Carp Resort), Ngerchong, Ngeremdiu and Ngemelis were visited by boat and inspected on foot. All but the latter were visited in the 2002 survey; Ngemelis was included in this survey to gather baseline data as it has recently been opened to the public. We were not able to revisit Betikel, Ngidech or Ulong islands due to lack of time. The islands of Sonsorol and Hatohobei States were not surveyed. It would be highly desirable if these islands could also be reassessed in the future.

Herbarium specimens (225) of new, significant, taxonomically difficult or unknown species were collected for later identification or verification. All voucher specimens and duplicates will ultimately be deposited in the herbarium collections of the National Tropical Botanical Garden (PTBG) and the Belau National Museum (BNM) with duplicates to the New York Botanical Garden (NY) and the Smithsonian Institution (US) when available.

For the purposes of this report, invasive species occurring in or of threat to Palau have been grouped into six categories:

  1. Species that have been subjects of eradication programs (7 species, listed in Appendix 1, Table 1).
  2. Major invasive species that are invasive or potentially invasive in Palau and are of significant concern to natural or semi-natural ecosystems (55 species, listed in Appendix 1, Table 2).
  3. Other species of concern that are invasive or weedy elsewhere and are common, weedy or cultivated in Palau (138 species, listed in Appendix 1, Table 3).
  4. Species of low risk or of agricultural concern that are invasive weeds in gardens, fields, and pastures and along roadsides (156 species, listed in Appendix 1, Table 4).
  5. Native species (or Micronesian introductions) that exhibit aggressive behavior (16 species, listed in Appendix 1, Table 5).
  6. Species that are invasive elsewhere in similar ecosystems but were not seen on our visit and are not reported in the literature as being present in Palau, of which 631 species are of known or potential environmental concern (Appendix 2, Table 1) and 276 other invasive species (Appendix 2, Table 2).

These species are listed in the tables of Appendix 1 and Appendix 2 with commentary on the more significant species in the following text. Additional information about each species is located on an Internet site, http://www.hear.org/pier, and on the PIER-CD, copies of which have been made available to the Ministry of Resources and Development, the National Invasive Species Coordinator, Palau Community College, the US Natural Resources Conservation Service, The Nature Conservancy, the Belau National Museum, the Palau Conservation Society and others.

1. Significant new species found in this survey

Widespread

Erigeron bellioides (fleabane daisy) was previously noted by Lorence and Flynn (1998) on Koror. In this survey we found it present on most islands [vouchers 9737, 9763 and 9864]. It may have been present and missed on some islands in the previous survey, but it has obviously spread widely since that time. It is present elsewhere in Micronesia and is a fairly recent introduction to Hawai‘i. It has tiny seeds (achenes) that may be spread by the movement of soil, as a hitchhiker on footwear or on the feet of birds (Nagata, 1995).

Hamelia patens (firebush, redhead, scarletbush) is in cultivation in several yards on Peleliu [voucher 9745] and elsewhere. The flowers are being used for leis. This species is listed as a weedy species by Holm et al. (1977) and has a reputation of being weedy in its native range. A weed risk assessment for this species resulted in a score of 7, characterizing it as "high risk".

Sesbania cannabina (prickly sesban) is not new but has become significantly more widespread since the 2002 survey. It was seen along roadsides in Malakal [voucher 9717], near the dump in Koror, and at several sites along the Compact Road on Babeldaob [voucher 9808]. It is a nitrogen-fixing species so it can readily grow on poorer soils. Although it is a woody small shrub or sub-shrub, individuals seem to die back after a short period of time. A risk assessment prepared for Australia gave this species a score of 17, "high risk". It is mentioned as being invasive in Yap (Fosberg & Falanruw, 1980), Guam (Stone, 1970) and New Caledonia (MacKee, 1994). Joel Miles (pers. com.) reports that the Compact Road construction apparently contributed to its spread—it appeared in several areas where soil was added when the road was almost complete. The source of the soil could not be determined. Vehicle traffic may be aiding its further spread along roads.

Babeldaob

Aeschynomene americana (American joint vetch) [vouchers 9812 and 9915] was collected on the Compact Road near the airport. This weedy species had previously been reported by Fosberg et al. (1979) and there are voucher specimens in the Belau National Museum. This species has a risk assessment score of 12 and is rated "high risk".

Alternanthera ficoidea [=A. tenella] ‘Bettzickiana’ (sanguinarea) a small variegated ornamental plant, was seen planted for landscaping at the Capitol [voucher 9845]. It was also seen in cultivation in Koror and Malakal and on Ngerchong Island [voucher 9869]. GRIN (USDA, 2008) lists the species as native to the Caribbean and Central and South America with the notation "naturalized elsewhere". According to Barbara Waterhouse (pers. com.) the species is a minor weed in northern Queensland. Elaisson (1987) says that it is a "common and widespread species in the tropics of the New World and has spread to warm areas in some parts of the Old World". The behavior of this particular cultivar is unknown, but should be monitored.

Alternanthera sessilis (sessile joyweed) was recorded along the Compact Road [vouchers 9821 and 9822a). This species was previously recorded by Fosberg et al. as a native species but was not seen in the 2002 survey.

Alysicarpus bupleurifolius (sweet alys) [voucher 9813] was collected on the Compact Road near the airport. It is not new as it was previously recorded by Fosberg et al. (1979) from both Babeldaob and Malakal, but was not noticed in the 2002 survey. This weed is native to tropical Asia and is reportedly naturalized in Queensland, Australia (USDA, 2008).

Aniseia martinicensis (whitejacket) was found along the Compact Road [voucher 9905]. This species was previously noted by Fosberg et al. (1979). It appears to be a minor weed of roadsides and disturbed areas that has been present on Babeldaob for a long time but was not seen in the 2002 survey.

Brucea javanica (Java brucea, Macassar kerneltree) [voucher 9888] was found along the north extension of the Compact Road. It was previously recorded as a native species by Fosberg et al. and Raulerson et al., but is probably an introduced species per Backer and Bakhuizen van den Brink (1963-1968).

An example of Bryophyllum delagoense [=Kalanchoë tubiflora] (chandelier plant) was seen in cultivation with some reproduction around it. This species can be a problem in dry, rocky disturbed sites. It reproduces by plantlets and bulbils produced on the margins of the leaves. It is naturalized in the Hawaiian Islands and is present, at least in cultivation, on Guam and several other Micronesian islands.

Buchnera americana (American bluehearts) [voucher 9831] was found in grassy areas along the airport runway, in front of airport terminal, and scattered elsewhere in the locality. This species seems to be making its way around the Pacific as it is apparently a recent introduction to Guam and Rota (Raulerson, 2006) and several of the Marshall Islands (Vander Velde; 2003, 2006, 2007) [Note:  This species was found on review to be Buchnera floridana].

Chloris virgata (feather finger grass, feathery Rhodes grass) [voucher 9816], a new record for Palau, was found along the Compact Road near the airport. This species is reported to be an aggressive invader of degraded land in Australia (Smith, 2002) and is "naturalized and common along roadsides, in dry pastures, and in open, mesic shrubland" in Hawai‘i (Wagner et al., 1999).

Erechtites hieraciifolius (fireweed) [voucher 9840] was found along the compact road in Melekeok State, possibly introduced with roadside seeding. This species is invasive in Hawai‘i (Wagner et al., 1999) and elsewhere.

Leucas lavandulifolia [voucher 9929] was found naturalized in a garden near Airai. It was previously recorded by Fosberg et al. (1979).

A potentially weedy yellow daisy, Melampodium divaricatum, (blackfoot, golden button) was found planted as landscaping at the Capitol [voucher 9846]. It is native to Central and South America and GRIN (USDA, 2008) reports that it is naturalized in the West Indies and Myanmar.

Pistia stratiotes (duckweed, water lettuce) was seen in cultivation at a house in Airai. This is a very dangerous species, invasive and listed as a noxious weed in many locations around the world. It poses a threat to Palau’s rivers and reservoirs. The weed risk assessment for this species rates it as high risk with a score of 18.

Pithecellobium dulce (kamatsíri, Madras thorn) was seen in cultivation in Airai State. It was previously reported from Koror but was not found in the 2002 survey. Spread by birds, it is invasive in Hawai‘i and to some degree on Guam and some other Pacific islands. It has a weed risk assessment score of 14, "high risk".

The naturalized ferns Pityrogramma calomelanos (silverback fern) [voucher 9837] and Pteris vittata (Chinese ladder brake) [voucher 9851] were recorded. The latter is naturalized in Hawai‘i (Oppenheimer, 2004; Palmer, 2003). These are not new introductions but were not noted in the previous survey.

Senna surattensis (scrambled eggs) was noted in cultivation in Aimeliik State [voucher 9924]. It is invasive in Hawai‘i. There, Motooka et al. (2003), reported that it "shades out forages in mesic pastures".

The grass species Setaria sphacelata (African bristle grass, golden timothy) was collected along the airport runway, forming clumps [voucher 9835]. It was previously reported by Fosberg et al. This species is invasive in mesic pastures in Hawai‘i (Starr, Martz & Loope, 2000).

Stapelia gigantea (carrion flower, giant toad plant) was noted as a potted plant at the Capitol. It is invasive in drier areas in Hawai‘i.

Striga asiatica (Asiatic witchweed), a parasitic plant, was found at the Badrulchau overlook on the north extension of the Compact Road [voucher 9895]. It was reviously recorded from Palau (Koror) as Striga lutea (Fosberg et al., 1979). This species can be a serious problem for agriculture. It can infest a wide range of grass crops (maize, millet, rice, sorghum, sugarcane) and some broadleaf crops (sunflower, tomatoes, some legumes) (Waterhouse & Mitchell, 1998).

Planted specimens of Timonius timon (Liberal) were found at three sites in Airai State [voucher 9902]. Two sites were single trees, but there were multiple trees and some apparent reproduction at the third site. From discussion with the owners of two of the sites it is apparently being brought from Peleliu by people nostalgic for their home island. In addition to becoming naturalized, there is a risk that T. timon may hybridize with endemic Timonius species growing nearby.

Scattered individuals of Xenostegia [=Merremia] tridentata (African morningvine) [voucher 9906], probably introduced and previously recorded (Fosberg et al. (1979); Fosberg, Otobed et al. (1980)) were found growing along with Anisea martinicensis in a hydroseeded area along the Compact Road.

Zornia gibbosa is present along the Compact Road in Airai State [voucher 9817] and in cultivation in Aimeliik State.

Koror State

Koror

Calathea majestica [=C. princeps], probably an escape from cultivation, spreads by rhizomes. While a Hawai‘i/Pacific risk assessment performed for this species indicates that it is of low risk based on the information available, it should be monitored for spread.

Several examples of Calliandra surinamensis (pink powder puff) were seen in cultivation. It is reported to be an invader in Fiji.

Livistona chinensis (Chinese fan palm, fountain palm) was seen in cultivation. It is known to be invasive in Florida and Hawai‘i. The Hawai‘i/Pacific Islands weed risk assessment for this species gives a score of 5, "evaluate further".

A newly naturalized Convolvulaceae species for Palau, Merremia hederacea (ivy woodrose) [voucher 9708] was found down the road from the Yuhi Hotel, climbing over trees and other vegetation. This was the only infestation of this species observed. From the size of the infestation it was probably present but missed in the previous survey. It was previously recorded from Guam and Yap in Micronesia (Fosberg et al., 1979). It is native to the Philippines and may have been introduced from there.

Pilea nummulariifolia (creeping Charlie) is probably an escape from cultivation on Koror. It spreads vegetatively. While it has a risk assessment score of 0 ("low risk") it should be monitored for spread.

Ngerkebesang

An example of Costus woodsonii (Indian-head ginger, red cane) in cultivation was seen and collected [voucher 9721]. The plant spreads vegetatively by forming new plantlets and may also spread by rhizomes. It has spread quite widely in the Lyon Arboretum in Hawai‘i, suggesting that it may also spread by seed (Daehler & Baker, 2006). It has a risk assessment score of 11, "high risk".

Episcia reptans has been planted at the Palau Pacific Resort [voucher 9720]. Small examples were also seen in cultivation and as a garden escape in Koror and in Airai State, Babeldaob. This species, with variegated leaves and a pretty red flower, is an attractive bedding plant and is thus likely to become widespread through cultivation. It is shade-tolerant and spreads aggressively by stolons. It can probably be easily transplanted and forms a dense ground cover. It is highly likely to spread outside of cultivation, crowding out native plants and inhibiting regeneration.

Rock Islands

We were especially interested in evaluating changes in the Rock Islands as a result of tourism and revisited nine of the islands that were surveyed in 2002. We also visited an additional island that had recently been opened to the public.

Ngemelis: This island has been recently opened to public use. It provides a dramatic example of the introduction and spread of Erigeron bellioides. This species was obviously introduced in one place but is now a patch about 20 feet in diameter growing on moist sand and undoubtedly will continue to spread [voucher 9864]. Other than that there were just some grasses and ruderal weeds.

Bab el Omekang: We found a few new grasses and ruderal weeds, some of which may have been missed last time.

Bkul a Chesemiich: Here we also picked up a few new grasses and ruderal weeds, some of which may have been missed last time. Timonius timon is present but has not increased since 2002.

Ngchelobel: New species were grasses and ruderal weeds, some of which may have been missed last time. Timonius timon is present but has not increased since 2002.

Ngchus: No change from previous survey.

Ngeanges (Neco): In 2002 this site was heavily used. It is now apparently hardly used at all and the buildings are abandoned. Hemigraphis reptans previously present was not seen but Timonius timon has seeded in prolifically on previously disturbed areas. Canavalia cathartica [voucher 9881] is also very prevalent in the previously disturbed area but is native (and previously reported from this island by Fosberg et al. (1979)).

Ngerchong: This island has houses and gardens unlike most of the other Rock Islands visited, which are mostly day-use sites. We found some new grasses and ruderal weeds, some of which may have been missed last time. Timonius timon is present but has not increased since 2002. Abroma agusta (Malvaceae) [voucher 9875], which is likely indigenous, and the cultivated Alternanthera ficoidea ‘Bettzichiana’ [voucher 9869] were collected. Bidens alba is new to this site. Sesbania grandiflora was noted in cultivation. Turnera ulmifolia is new to this island, apparently recently introduced.

Ngeremdiu: Part of the "Survivor" TV series was filmed on this island and we found two invasive species in the disturbed area: Echinochloa colona [voucher 9885] and Bidens alba. Both specimens were pulled and properly disposed of. Chamaesyce thymifolia was found on this site but possibly was missed in the previous survey.

Ngidech: Nothing new was found by the survey team at this site. Joel Miles (pers. com.) reports that he has been visiting Ngidech at least twice a year to extirpate the Chromolaena odorata plants discovered during the previous survey. During his last visit he found only about a dozen plants and, by continuing to prevent seed production, the infestation should be gone within a few years.

Peleliu State

Peleliu

Ammannia baccifera (amania, monarch redstem) [voucher 9749] is a weed of wet areas. It is a native of India and was previously recorded from Palau by Fosberg et al. (1970) as A. coccinea.

Barleria lupulina (hophead, Philippine violet) was seen in cultivation in the village [voucher 9765]. It was also seen in the 2002 survey on Babeldaob. This species is reported to be a problem in Timor and Queensland, Australia (Barbara Waterhouse, pers. com.).

Several plants of Crotalaria retusa (devil-bean, rattlepod, wedge-leaf crotalaria) were seen at the Dolphin Bay Resort [voucher 9740]. These were planted from seed as an ornamental according to the owner. This species was previously reported from Guam (Fosberg et al., 1979) and Yap (Belau National Museum, 1968, voucher 1249) but is a new record for Palau. Like other crotalarias, it could spread widely along roads and into disturbed areas. The plant is poisonous and consumption of the seeds could present a risk to chickens, pigs and humans. It has a weed risk assessment score of 5, "evaluate further". The owner seemed amenable to removing the plants if replacements could be provided. It must also exist elsewhere in Palau as the owner stated that the seeds were obtained locally, perhaps from Koror or Babeldaob, and the species should be looked for there.

Ngercheu (Carp Resort)

This resort has been very active in landscape planting; many exotic species were noted in the 2002 survey. New species noted this time include Callisia fragrans, Datura metel, Erigeron bellioides, Euphorbia graminea [voucher 9855], Ficus benjamina, Hemigraphis reptans, Melia azedarach, Oldenlandia [=Hedyotis] corymbosa, Passiflora foetida, Pedilanthus [=Euphorbia] tithymaloides, Pereskia aculeata and Pseuderanthemum caruthersii. Datura metel, Ficus benjamina, Melia azedarach and Pereskia aculeata are of particular concern as invasives, the latter a new record for Palau. Timonius timon [voucher 9855] is present on the island.

Kayangel

A number of new species were recorded from Kayangel. However, this is the first time much surveying and collecting has been done in recent times, so this is not surprising. Most of the new species are roadside and garden weeds or cultivated plants, including Abelmoschus moschatus [voucher 9796], Acalypha lanceolata [voucher 9799], Achyranthes aspera [voucher 9803], Asystasia gagetica [voucher 9780], Axonopus compressus [voucher 9798], Bidens alba [voucher 9781], Blechum pyramidatum [voucher 9824], Capsicum frutescens, Chamaesyce hirta, Chamaesyce hypericifolia [voucher 9793], Dactyloctenium aegyptium [voucher 9825], Digitaria ciliaris [voucher 9823], Erigeron bellioides, Ischaemum polystachyum [voucher 9779A], Malvaviscus penduliflorus [voucher 9806], Moringa oleifera, Oplismenus compositus [voucher 9778], Paspalum conjugatum [voucher 9827], Peperomia pellucida [voucher 9797], Pilea microphylla, Polyscias guilfoylei, Polyscias scutellaria, Pseuderanthemum carruthersii, Tabebuia heterophylla [voucher 9792], Tecoma stans, Thevetia peruviana, Thunbergia sp. and Turnera ulmifolia.

2. Species that are subjects of eradication programs

Imperata cylindrica (kasoring, blady grass, cogon grass), a very invasive grass and a serious problem for agriculture as well as the environment, is present around the airport on Babeldaob, as well as one location in Melekeok State and another suspected (non-flowering) infestation in Ngerkebesang. It is also reported to be present on Angaur but was not seen by the survey team. It has a weed risk assessment score of 22, "high risk". Eradication has been under way for five years but the grass keeps recurring from seed and from rhizomes that have not been killed. Eradication will require long-term follow-up to eliminate this persistent grass.

Mikania micrantha (teb el yas, mile-a-minute weed), a smothering vine, is widespread throughout the Pacific and is a major pest wherever it occurs. It is spread both by seed (dispersed by wind, as a contaminant on vehicles and machinery or on clothing or in the hair of animals) and vegetatively from broken stem fragments. Each node of the stem can produce roots. It was previously widespread on Koror and Ngerkebesang and also found on Babeldaob (Airai and Ngaraard States). A number of infestations, several quite extensive, were found on Peleliu during the 2002 survey, particularly in taro patches. An eradication program has made significant progress in decreasing the number and size of infestations but new patches continue to be found and some infestations, particularly those in taro patches, recur. The weed is particularly hard to eliminate in taro patches since they must be hand-weeded.

Schefflera actinophylla (octopus tree) was formerly present in cultivation. All known examples have been eradicated and no new ones were found during this survey.

Spathodea campanulata (orsachel kui, African tulip tree) was used to a limited extent in Palau as an ornamental tree. It is a major problem in Fiji, the Hawaiian Islands and some other places. The seeds are wind-dispersed and it also propagates from root suckers and cuttings. Large trees do not stand up well to wind. It has a weed risk assessment score of 14, "high risk". All infestations except one have been eliminated and there are ongoing negotiations with the landowner to remove the remaining trees. No new examples were found during the survey. Follow-up and destruction of seedlings or sucker regrowth in the vicinity of destroyed trees should be continued.

Indigofera hirsuta (hairy indigo), Ipomoea hederifolia (ivy-leaf morning glory) and Praxelis clematidea (praxelis) were apparently introduced during the construction of the Compact Road, most likely from contamination of the seed used in hydroseeding. They were found in isolated patches and have apparently been eradicated. However, the praxelis had produced seed at one site, and regular inspection of the sites should be continued for at least the next few years.

3. Major species that are invasive or have the potential to become so in Palau

A number of known invasive plants that cause trouble in natural and semi-natural ecosystems have been introduced into Palau (Appendix 1 Table 2). Some of these are already causing problems while others are naturalized but are not causing any particular problem. Some are cultivated plants that have not (yet) escaped and their potential for causing damage is so far unknown. However, one of the best predictors of invasiveness is the behavior of the species elsewhere under similar conditions, and these are known troublemakers.

Invasive species already widespread in Palau

A number of serious invasive species are already widespread in Palau. Eradication or extensive control is out of the question for these species, but they may still warrant control in sensitive, natural and protected areas such as parks and reserves.

Adenanthera pavonina (telengtúngd, telentundalel, coral bean tree), invasive in secondary forests throughout the Pacific, is common in Palau. Although the seeds are eaten and many people consider it native, it was introduced. Coral bean has the ability to overtop many native trees and eventually form monospecific stands. Trees produce large quantities of seed and the tree will grow on a variety of soils. While it seems to be scattered at the present time, if its behavior on Palau is similar to other Pacific locations, it may eventually become much more widespread. Its weed risk assessment score is 7, rating it "high risk".

Allamanda cathartica (allamanda, yellow trumpet vine) is widely planted and naturalized. It is becoming invasive in northern Queensland, Australia, and Papua New Guinea. The 2002 survey noted its presence in forest and savanna in central Babeldaob. It has a risk assessment score of 8, "high risk".

Arundo donax (giant reed) is found in moist areas and along ditches and riverbanks. "Once established, giant reed can form huge clones, sometimes covering hundreds of acres. It is highly flammable and re-sprouts quickly after burning. Fires help transform communities of native plants into solid stands of giant reed, changing riverbank forests from flood- to fire-defined habitats" (Bell, 1996). It spreads by means of rhizomes and fragments of stems, often carried by water and has a weed risk assessment score of 12, "high risk".

Chromolaena odorata (ngesngesil, chromolaena, Siam weed) is a highly invasive pan-tropical weed that is widespread in Palau. It has small, wind-dispersed seeds that can also travel on boots, clothing or used cars or equipment. The biological control agents Pareuchaetes pseudoinsulata (a moth) and Cecidochares [=Procecididochares] connexa (Tephritidae) (a gall fly) have been introduced to Palau (Muniappan and Marutani, 1991). Pareuchaetes pseudoinsulata is not established. Cecidochares connexa is established in Koror State and Babeldaob and appears to be reducing flowering and plant vigor. In addition to the widespread infestations of chromolaena on the main islands, a small infestation was found in 2002 on Ngidech in the Rock Islands and is in the process of being eliminated. An Australian risk assessment gave this species a score of 34, indicating that it is of very high risk.

Clerodendrum quadriloculare (kleuang, bronze-leaved clerodendrum) was common in 2002 but has been reduced since that time by control action. The species is often planted as an ornamental but is notorious for being a prolific producer of root suckers and, in fact, the plant is easily propagated by means of root cuttings. It has the ability to invade intact or relatively intact native forests. It has become widespread on Pohnpei, Federated States of Micronesia. In Hawai‘i it is becoming a problem ornamental, producing numerous root suckers that appear some distance from the parent plant. There are still occasional infestations in yards and along roadsides. The weed risk assessment for this species indicates that it is "high risk", with a score of 11.

Clidemia hirta (kúi, Koster’s curse) is a serious problem species in Hawai‘i and other locations, including Fiji, the Solomon Islands and Vanuatu. It is a very serious weed of the forest understory on a number of tropical islands. It is shade tolerant, is spread by birds and has the potential to invade all the forests of Palau. It was thought to be confined to a single area on Babeldaob near the Forestry Station at Nekken (in the vicinity of old Oikull Village in Airai), but during the 2002 survey a single plant was found on the hill above the radio tower on Malakal. That plant was destroyed and the area searched for others. This area was revisited in 2008 and no new plants were noted. The weed risk assessment for this species is "high risk", with a score of 27. A biological control agent, Leothrips urichi, was introduced to Palau in the late 1960’s, is established and effective in open areas but largely ineffective in forested habitats.

While it is mostly used as a cultivated ornamental, a large number of escapes of Dieffenbachia seguine (spotted dieffenbachia, dumb cane) were noted, probably as a result of discarded plants or cuttings. This species can be invasive and difficult to remove, particularly along streams and other moist areas. It has become a major problem in this regard in American Samoa and Samoa. Where found outside of cultivation, particularly in wet areas, this species should be removed, as it reproduces vegetatively and can thrive in the dense shade of an intact native forest canopy, crowding out other species. The weed risk assessment score for this species is 7, "high risk".

Dissotis rotundifolia (dissotis, pink lady) was seen in cultivation and infestations are common, particularly on Babeldaob. It can form a dense mat in the forest understory, crowding out or excluding other species. This behavior was seen in Samoa. It is a problem species as well in Fiji, French Polynesia and Hawai‘i. Since it can reproduce vegetatively, mowing or slashing can spread it more widely or lead to very dense stands. Its weed risk assessment score is 10, "high risk".

Falcataria moluccana [=Paraserianthes falcataria] (ukall ra ngebard, Moluccca albizia) is most common in central Babeldaob although it was also seen on Koror. Many of the trees are quite large and apparently have been present for some time. Some of the older trees have recently died. Some younger trees were noted becoming established in disturbed areas on the edge of the forests. It is much more aggressive and extensively naturalized on Pohnpei (Federated States of Micronesia), Tutuila (American Samoa), Kauai (Hawaii) and Tahiti (French Polynesia). It has a weed risk assessment score of 8, "high risk".

Lantana camara (lantana) is common, both cultivated and naturalized. Wild plants seem to be more common on the northern part of Babeldaob and on Koror and Angaur. A pink form is prevalent in northern Babeldaob and Angaur while a red form is present in Koror and surrounding areas. At least two biological control agents have been introduced, but their present status is unknown. In any case, Lantana doesn’t seem to be a big problem in Palau at the present time, although its weed risk assessment score is 21, "high risk".

Leucaena leucocephala (telengtungd, leucaena) is very common, as on most Pacific islands, but it is not as prevalent in Palau as it is in many other locations. It is a prolific seed producer, with a weed risk assessment score of 15, "high risk".

Mimosa diplotricha [often incorrectly called M. invisa] (mechiuaiuu, giant sensitive plant) is a particularly nasty plant covered with brittle thorns, forming dense tangles that are difficult to walk through. It is present in a number of South Pacific locations (American Samoa, Cook Islands (Aitutaki), Fiji, French Polynesia (Society Islands), New Caledonia, Niue, Papua New Guinea, Solomon Islands and Vanuatu). Biological control agents were reportedly introduced to Palau, but it is not known if they have become established. If present, they seem to be having little effect. It is fairly common on Babeldaob and a number of infestations were noted along the Compact Road. The species is only present to a limited extent on Angaur and is absent from Peleliu. It has a weed risk assessment score of 24, "high risk".

Mimosa pudica (sensitive plant), a smaller plant than M. diplotricha with only small thorns, is common throughout Palau (except Peleliu) as a component of the weedy vegetation of roadsides and other disturbed areas. It has a weed risk assessment score of 18, "high risk".

Pennisetum polystachion (desum, mission grass) is commonly found in disturbed areas. It provides fuel for fires and readily spreads after fire, perpetuating a fire cycle. This species has seeds adapted for dispersal by wind and is frequently spread as a contaminant on vehicles and machinery. Its weed risk assessment score is 11, "high risk".

Psidium guajava (guabang, kuabang, guava) is common in cultivation and is occasionally present as naturalized plants, but nothing like the dense stands seen in Tonga. This is a major invasive species in Tonga and the Galapagos Islands as well as a problem in French Polynesia (Marquesas Islands), New Caledonia, Hawai‘i and Fiji. Frugivorous birds, as well as rats and feral pigs, disperse the seeds. However, in Palau it does not seem to be any more common than in 2002 even though it has a "high risk" weed risk assessment score of 21.

Sphagneticola [=Wedelia] trilobata (ngesil ra ngebard, Singapore daisy) has become a serious pest on many Pacific islands (Thaman, 1999) as well as in northern Australia. It is both planted and naturalized at a number of locations throughout Palau. It can form dense mats along roadsides and in disturbed areas and is a problem in agriculture. Control by chemical means is difficult and mechanical removal often leaves numerous nodes that freely root and rapidly spread. Mowing or slashing can make the problem worse unless done very frequently and very close to the ground. Its weed risk assessment score is 13, "high risk".

Tecoma stans (yellow bells, yellow-elder, yellow trumpetbush) is widely cultivated in Palau. It is a serious invader of disturbed areas in Tonga and French Polynesia where it grows in dense stands, commonly with other weedy species. The seeds are wind-dispersed. However, only isolated individuals were seen outside of cultivation. It is a "high risk" species with a weed risk assessment score of 8.

Thunbergia grandiflora (bung el etiu, blue trumpet vine, Bengal trumpet) is an aggressive vine that can smother trees. The plant forms large underground tubers and is difficult to eradicate because of regeneration from the tubers and root and stem fragments. It is a problem species in Australia (a noxious weed in Queensland) and Singapore. It has a weed risk assessment score of 11, "high risk". There were formerly a number of examples in Palau, including a very large infestation in Koror, but its presence has been reduced by control action since the 2002 survey. However, much work remains to be done on this plant.

Timonius timon (Liberal) is widespread on Angaur and Peleliu. Individual trees and small stands were found on a number of the Rock Islands. It was probably introduced to Angaur and Peleliu during or shortly after World War II and has since spread to the Rock Islands. Several individual trees and an apparently reproducing infestation were located on Babeldaob. Single trees (possibly planted) were previously observed on Kayangel and Ngerkebesang. It is an invader of open, disturbed areas. As time goes by, it seems to be overtopped and replaced by native species, and it seems to be less prevalent on Angaur and Peleliu than formerly as these forests have become more mature. Its presence in the Rock Islands indicates that it is spreading to the north and, unless checked, will probably eventually reach Koror and Babeldaob where it would probably be an invader in open and disturbed areas and potentially hybridize with endemic species of Timonius.

Tradescantia spathacea (kobesos, oyster plant, boat plant, boat lily, Moses in a boat) and T. zebrina (wandering jew) are planted as ornamentals in Palau but have escaped in several instances. Several examples of Tradescantia spathacea invading the forest understory were seen on Peleliu. A fairly large patch of naturalized Tradescantia zebrina can be seen in Ngiwal State, Babeldaob, as well as on Angaur. There is a small naturalized patch on Kayangel. These plants are commonly spread through the dumping of garden cuttings.

Turnera ulmifolia (yellow alder, sage rose) is widely planted as an ornamental. Naturalization was noted at a number of locations. The seed is reported to be carried by ants (Staples et al., 2000) and the species is widely naturalized in the tropics. A related species, Turnera subulata (white alder), was also noted in cultivation. This species is somewhat weedy in Malaysia and has a weed risk assessment score of 10, "high risk".

Invasive species of limited extent

The following species are limited in extent or have recently become established. Some of them are only in limited cultivation and could be eradicated at minimal cost. Others may be candidates for control action or should just be monitored for possible future action, if necessary. See the recommendations section for species-specific recommendations.

Acacia [Vachellia] farnesiana (Ellington curse, klu, sweet acacia) was seen at one location in cultivation in Airai State, Babeldaob, during the 2002 survey. This thorny shrub is a pest in Fiji, French Polynesia, New Caledonia, Solomon Islands and Vanuatu and has a "high risk" weed risk assessment score of 14.

Alternanthera brasiliana (Brazilian joyweed, Joseph’s coat) is planted as an ornamental and occasional escapes were seen. It is invasive in Queensland, Australia.

Antigonon leptopus (dilngau, chain of love), a climbing vine often planted as an ornamental, is a widespread pest on Guam. Although this species has been subject to control action, several examples, mostly in cultivation, were seen in Koror. It is a "high risk" and difficult to remove species with a weed risk assessment score of 19.

A few examples of Asparagus densiflorus (asparagus fern, sprengeri fern) were seen, all in cultivation (often in hanging baskets). Asparagus densiflorus has recently been found to be rather widespread in Hawai‘i on the island of Kauai. There it is spreading along roadsides, in hedges and invading secondary forest. It seems to have the ability to withstand herbicide treatments used to control vegetation along roads. The seeds are bird-dispersed, and it can also spread vegetatively through root tubers from discarded plants, among other characteristics giving it a "high risk" weed risk assessment score of 15. On several islands in Tonga, the thorny vines of a closely related species, Asparagus setaceus (not found in Palau), have become established in the forest understory, climbing into the canopy. Both species are commonly sold as ornamentals.

What are probably the remnants of an old rattan (Calamus sp.) (bangerenguis ra ngebard) plantation is present in Aimeliik State, Babeldaob. Not only is this species invasive, but its spine-armed stems and pairs of hooked flagellae extending from the leaves make travel where it is present difficult and painful.

Cinnamomum verum [=C. zeylanicum] (ochod ra ngebard, cinnamon) was reported present by Fosberg et al. (1979) but was not seen in the previous or present survey or in the botanical survey of the Compact Road (Raulerson et al., 1996). If present, this is a potentially dangerous species. It is actively invading secondary forests in American Samoa and Samoa. It is also present and invasive in the Cook Islands (Rarotonga), Fiji, French Polynesia, Hawai‘i and Mauritius. Its weed risk assessment score of 10, although rating "high risk" may not fully reflect its invasiveness and potential for damage based on observed behavior elsewhere in the Pacific region.

Cyperus involucratus [=C. alternifolius subsp. flabelliformis] (deus, umbrella sedge) was seen in cultivation at one location in Koror in the 2002 survey. While no examples were seen in this survey it is likely to still be present as it is often planted as an ornamental. It has a weed risk assessment score of 17 "high risk" and can be an invader in wet areas, especially along streams and rivers.

Datura metel (downy thorn-apple, jimson weed), found on Ngercheu Island (Carp Resort), is a prolific seed producer that is naturalized and invasive in Hawai‘i, Fiji and Niue. It is also present on Angaur, Peleliu, Babeldaob and Malakal. A weed risk assessment from Australia gives this species a score of 21, making it high risk.

Eichhornia crassipes (bung el ralm, water hyacinth) was seen in cultivation on Koror, Ngerkebesang and Babeldaob in the 2002 survey. Water hyacinth is a well-known problem worldwide in freshwater lakes, ponds, marshes, ditches, canals and slow-moving streams. It reproduces both by seed and vegetatively. Its weed risk assessment score of 14 makes it of high risk.

Elaeocarpus angustifolius [=E. grandis] (blue fig, blue marble tree, quandong), a native of Australia, is a forestry tree that is invading intact and secondary forests in Samoa. It is reported present in Palau (Fosberg et al., 1979), perhaps in old forestry trials on Babeldaob, but was not seen on this or the 2002 survey.

Epipremnum pinnatum ‘Aureum’ [=Scindapsus aureus] (pothos, money plant) is present at a number of locations throughout Palau but most common in Koror and Airai States, including a patch invading Rock Island forest behind the office of The Nature Conservancy. It is mostly in cultivation but this tree-climbing species can invade the forest understory. It is a cultivar of a native plant (Epipremnum pinnatum) but is not native to Palau, apparently originating in the Solomon Islands (Smith, 1979) and widely cultivated. Since it only reproduces vegetatively from cuttings and pieces, the main concern is infestations that become established in the forest. Its main method of spread is through discarded garden cuttings. It has a weed risk assessment score of 9, "high risk".

Eugenia uniflora (Surinam cherry), a small tree sometimes cultivated as an ornamental, is present on Koror. It was observed spreading on the islands of Mangaia and Ma‘uke, Cook Islands and is naturalized on Mauritius. Fruit-eating birds (and humans) probably spread the seeds.

Flemingia macrophylla was seen in cultivation on Koror and in Airai State, Babeldaob, during the 2002 survey. This species is a prolific seed producer and can form dense thickets. It is invasive in Samoa and the Cook Islands. It has the potential to become a serious problem if it escapes cultivation. A related species that is invasive in the South Pacific as well as in Mauritius, Flemingia strobilifera (besungelaiei, luck plant, wild hops), is also present on Babeldaob, Koror and Ngerkebesang.

Hedychium coronarium (white ginger) was seen in cultivation on Koror, on Ngerkebesang and in Airai just beyond the Koror-Babeldaob bridge. This and other Hedychium species can be quite invasive in wetlands and in moist areas under the forest understory and are difficult to control. Hedychium species have become extensively established in Hawai‘i, where they are a major problem. It is a "high risk" species, with a weed risk assessment score of 10.

Hevea brasiliensis (Brazilian rubber tree, Para rubber tree) is reported present in Koror (Fosberg et al., 1979) and in Nekken, Babeldaob (per Marcello Brel), but was not seen either in 2002 or during this survey. This species is reported to be naturalizing in Papua New Guinea and on Christmas Island (Indian Ocean).

Hyptis pectinata (mint weed) was seen in Ngatpang State in 2002 but was not relocated in this survey. It was also recorded on Angaur (Fosberg et al., 1979) but was not seen there in either survey. Its seeds stick to clothing and to the fur of animals and can also be spread by vehicles and machinery. It is on the Hawai‘i State noxious weed list, is a noxious weed in Fiji, is very prevalent in Samoa and is becoming so in Tonga. It is a serious weed of disturbed sites and agriculture.

Ipomoea quamoclit (asangao, star of Bethlehem, Cupid’s flower, cypress vine) was seen growing in a vacant lot at New Ngatpang and as a cultivated plant in Koror during the 2002 survey. This species is invasive in Fiji and north Queensland, Australia. It has a risk assessment score of 14 and is thus rated "high risk".

Melaleuca quinquenervia (cajeput, paper bark tree) is a native of eastern Australia, New Guinea and New Caledonia. It produces large quantities of wind-dispersed seeds and reproduces profusely after fire or other disturbance. Large numbers of seeds are stored on the tree in the fruiting capsules and are released when fire or other disturbance occurs. It is a major problem in the State of Florida (US) and is present and naturalizing to some degree on Yap. The tree has been planted on Babeldaob and is reproducing. Much more prolific reproduction can be expected if a fire occurs. It has a weed risk assessment of 15, "high risk".

Melia azedarach (Chinaberry, pride-of-India, Indian lilac) seedlings were seen beneath and around cultivated plants at a residence and a business in Airai in the 2002 survey. It was also seen in cultivation on Koror. Several seedlings were also noted in Koror that appeared to be self-sown, but the source was not immediately apparent. In this survey, the species was noted in cultivation on Malakal (in the gardens near the radio tower), at several additional residences in Airai and on Ngercheu Island (Carp Resort). This species is a prolific producer of seed, which is spread by birds. In Palau, it apparently begins to flower at a very young age. It is invasive in a number of Pacific locations, including the Cook Islands, French Polynesia and Hawai‘i as well as in South Africa. It is a "high risk" species with a weed risk assessment score of 14.

Melinis minutiflora (molasses grass) is a species that is particularly dangerous in that it is both invasive and can cause a serious fire hazard. It has modified fire regimes on many islands where it has been introduced (D’Antonio and Vitousek, 1992) and it is reported as a serious threat to forests in Brazil (C. Martins, pers. comm.). It was reported present by Fosberg et al. (1979). Raulerson et al. (1996) reported it present on Babeldaob but rare. We found it on the north extension of the Compact Road in Ngaraard State. An Australian weed risk assessment gives this species a score of 7, indicating it is of high risk.

Panicum maximum [=Megathyrsus maximus, Urochloa maxima] (Guinea grass), while not yet widespread in Palau (it is present on Koror and Babeldaob), is another grass that can help perpetuate a fire cycle. It seeds profusely and the seeds are dispersed by wind, birds (e.g. chestnut mannikins) and flowing water or as a contaminant. It can survive long periods of drought. Fire will sweep through stands of this grass but it regenerates rapidly from underground rhizomes. It is a problem species in Guam and Hawai‘i and is very prevalent in Samoa and Tonga, forming dense stands in open and disturbed areas. Its weed risk assessment score is 17, "high risk".

Pennisetum setaceum (fountain grass) was found in cultivation at two residences in Airai and a resort in Ngerkebesang in 2002 but was not seen in 2008. It is an attractive ornamental but it can produce large amounts of wind-dispersed seed. While it is most likely to be invasive in dry areas, it could possibly spread in Palau. It is a serious problem species on dryer sites in Hawai‘i. It has a weed risk assessment score of 26, "high risk".

Pereskia aculeata (Barbados gooseberry, leafy cactus) was found on Ngercheu Island (Carp Resort). It is invasive in Queensland, Australia, particularly in riparian areas, forming large, impenetrable clumps. It is a declared noxious weed in South Africa, where it has become a problem in forestry and conservation areas. Seed is bird-dispersed and it can also spread from stem fragments. Its weed risk assessment indicates that it is of high risk, with a score of 13.

Pluchea carolinensis (sour bush) and P. indica (Indian fleabane, Indian pluchea, Indian camphorweed) are present on Peleliu and P. indica is present on Angaur. They are shrubby species with wind-dispersed seed. Pluchea carolinensis is naturalizing extensively on Tongatapu, Tonga, and is reported to be widespread but not presently abundant on Guam. These species may have been accidentally introduced as a result of military activity as both were also introduced to Penrhyn Island (Cook Islands) when an airfield was built there during the Second World War (Bill Sykes, pers. com.) and are present elsewhere in the Pacific where military airfields were constructed. Pluchea indica is found along the seashore and inland on poorer sites on both Peleliu and Angaur while P. carolinensis is located along the airstrip on Peleliu.

Pithecellobium dulce (kamatsíri, opiuma, Madras thorn) is a thorny tree that is a problem species in Hawai‘i. It is present on many of the major islands of Micronesia, but doesn’t seem to be a serious problem. The seeds are bird-dispersed and its sap can cause eye irritation and skin welts. It is relatively resistant to fire and resprouts rapidly by basal or aerial shoots. It was reported cultivated on Koror by Fosberg et al. (1979) but that tree has not been seen in recent surveys. A planted tree was seen in Airai during this survey. Its weed risk assessment gives it a score of 14 and rates it "high risk".

Psidium cattleianum (strawberry guava), a small tree that forms dense thickets, was previously reported to be present on Koror (Fosberg et al., 1979), perhaps in cultivation, but was not found during this or the previous survey. It is a major problem species in a number of island ecosystems including Hawai‘i and Tahiti in the Pacific and La Réunion and Mauritius in the Indian Ocean. Varieties with red and yellow fruits are known. Birds and pigs (and possibly fruit bats as well) disperse the seeds. This is an extremely dangerous species with a weed risk assessment score of 18.

Solanum torvum (prickly solanum, devil’s fig) is a large spiny shrub of disturbed areas and fields that can form dense, impenetrable thickets. Its seeds are bird-spread. The principal infestation (apparently a number of individual plants) is in and around Nekken in Ngatpang and Aimeliik States, Babeldaob. A leaf-eating chrysomelid beetle, Leptinotarsa undecimlineata, is reported to be host-specific (Waterhouse and Norris, 1987) but would probably not be effective on the scattered plants found on Babeldaob.

Syngonium angustatum (arrowhead plant, goosefoot plant), a climbing aroid, is widely cultivated in Palau, particularly in Koror and Airai States, and a number of escapes were noted both in this and the previous survey. This species has the ability to spread in the deep shade of intact forests, forming a dense mat on the forest floor as well as climbing trees. It is difficult to eradicate as it is able to reproduce from a single node and stem and root fragments are easily overlooked. It spreads vegetatively from dumped cuttings. It is a problem species in American Samoa, is widespread in Hawai‘i and is quite invasive in Niue. An almost identical species, Syngonium podophyllum, has a weed risk assessment score of 15, "high risk", that can also be applied to this species.

Syzygium cumini (mesekerrák, Java plum) is reported to be present, perhaps in cultivation, on Koror, Babeldaob and Aulupse‘el (Rock Islands) (Fosberg et al., 1979; Raulerson et al., 1996) but was not seen in either this or the 2002 survey. It was seen on several of the Rock Islands (including Bukrairong) by the second author in Jan. 2008 and appeared to be established but not particularly invasive. This species is invasive in the Cook Islands, Hawai‘i and French Polynesia (Raiatea).

Two small plants of Tephrosia candida (white tephrosia) were found in Aimeliik State on Babeldaob in 2002 and there are voucher specimens in the Bishop and Belau National Museums. It was searched for but not seen in 2008. This species has become established as a pest species on a number of Pacific islands. It can form dense thickets, particularly in disturbed areas. As it has been recorded as present in Babeldaob for a long time (Fosberg et al., 1979) it may not become a serious pest here although its risk assessment indicates that it is high risk with a score of 8.

Vitex parviflora (small-leaved vitex) was reported present in Palau by Fosberg et al. (1979), but has not been seen recently. It may be present in cultivation. It is a native of the Philippines, has bird-dispersed seeds and is invasive in Guam.

4. Other species of concern that are known to be weedy or invasive elsewhere and are common, weedy or cultivated in Palau

A large number of other common or weedy introduced species were noted. Many of these species might best be termed aggressive weeds, and are mostly prevalent along roadsides or on disturbed sites. In the case of vines and plants that form dense ground cover, the regeneration of native species might be inhibited if they became widespread. Quite a number of alien trees have also been introduced, some of which may have the potential to spread into forested ecosystems. Some species that are not widespread could become a problem in the future, since there is often a long lag time between introduction and when a species begins to cause serious impacts. The species thought to be of environmental concern are listed in Appendix 1 Table 3. When not already widespread, these species should be monitored and control measures instigated, if necessary. The more problematic ones are listed and discussed below. A number of other species, thought to be of low risk or agricultural concern, are listed in Appendix 1, Table 4.

Acacia auriculiformis (earleaf acacia, earpod wattle) is widely planted but in only a few cases were significant numbers of seedlings present, usually where mineral soil was exposed as a result of fire or other disturbance. However, it has a weed risk assessment score of 13, "high risk". Naturalization may increase with more disturbance or fire activity.

Spiny Barleria lupulina (hophead, Philippine violet) was seen in cultivation in Ngchesar State in 2002 and in Peleliu in 2008. The owner of the plant in Ngchesar destroyed it when asked to do so. The owner of the plant in Peleliu should be requested to do the same. It is invasive in Timor and some naturalization has been noted in north Queensland (Barbara Waterhouse, pers. com.) and Hawai‘i (Wagner et al., 1999).

Bryophyllum pinnatum [=Kalanchoë pinnata] (life plant) is present in cultivation and some seedlings were noted in the 2002 survey. Bryophyllum delagoense [=Kalanchoë tubiflora] (chandelier plant) was seen on Babeldaob in 2008 and likely is present elsewhere. Both these species reproduce vegetatively and can be invasive on the forest floor, particular on dry, rocky sites.

Calotropis gigantea (calotrope, crown flower, madar) is found in cultivation on Koror, Ngerkebesang, Babeldaob and Peleliu. It is an invasive species in Timor and has naturalized in northwestern Australia and some Hawaiian Islands.

Duranta erecta (golden dewdrop) is widely planted as an ornamental. It produces prodigious amounts of fruit and is reported to be naturalizing in Hawai‘i, Florida and Queensland, Australia). Its weed risk assessment classifies it as "high risk" with a score of 13, but we have not observed it being a problem on Palau or on other Pacific islands outside of Hawai‘i.

The African oil palm (Elaeis guineensis) is present on Koror and present and reproducing to some extent on Babeldaob. It has a risk assessment score of 9, "high risk", and thus should be monitored for spread.

Episcia cupreata (episcia, flame violet) is widely cultivated but is also growing wild on rock walls and in the forest understory, especially in Koror State. It has a risk assessment score of 3 so it warrents monitoring for spread.

Hemigraphis alternata (metal leaf, red ivy), introduced as an ornamental, is present in dense low stands at several locations, sometimes invading under the forest canopy. Although rated "low risk" with a risk assessment score of 1, it is shade tolerant, spreads in the forest understory over time and can exclude other species.

Hyptis capitata (knobweed) is widely distributed on Babeldaob, Koror, Malakal and Ngerkebesang. It is quite invasive along roads and in disturbed areas and has a score of 17 from a weed risk assessment prepared in Australia.

Inga edulis (ice cream bean) is a tree that is becoming invasive in northern Queensland. An example was seen in 2002 growing in front of Palau Community College. It has a weed risk assessment score of 2, "evaluate further". The identification on this tree should be checked as it may be I. feuillei.

Murraya paniculata (orange jessamine, mock orange, satin-wood, Chinese box) is cultivated as an ornamental plant. It has bird-dispersed seeds and thus the ability to spread and has a weed risk assessment score of 6 (evaluate further). However, it has not been observed as invasive on the Pacific islands where it is present. In Asia M. paniculata is the preferred host of the insect pest Diaphorina citri, the citrus psyllid. The psyllid is the vector for the serious citrus disease "huanglongbing".

Passiflora foetida (kudamono, love-in-a-mist) is widespread but does not appear to be highly invasive in Palau. It is quite prevalent on most Pacific islands and on some it is a serious pest.

Occasional cultivated plants and patches of Pseuderanthemum carruthersii are present on Kayangel, Ngerkebesang, Babeldaob, Peleliu and Tobi, but the 2002 survey reported it to be a problem on Sonsorol, where it is expanding into the forest along roads and paths.

Quisqualis indica (Rangoon creeper) was seen on a fence in Ngerkebesang in 2002 and at a residence in Aimeliik State in 2008. It is reported to naturalize in the tropics (reproducing from both seed and suckers), but has yet to become a problem in the Pacific region.

Ricinus communis (gelug, maskerekur, uluchula skoki, castor bean) is present along roadsides and in disturbed places on Peleliu and Angaur. This species has a weed risk assessment score of 21 and is a serious invader on some Pacific islands. It is not a serious pest on Peleliu and Angaur but might be more of a problem if introduced to Babeldaob where there are more open areas.

A single tree of Senna siamea (cassod tree, Siamese cassia) was seen in Ngeremlengui State, Babeldaob. It is invasive in Australia (Cape York Peninsula) and reported to be weedy in Tahiti.

Stachytarpheta cayennensis [=S. urticifolia] (louch beluu, blue rat’s tail, dark blue snakeweed) is very common in Palau as it is throughout the Pacific. While mostly a pest in open areas, it can invade into the forest, particularly when there has been disturbance. It is a "high risk" species based on its Australian weed risk assessment score of 20. Stachytarpheta jamaicensis (louch beluu, blue porterweed, light blue snakeweed) is also common and the two can hybridize. Both species are especially prevalent on Angaur and common on Babeldaob.

Some exotic tree species that have been introduced to Palau include Acacia confusa (ianángi, yanangi, Formosa koa), Acacia mangium (mangium), Albizia lebbeck (ukall ra ngebard, siris-tree, rain tree), Bauhinia acuminata (dwarf white bauhinia), Bauhinia monandra (orchid tree), Bauhinia purpurea (purple orchid tree), Bauhinia variegata, Ceiba pentandra (kalngebárd, kerrekar ngebard, kapok), Ficus sp., Ficus benjamina (weeping banyan), Gliricidia sepium (rechesengel, mother of cacao, quickstick), Muntingia calabura (budo, Panama cherry), Samanea saman (monkeypod), Senna surattensis (scrambled eggs), Sesbania grandiflora (katurai, hummingbird tree, scarlet wisteria tree) and Thevetia peruviana (yellow oleander). These species are known to naturalize and can be more or less successful depending on local conditions. In Palau, Acacia mangium is planted in a few locations, but the 2002 survey noted only a few seedlings adjacent to the small forestry planting in Aimeliik State. Muntingia calabura is very commonly naturalized along roadsides and in clearings. The rest of the above-mentioned trees seem to reproduce little or not at all in Palau, although some of them are of continuing concern based on their weed risk assessments and their behavior in other locations.

In addition to Arundo donax, Imperata cylindrica, Melinis minutiflora, Panicum maximum [Megathyrsus maximus, Urochloa maxima] Pennisetum polystachion and Pennisetum setaceum, discussed in the previous section, a number of other introduced grasses are established, including Bothriochloa bladhii, (desum, blue grass, Australian beardgrass), Cenchrus brownii (burr grass), Cenchrus echinatus (burr grass), Chloris barbata (swollen fingergrass), Chloris radiata (plush-grass, radiate fingergrass), Cynodon dactylon (Bermuda grass), Digitaria ciliaris (smooth crabgrass), Digitaria violascens (sau, smooth crabgrass, violet crabgrass), Eleusine indica (kelelamalk, keteketarmalk, goosegrass), Panicum repens (torpedo grass), Paspalum conjugatum (udel ra ngebei, T grass), Paspalum paniculatum (Russell river grass, galmarra grass), Pennisetum purpureum (bokso, elephant grass, napier grass, merker grass), Sorghum halepense (Johnson grass), Urochloa [Brachiaria] mutica (para grass) and Urochloa [=Brachiaria] subquadripara (green summer grass, tropical signalgrass). Bamboos (esel) (Bambusa spp.) are also present. Urochloa [=Brachiaria] decumbens (signal grass) was widely seeded for bank stabilization along the route of the Compact Road.

Other weedy species include Calopogonium mucunoides (calopo), Centrosema pubescens (centro), Chamaecrista mimosoides (Japanese tea), Chamaecrista nictitans (partridge pea, Japanese tea senna), Clerodendrum buchananii (butcherechár, red clerodendrum, pagoda-flower), Clerodendrum paniculatum (butcherechár, pagoda flower), Clitoria ternatea (kles, butterfly pea), Crotalaria micans (crotalaria), Cyperus rotundus (tamanengi, nut grass, nutsedge), Desmodium tortuosum (Spanish clover), Kyllinga brevifolia (esechesiding, green kyllinga), Leonurus japonicus (lion’s tail), Macroptilium atropurpureum (siratro), Macroptilium lathyroides (cow pea, phasey bean), Senna [=Cassia] obtusifolia (coffeeweed, sicklepod) and Senna occidentalis (coffee senna). Stylo (Stylosanthes guianensis) was extensively seeded for bank stabilization along the Compact Road.

Species that are cultivated or of limited extent but have the potential to become more widespread include Asystasia gangetica subsp. gangetica (Chinese violet, Philippine violet, coromandel), Nymphaea spp. (waterlily), Ocimum gratissimum (wild basil), Sanchezia parvibracteata (sanchezia), Schefflera arboricola (dwarf brassia, dwarf schefflera), Senna [=Cassia] alata (candle bush) and Tithonia diversifolia (tree marigold, Mexican sunflower).

5. Native species (or Micronesian introductions) exhibiting aggressive behavior

Casuarina equisetifolia (ngas, casuarina, ironwood, Australian pine) is native or an early introduction to the main islands of Palau, where it also appears to be widely planted. It is a recent introduction to Tobi and Helen’s reef. The 2002 survey found a single tree on Tobi that is not yet bearing fruit and a naturalized population on Helen’s Reef. The tree has a shallow root system and planting along beaches or other unstable areas is not recommended. The species is rated "high risk" where it is not native, with a risk assessment score of 21.

Chrysopogon aciculatus (iul, Mackie’s pest, lovegrass) is indigenous or an early introduction to the main islands but is a recent introduction to Sonsorol and Tobi. It is an aggressive, noxious weed that readily withstands trampling, poor soils and mowing. Its sharp seeds can penetrate flesh and work their way in, causing festering sores. Its spiked seeds are carried from place to place in fur, feathers, or clothing.

Other common native grasses (or early introductions) include Ischaemum polystachyum (paddle grass), Ischaemum rugosum (muraina grass), Ischaemum timorense (centipede grass), Saccharum spontaneum (banga ruchel, wild cane, false sugarcane), Sacciolepis indica (glenwood grass), Setaria pumila [=pallide-fusca] (foxtail) and Sporobolus indicus (smutgrass, wiregrass).

Ipomoea violacea (moon flower) is native throughout much of the Pacific region and present on the Rock Islands, Babeldaob and elsewhere. exhibits aggressive behavior (Smith, 1991; Whistler, 1992). It is "naturalized in wet sites, coastal areas, trailing over rocks or on sand" in Hawai‘i (Wagner et al., 1999). It should not be introduced to islands where it is not already present.

A number of thorny thickets of Gmelina elliptica (kalngebard ra belau) were seen on the northern end of Babeldaob and occasional examples are present in most of the Babeldaob states. It is also present on Malakal. It is particularly prevalent in Ngaraard and Ngerchelong States between Chelab and Ollei village. While native to Palau, this species should not be introduced to islands where it is not already present.

Lygodium microphyllum (osuchedechui, Old World climbing fern) is common in taro patches on Peleliu and Babeldaob. While native to Palau it is a weedy species in taro patches and is an introduced weed species in the United States and the West Indies.

Merremia peltata (kebeas, merremia) is quite invasive along forest edges and wherever there has been disturbance, overtopping even mature trees. It is not known whether this species is native or an early introduction to Palau, but it is reported here as a native species. Local people say that there was once less of it, but this may just be because there is now substantially more disturbed area that provides suitable habitat. In any case, whether native or not, it is certainly an aggressive vine, not only in Palau but also on other Pacific islands (on some of which it is known to be introduced).

Operculina turpethum (ongucheta rekung), a native vine common throughout the Pacific, occupies a similar ecological niche as Merremia peltata, and is very prevalent in some locations where the latter species is absent, particularly on Peleliu.

6. Invasive plant species not known to be in Palau

Palau is fortunate that a large number of troublesome species have yet to reach the country. The following list summarizes the worst of these. These species should receive high priority for exclusion from entry into the country and promptly evaluated for eradication if found to be present.

Several Acacia species are invasive on other Pacific islands, notably A. aulacocarpa (brown salwood, brush ironbark wattle, hickory wattle), A. crassicarpa (northern wattle, Papua New Guinea red wattle) and A. curassavica (redwood). A number of other Acacia species are recorded as invasive throughout the world, so caution should be exercised in planting members of this genus. Acacias are often introduced for forestry, wood supply or watershed protection purposes.

Albizia chinensis (Chinese albizia, silktree) is exceptionally widespread in Samoa. Based on its behavior in Samoa, other Pacific islands should be very cautious about introducing this tree.

Ardisia elliptica (shoebutton ardisia) is a problem species in the Cook Islands, Hawai‘i, French Polynesia, Samoa and Florida (US). It produces prolific fruit and crowds out other species in the forest understory. Birds, which eat the fruit, are a major factor in its spread.

Asystasia gangetica subsp. micrantha (Chinese violet, Philippine violet, coromandel) can grow over and smother other vegetation and is a serious invader in Malaysia and Indonesia. Small infestations are being eradicated in northern New South Wales, Australia. It spreads by rhizomes and by seed expelled explosively from capsules and would be a serious weed in Palau. The less invasive subsp. gangetica was seen in cultivation in Koror State and on Babeldaob,

Two rubber trees, Castilla elastica (Panama rubber tree) and Funtumia elastica (African rubber tree), are very invasive in Samoa. Birds spread the seeds of Castilla while those of Funtumia are wind-borne "parachute" seeds.

Cardiospermum grandiflorum (balloon vine; heart seed) is very invasive on Rarotonga, Cook Islands, and is reported to be invasive in Australia as well.

Cecropia obtusifolia (trumpet tree, guarumo) is an invasive tree species that is a problem in Hawai‘i and the Cook Islands (Rarotonga). Cecropia peltata (trumpet tree), a similar species, is invasive in French Polynesia.

Cestrum diurnum (day cestrum, day jessamine, inkberry) and Cestrum nocturnum (night-flowering cestrum) are problem species on a number of Pacific islands. They are species with bird-spread seeds that are often planted as ornamentals.

Clerodendrum chinense (Honolulu rose) is a shade-tolerant species. It primarily reproduces from root suckers and can form dense thickets, crowding out other species. It is a major pest species in Niue, American Samoa and Samoa and is present and invasive on a number of other Pacific islands.

Coccinia grandis (ivy or scarlet gourd) is a smothering vine that is a serious problem on Saipan. The vines climb over trees and form such dense cover that the forest underneath is completely shaded out and destroyed. It is also invasive in Guam and Hawai‘i and is reportedly present in Fiji and Vanuatu. It is a vegetable commonly used in Southeast Asian cooking and the plant is often introduced for that reason. It readily spreads vegetatively through cuttings and, if fruit is present, by birds and probably pigs.

Cordia alliodora (Ecuador laurel, salmwood) was introduced to Samoa, Tonga and Vanuatu as a forestry tree and has proven quite invasive (Tolfts, 1997).

Cryptostegia grandiflora (rubber vine, India rubber vine) is a climbing vine that has become a serious problem in northeastern Queensland, Australia. It is present in New Caledonia and Fiji. A related species, C. madagascariensis, is present in cultivation in Palau but is less of a threat.

Hiptage benghalensis (hiptage) is a problem species in Hawai‘i and is reported to be a very invasive species on La Réunion and Mauritius. It is also becoming invasive in northern Queensland, Australia. The seeds are wind-dispersed and it also can reproduce from cuttings.

Indigofera suffruticosa (indigo) is established on many Pacific islands and is a major weed species in Tonga. It has apparently yet to reach Palau.

Macfadyena unguis-cati (cat’s claw climber) is an aggressive vine that climbs trees and also forms a dense mat on the ground. Control is difficult because it has tuberous roots and reproduces from stem fragments and cuttings. It is a problem species in Hawai‘i and eastern Australia (northern New South Wales and southeast Queensland). It is cultivated as an ornamental in the US, is a problem species on Niue and is reported to be moderately invasive in New Caledonia (Meyer, 2000).

Maesopsis eminii (musizi, umbrella tree) is a large African tree that has been introduced into some countries as a forestry tree. Fruit-eating birds (and possibly fruit bats) spread its seed and it has become a problem in a number of locations. It was introduced as a timber tree to Fiji, where it is starting to naturalize.

Miconia calvescens (the purple plague, velvetleaf) is undoubtedly the most destructive invasive plant in the Pacific. It has been a disaster to the forest ecosystem of Tahiti in French Polynesia and has subsequently spread to other islands in French Polynesia (Meyer and Florence, 1996). It has also escaped in Hawai‘i and is the subject of an intensive and costly eradication effort there. It was discovered in Queensland, Australia, where an eradication project is also under way. This species is an attractive garden plant and might be introduced this way or as tiny seeds on shoes or used equipment.

Other members of the family Melastomataceae (including Arthrostemma ciliatum (everblooming eavender), Heterocentron subtriplinervium (pearl flower), Medinilla magnifica (chandelier tree), Medinilla venosa (holdtight), Melastoma candidum (Asian melastome, Indian rhododendron, Malabar melastome), Melastoma sanguineum (fox-tongued melastoma, red melastome), Memecylon floribundum,, Ossaea marginata, Oxyspora paniculata (bristletips) and Tetrazygia bicolor (Florida clover ash)) that are not native or presently in Palau should also be excluded.

Merremia tuberosa (wood rose), a climbing, smothering vine, is notable for its aggressive behavior on Niue. It is also a problem species in Hawai‘i.

Mucuna pruriens (cow itch, velvet bean) is commonly introduced as a cover crop and for livestock feed. It is a serious problem on Saipan and is considered a weed species in Mexico, Mozambique, Jamaica and Madagascar. While the utilis variety commonly used in agriculture lacks irritating hairs it can apparently revert to type over time.

Odontonema tubaeforme (fire spike, cardinal flower) is a widely cultivated ornamental that is invasive in the understory of moist forests in American Samoa and Samoa. It primarily spreads vegetatively, but over time has managed to cover considerable area in Samoa. A related species, Odontonema cuspidatum, is a problem in Hawai‘i and should also be excluded (some taxonomists consider these the same species).

Passiflora tarminiana [formerly incorrectly known as P. mollissima in Hawai‘i] (banana poka, banana passionfruit), a smothering vine that is a problem in Hawai‘i, is also absent. It can smother the forest canopy when the sub-canopy vegetation is disturbed. Passiflora rubra (red passionfruit) is very invasive in the Cook Islands. Other Passiflora species not already present (Passiflora alata (wingstem passionflower), Passiflora caerulea (blue passionflower), Passiflora coccinea (scarlet passionflower), Passiflora pulchella (two-lobed passionflower), etc.) should also be excluded.

Phyllostachys spp. and other running bamboos are apparently not present in Palau. Phyllostachys and similar bamboo species spread by means of rhizomes, as opposed to bamboos that grow in clumps, and are extremely difficult to control or remove. Phyllostachys nigra (black bamboo) is a problem species in Hawai‘i while P. bissetii is extremely invasive on the island of Mangaia, Cook Islands.

Pimenta dioica (allspice, pimento) is an invasive forest tree. The seeds are bird-dispersed. It is widespread in Tonga (‘Eua), planted in Hawai‘i (where it is naturalizing) and reported to be planted in French Polynesia and Fiji as well. Pimenta racemosa (bay tree), while less of a problem, readily naturalizes as well; for example, in the Cook Islands.

Piper aduncum (spiked pepper) is invasive in Fiji, Papua New Guinea, the Solomon Islands, Indonesia and Malaysia. Its tiny seeds are dispersed by birds and flying foxes and can be introduced into new areas on machinery, particularly logging equipment. Locally, it spreads by suckers, forming large clumps.

Piper auritum (eared pepper, also called "false kava") has been introduced to some Pacific islands as a fast-growing form of kava, but it is worthless in this regard. It is becoming widespread in Tonga and has been the subject of an eradication campaign on the island of Pohnpei, Federated States of Micronesia. It has also been introduced into Hawai‘i but the local kava growers association is working with the authorities to eradicate it there as well. See also SPC Pest Alert No. 19, False Kava. This species suckers profusely and produces many small seeds that can be spread by birds, rodents and bats and can also be introduced into new areas on machinery. It suckers profusely, forming large clumps. Since little kava is grown in Palau, it is unlikely to be introduced deliberately, but with its very small seeds it might be brought in inadvertently.

All Rubus species (raspberries, blackberries, thimbleberries and brambles) should be excluded. These include Rubus alceifolius (giant bramble), invasive in Australia (Queensland) and La Réunion and native to southeast Asia; Rubus moluccanus (Molucca bramble), a serious pest in the Mascarine Islands and native in New Guinea and Rubus rosifolius (roseleaf raspberry, thimbleberry), very invasive in French Polynesia and Hawai‘i and also native to New Guinea. A number of other Rubus species are invasive. In Hawai‘i, R. argutus (prickly Florida blackberry) and R. niveus (hill or Mysore raspberry) are problems. Introduced Rubus species (in particular, R. niveus) are a major problem in the Galapagos Islands. In general, where Rubus species are not present on tropical islands, they should not be introduced. If already introduced, they should be evaluated as candidates for eradication. The vines form thorny thickets and the fruits are widely dispersed by birds.

Schinus terebinthefolius (Christmas-berry, Brazilian pepper) is a major problem species in Hawai‘i was well as Florida (US) and the Indian Ocean islands of La Réunion and Mauritius. The fruits are very attractive to birds, aiding its spread. It is present, though uncommon, in Guam.

Setaria palmifolia (palmgrass, short pitpit) is spectacularly invasive in Samoa, growing in dense, monospecific stands. It is also invasive in Tahiti and Hawai‘i and is on the New Zealand noxious weed list. The seeds are dispersed by wind and possibly by granivorous birds.

Solanum capsicoides (cockroach berry, devil’s apple, soda apple) has been introduced to several South Pacific islands as an ornamental. It is becoming well established in Tonga, particularly on Vava’u. Although small, it is quite spiny and would probably be a problem for agriculture as well as a general nuisance. It produces large amounts of small, tomato-like fruit. Spread may be by birds or pigs or by humans who use the fruit in lei-making.

Solanum mauritianum (bugweed, wild tobacco, tree tobacco) is quite prevalent throughout Tonga and is a noxious weed in South Africa. In Hawai‘i, it is naturalized on slopes and ridges in disturbed wet forest.

Tibouchina herbacea (glorybush, cane ti) is a major problem species in mesic to wet forests in Hawai‘i.

Tribulus cistoides (puncture vine) is a vine with a spiny fruit that is troublesome in coastal habitats in Hawai‘i.

In addition to the grasses mentioned above, a number of other potentially invasive grass species are not yet present in Palau, including Andropogon gayanus, Andropogon glomeratus, Andropogon virginicus, Cenchrus ciliaris, Cortaderia jubata, Cortaderia selloana, Digitaria insularis, Echinochloa polystachya, Hymenachne amplexicaulis, Hyparrhenia rufa, Microlaena stipoides, Paspalum urvillei, Pennisetum clandestinum, Schizachyrium condensatum, Sporobolus elongatus and Tripsacum latifolium. Grasses are easily introduced as contaminants in imported seed, imported sand and gravel or on used machinery, and by their nature tend to be invasive.

The best indicator that a species might be invasive is the fact that it is invasive elsewhere. However, each island ecosystem is unique and invasiveness cannot be predicted with certainty. A good strategy is to be extremely cautious and exclude these and other species known to be invasive or weedy elsewhere (although the best strategy is to exclude all species not shown by risk assessment to be of acceptable risk). Known problem species that have the potential to cause problems in tropical island ecosystems and are not yet present in Palau are listed in Appendix 2, Table 1. These species should be excluded through plant quarantine and, if establishment is detected, promptly evaluated for eradication. Additional species thought to be of low risk or mostly of agricultural concern are listed in Appendix 2, Table 2.

Species that are reported to be present in Hawai‘i, Guam, Yap, Papua New Guinea, the Philippine Islands, Japan and Taiwan, but are not present in Palau are listed in Appendix 3. These species would be of high risk of introduction from air and ship traffic between these points and Palau.

Invasive plants associated with the Compact Road

The U.S. Corps of Engineers, the Office of Environmental Response and Coordination and the Bureau of Agriculture closely monitored activities during the construction of the Compact Road, particularly the introduction of rock and gravel from off-island sources and the hydroseeding of cuts and fills. The following summarizes the invasive plant species found and the actions taken (information furnished by Dr. Joel Miles, National Invasive Species Coordinator, Bureau of Agriculture):

Macroptilium atropurpureum (siratro) was intentionally introduced as a component of hydroseeding. Use was halted soon after the initial hydroseeding due to concerns about potential invasiveness. Siratro has spread to some extent. It has been detected along the access road to the Ngardok Lake Reserve within the Reserve boundary.

Macroptilium lathyroides (phasey bean) was an unintentional introduction, probably as a contaminant of the siratro, since it has been found associated with the siratro seeding.

Ipomoea hederifolia (ivy-leaf morning glory) was an unintentional introduction, probably as a contaminant in the hydroseed seed mix. It was found in only 2 or 3 locations and has apparently been eradicated.

Praxelis clematidea (praxelis) was also an unintentional introduction, probably as a contaminant in the hydroseed seed mix. It was found in only one location, in 2007, apparently present for one or two years. All the plants were killed with herbicide, but they had produced seed, so the site of the infestation is being monitored for possible regrowth.

Indigofera hirsuta (hairy indigo) was an unintentional introduction, probably as a contaminant of the hydroseed seed mix. It was found along one section of road in 2007. This section was newly seeded and the plants were discovered before they had set seed. All of them were uprooted and burned and none have been found since. The Compact Road is regularly monitored for regrowth of this plant.

In summary, good contract specifications, close monitoring and continued vigilance have paid off in a minimum number of new introductions, most of which were caught and eradicated before they could spread.

General observations and recommendations

Palau has taken a number of steps to actively prevent the introduction of invasive plant species and manage or eradicate those that have become established. The Bureau of Agriculture has operational responsibility and there is a National Invasive Species Coordinator, located at the Bureau, who provides oversight and coordination. The Quarantine Service works to prevent new introductions while the Division of Forestry’s Invasive Weed Eradication Officer and assistant provide a focal point for management of new and established species.

Palau has an Invasive Weeds Committee (Weedbusters), but the committee has not been active recently. Close and immediate coordination and cooperation between various government departments and other entities is essential when an invasive species problem is encountered, especially when there is a need to move quickly to eradicate an introduced species. Such a committee can be effective both for long-term strategic actions, such as review and strengthening of relevant laws and regulations, as well as short-term tactical and operational problems, such as action when a new species is found to have been introduced. The National Government and the Forestry Department have invasive species action plans. These plans should be reviewed and updated, if necessary, with the aid of the information provided in this report. These plans could be complemented by one or more site based plans, such as for the Rock Islands, newly designated areas in Palau’s recently formed Protected Areas Network, such as Lake Ngardok, or within the scope of newly forming watershed partnerships (Babeldaob Watershed Alliance). These plans would include critical areas to be protected and species subject to control or eradication as well as the role of each governmental agency or other entity in control or eradication measures. Time, money and people are always in limited supply and must be directed to the places where they will do the most good. Economic analysis can be used to assess the costs and benefits of management strategies and prioritize action. Some recommendations are made below as to possible actions against individual plant species, but these should be tested against available resources and other priorities.

Palau has laws and regulations in place that deal with quarantine and new introductions and in 2008 passed the Protected Areas Network Act to protect biodiversity. However, there are at present no laws or regulations to control movement between islands within Palau. Quarantine has worked informally with the Southwest Island states of Hatohobei and Sonsorol to inspect cargo prior to departure to these islands, but there is no formal agreement for this. The first line of defense against invasive species, and the most cost-effective, is to keep them out. Control at ports of entry is essential, and ecosystem managers should continue to work closely with plant protection and quarantine officials to combat known and potential invasive plant species. Plant quarantine officers can benefit from receiving training in identification of both agricultural pests and those that threaten wildland ecosystems. The PIER web site and CD can be used as reference tools when unknown or suspicious plants are encountered. At a minimum, a list of known noxious species to be excluded should be developed and exclusion of these species should be backed by the force of law and regulation. The Department of Agriculture should continue to use available Weed Risk Assessment (WRA) tools (Hawaii-Pacific and Australia, or possibly others) to screen potential imports. The cost is relatively small and could be passed on to importers as a fee or funded in some other manner. Weed risk assessments can be used along with a "white list" approach where only species shown to be non-invasive are allowed entry, essentially excluding all alien species not shown to be of acceptable risk. The Secretariat of the Pacific Community has a Plant Protection Training Officer for Micronesia who provides assistance to strengthen quarantine operations.

In the case of new introductions, the ability to take prompt action is essential, as expanding infestations soon become uneconomical to control. Regular monitoring programs for early detection and rapid response procedures, together with emergency funding mechanisms, should be in place.

Although few in number, local nurseries, botanical gardens and plant importers can be important sources of new introductions. A positive approach is to work together to develop a list of native and non-invasive species that the public can be encouraged to plant. Likewise, state, village and local groups can perform an important education function for their members in what species to avoid and can assist in "weed-spotting" and controlling infestations of invasive plants. Demonstrated leadership by government agencies, including prohibiting the use of invasives species in public projects and promoting the use of non-invasive and native species, sets an example for others to follow.

Mapping and monitoring are important actions to incorporate into the program. Foresters, conservation officers, extension agents and others that spend time in the field should be alert to new species that exhibit invasive behavior and report their locations. Periodically scheduled surveys should also be conducted for new or expanding infestations, particularly along the Compact Road. Most pest species are deliberately or inadvertently introduced by people and tend to first become established on farms or in gardens and disturbed areas, such as roadsides. The "War on Weeds" hotlines should continue to be publicized to encourage the prompt reporting of suspicious species. Areas previously used for agricultural and forestry species trials as well as other areas where exotic species have been planted should continue to be monitored for the spread of exotic species. Palau should also utilize the results of the Spatial Analysis Program, and similar programs, to help identify areas at high risk of introductions and focus areas where treatment of established invasives is a high priority.

Laws and regulations should be reviewed to make sure they are adequate to deal with new introductions. The Bureau of Agriculture now has the authority to require the control of noxious species on private or customary lands or to take action on private lands if the landowner cannot be located or does not take prompt action. If needed, model laws and regulations can be obtained from states and countries that have implemented them.

In addition to routine screening of people and cargo at airports and ports, the Quarantine Service should insure that other pathways are effectively blocked. Steam cleaning or power washing of all used cars, trucks and equipment coming into Palau should be required and enforced to protect against invasive plants, insects and diseases. Especially problematic are roadbuilding machinery, military equipment and off-road vehicles. The planned US military buildup on Guam is likely to bring more invasive species into Guam and surrounding nations, either directly via incoming troops and equipment during training, or indirectly, via the movement of people and goods from Guam. Quarantine inspectors should be especially vigilant to make sure used cars, trucks and equipment from Guam, Hawai‘i, Southeast Asia, Indonesia, New Guinea, Australia and the Philippines are clean as many dangerous weeds are present in these locations. Likewise, importation of sand, gravel, seed and other easily contaminated material from outside the country should be subject to restriction, inspection and post-release monitoring. Several examples of invasive species moved about with gravel and soil were seen during both the 2002 and 2008 surveys as well as contamination of the seed used in the stabilization seeding on the Compact Road. Most imported seed will not be 100% free of contamination and the resultant plantings must be monitored for the establishment of weed species.

Quarantine inspectors should closely inspect boots, camping equipment and other material for soil and seeds, particularly when they have been used in countries where Miconia calvescens and other small-seeded species are present. It would be desirable to have a question on the customs/quarantine declaration form that asks visitors if they have boots or camping equipment or have been in forests as well as farms (as is done in Australia and New Zealand).

An evaluation should be conducted for any new species that appears to be invasive or is known to be invasive elsewhere. The Institute of Pacific Islands Forestry and the University of Hawai‘i Department of Botany adapted the Australian risk assessment system to the needs of the Pacific. This system is available to Palau, either through use of the assessments already completed and posted at http://www.botany.hawaii.edu/faculty/daehler/wra/ or on the PIER web site (http://www.hear.org/pier/wra.htm) or by requesting assessments of new or suspicious species by sending relevant information through the USFS’s Forest Health Coordinator in Hawaii. Similarly, technical assistance on recommended control methods should be requested through the USFS, SPC or the Pacific Invasives Learning Network, if needed. Assistance is available on-line from experts through the Pacific Pestnet list-server, and Palau should continue to take advantage of this service.

The successful education program dealing with the risks and consequences of introductions and the benefit of using native species should continue. Encourage responsible actions such as following quarantine regulations, not dumping garden cuttings in the woods and reporting suspicious plants. Public service announcements on television or radio, "wanted" posters, and especially educating school-aged children, are important outreach tools. Prompt follow-up to public reports and inquiries is essential to maintain the credibility of a public education program. The weed "hot lines" telephone numbers, the visibility and involvement of the Bureau of Agriculture invasive species officers, the "War on Weeds" campaign and the public clean-up days are good examples of public information and involvement.

The public also needs to understand that the immediate eradication of a problem species, even if it involves the use of pesticides, may be better than living with a problem species forever. Fortunately, the public has been very supportive of the eradication actions taken so far. A good job appears to have been done in informing and involving the public in proposed control and eradication actions. Personal contact and the ability to provide a substitute plant to replace an invasive one can often persuade landowners to permit the eradication of troublesome species.

Palau has set aside areas to be maintained in natural condition as a heritage for future generations, for the protection of native biodiversity and tourism values and as examples of Palau’s original forest cover. Protection of these areas will involve a continuous and long-term effort to exclude invading species. Fortunately, Palau’s natural ecosystems seem to be rather robust in resisting invading plants, compared to most Pacific islands, but they are not immune and some present and potential invaders could pose a serious threat. Keeping out shade-tolerant species that can invade closed forests is the biggest problem. Intact native forests are the most resistant to invasion and any measures that limit the amount of disturbance will help keep invasive species out. Prompt detection and eradication of new introductions and appropriate control of existing invaders will be necessary to maintain natural and protected areas in the desired condition.

Palau is encouraged to continue to take advantage of financial and technical assistance available to deal with invasive plant species. Cost-share funding can be requested from the US Forest Service to provide locally available expertise in forest health protection and deal with specific forest health problems, including invasive plants, under the Cooperative Forestry and Hawai‘i Tropical Forestry Recovery Acts. In addition to cost-share funding, experts are also on call from the Forest Service’s Forest Health Protection staff and the Pacific Invasives Learning Network, or they can arrange for expert consultations from PILN members.

Species-specific recommendations

The purpose of this survey was to give an overall assessment of the situation. In the short time available it was not possible to perform the evaluations that would be needed to justify control or eradication programs for individual species. For many species, therefore, our recommendations are provisional and must be subject to a more complete evaluation as to extent, invasiveness and the feasibility of control or eradication. Technical assistance should be requested, if needed, to evaluate individual species.

Table A. Priority species for exclusion from Palau

Scientific Name

Common Names (abridged)

Family

Invasive in:

Acacia aulacocarpa brown salwood Fabaceae Cook Islands
Acacia crassicarpa redwood Fabaceae Cook Islands
Acacia glauca northern wattle, Papua New Guinea red wattle Fabaceae Cook Islands
Albizia chinensis Chinese albizia, silktree Fabaceae Samoa
Ardisia elliptica shoebutton ardisia Myrsinaceae Cook Islands, French Polynesia, Hawai‘i, Samoa and USA (Florida)
Cardiospermum grandiflorum balloon vine; heart seed Sapindaceae Cook Islands (Rarotonga)
Castilla elastica Panama rubber tree Moraceae Samoa
Cecropia obtusifolia trumpet tree, guarumo Cecropiaceae Hawai‘i, Cook Islands
Cecropia peltata trumpet tree Cecropiaceae French Polynesia
Cestrum diurnum day cestrum Solanaceae Cook Islands
Cestrum nocturnum night-flowering cestrum Solanaceae Cook Islands, French Polynesia (Tahiti), Hawai‘i, Samoa, Tonga
Clerodendrum chinense Honolulu rose Lamiaceae Samoa, Tonga and elsewhere
Coccinia grandis ivy gourd, scarlet-fruited gourd Cucurbitaceae Hawai‘i, Saipan
Cordia alliodora Ecuador laurel, salmwood Boraginaceae Samoa, Tonga, Vanuatu
Cryptostegia grandiflora rubber vine, India rubber vine Asclepiadaceae Australia (Queensland)
Eugenia uniflora Surinam cherry Myrtaceae Cook Islands
Funtumia elastica African rubber tree Apocynaceae Samoa
Hiptage benghalensis hiptage Malpighiaceae Hawai‘i, La Réunion, Mauritius, Australia (Queensland)
Indigofera suffruticosa indigo Fabaceae Tonga and elsewhere
Macfadyena unguis-cati cat’s-claw climber Bignoniaceae Hawai‘i, Niue, New Caledonia
Maesopsis eminii umbrella tree, musizi Rhamnaceae Fiji
Merremia tuberosa wood rose Convolvulaceae Hawai‘i, Niue
Miconia calvescens miconia, velvetleaf, purple plague, bush currant Melastomataceae French Polynesia, Hawai‘i
Mucuna pruriens cow itch, velvet bean Fabaceae Saipan
Odontonema tubaeforme fire spike, cardinal flower Acanthaceae American Samoa, Samoa; Hawai‘i (Odontonema cuspidatum)
Passiflora tarminiana banana poka, banana passionfruit, bananadilla Passifloraceae Hawai‘i
Passiflora spp. all other Passifloraceae not already present Passifloraceae
Phyllostachys spp. running bamboos Poaceae Hawai‘i (P. nigra), Cook Islands (P. bissetii)
Pimenta dioica pimento, allspice Myrtaceae Hawai‘i, Tonga
Pimenta racemosa bay tree Myrtaceae Cook Islands
Piper aduncum spiked pepper Piperaceae Fiji, Papua New Guinea, Solomon Islands, Indonesia, Malaysia
Piper auritum eared pepper, false kava Piperaceae Hawai‘i, Pohnpei, Tonga
Rubus spp. raspberries, blackberries, brambles Rosaceae Hawai‘i, French Polynesia, etc.
Schinus terebinthifolius Christmas-berry, Brazilian pepper Anacardiaceae USA (Hawai‘i, Florida)
Setaria palmifolia palmgrass, short pitpit Poaceae Hawai‘i, French Polynesia (Tahiti), Samoa
Solanum capsicoides cockroach berry, devil’s apple, soda apple Solanaceae Hawai‘i, Samoa, Tonga
Solanum mauritianum bugweed, wild tobacco, tree tobacco Solanaceae Hawai‘i, Tonga
Tibouchina herbacea glorybush, cane ti, tibouchina Melastomataceae Hawai‘i
Tribulus cistoides puncture vine Zygophyllaceae Hawai‘i
All grasses all other grass species not already present Poaceae pan-tropical
All melastomes all other non-native melastomes Melastomataceae Hawai‘i, etc.

Note: Appendix 2, Table 1 is a complete list of invasive and potentially invasive species of environmental concern
not yet present in Palau. Appendix 2, Table 2 contains a list of other invasive species not reported to be present in Palau.


Table B. Cultivated species of possible threat to Palau

Scientific Name

Common Names (abridged)

Family

Present on:

Invasive in:

Acacia farnesiana Ellington curse, klu Fabaceae Babeldaob Fiji, French Polynesia, New Caledonia, Solomon Islands, Vanuatu
Alternanthera ficoidea [=A. tenella] ‘Bettzickiana’ sanguinarea Amaranthaceae Babeldaob GRIN says "naturalized elsewhere"
Asparagus densiflorus asparagus fern, sprengeri fern, smilax, regal fern Liliaceae Koror, Ngerkebesang Hawai‘i
Barleria lupulina hophead Philippine violet Acanthaceae Babeldaob, Peleliu Mauritius, Timor, Queensland
Calathea majestica no common name Marantaceae Koror
Calotropis gigantea calotrope, crown flower, madar Ascelepiadaceae Koror, Ngerkebesang, Babeldaob, Peleliu Australia (Northern Territory, northwest Western Australia), Timor
Calliandra calothyrsus powderpuff, red calliandra Fabaceae Babeldaob Indonesia
Calliandra surinamensis pink powder puff Fabaceae Koror Fiji
Costus woodsonii indian-head ginger, red cane Costaceae Ngerkebesang Hawai‘i
Cinnamomum verum ochod ra ngebard, cinnamon tree Lauraceae reported present, not found American Samoa, Cook Islands, Samoa
Cyperus involucratus umbrella sedge Cyperaceae Koror Cook Islands, Tonga
Eichhornia crassipes bung el ralm, water hyacinth Pontederiaceae Koror, Ngerkebesang, Babeldaob pantropical
Elaeocarpus angustifolius blue fig, blue marble tree Elaeocarpaceae reported present, not found Samoa
Episcia reptans flame violet Gesneriaceae Koror, Ngerkebesang
Eugenia uniflora Surinam cherry Myrtaceae Koror Cook Islands
Flemingia macrophylla Fabaceae Koror, Babeldaob Cook Islands, Samoa
Hevea brasiliensis Brazilian rubber tree Euphorbiaceae reported present on Koror and Babeldaob but not found Christmas Island (Indian Ocean)
Livistonia chinensis Chinese fan palm, fountain palm Arecaceae Koror Florida (US) and Hawai‘i
Murraya paniculata orange jessamine, satin-wood, Chinese box Rutaceae Koror, Ngerkebesang, Babeldaob French Polynesia, Hawai‘i; host to citrus psyllid
Nymphaea spp. waterlily Nymphaeaceae Koror pantropical
Pennisetum setaceum fountain grass Poaceae Ngerkebesang, Babeldaob USA (California, Hawai‘i), Canary Islands
Pereskia aculeata Barbados gooseberry, leafy cactus Cactaceae Ngercheu (Carp) Australia, South Africa
Pistia stratiotes duckweed, water lettuce Araceae Babeldaob Worldwide tropics
Pithecellobium dulce kamatsíri, Madras thorn Fabaceae Babeldaob Hawai‘i, Guam
Quisqualis indica Rangoon creeper Combretaceae Ngerkebesang, Babeldaob Australia (Northern Territory)
Sanchezia parvibracteata sanchezia Acanthaceae Koror, Malakal, Ngerkebesang Hawai‘i
Senna siamea cassod tree, Siamese cassia Fabaceae Babeldaob Australia, French Polynesia (Tahiti)
Senna surattensis scrambled eggs Fabaceae Babeldaob Hawai‘i
Sesbania grandiflora katurai, sesbania, scarlet wisteria Fabaceae Koror, Malakal, Babeldaob American Samoa, Samoa
Spathodea campanulata orsachel kui, African tulip tree Bignoniaceae Koror, Ngerkebesang, Babeldaob Fiji, French Polynesia, Hawai’i, Samoa, Vanuatu
Stapelia gigantea carrion flower, giant toad plant Asclepiadaceae Babeldaob Hawai‘i
Syzygium cumini mesekerrák, Java plum Myrtaceae Koror, Babeldaob, Aulupse‘el Cook Islands, Hawai‘i, French Polynesia (Raiatea)
Syzygium jambos malabar plum, Malay apple Myrtaceae Koror, Babeldaob French Polynesia, Galapagos Islands, Mauritius, La Réunion
Tabebuia heterophylla pink tecoma, pink trumpet tree, white cedar Bignoniaceae Koror, Malakal, Ngerkebesang Hawai‘i
Vitex parviflora small-leaved vitex Verbenaceae reported present in Malakal (Toirechuil) Guam

Note: Cultivated plants with invasive potential are noted in Tables 2, 3 and 4, Appendix 1.


Table C. Critical species that should be subject to inter-island quarantine

Scientific Name

Common name

Present on:

Acacia farnesiana Ellington curse, klu, sweet acacia Babeldaob
Adenanthera pavonina telengtúngd, telentundalel, coral bean tree Koror, Malakal, Ngerkebesang, Babeldaob
Allamanda cathartica allamanda, yellow trumpet vine Koror, Malakal, Ngerkebesang, Babeldaob
Alternanthera brasiliana Brazilian joyweed, Joseph’s coat Koror, Malakal, Ngercheu (Carp Resort)
Antigonon leptopus dilngau, chain of love Koror, Babeldaob
Arundo donax giant reed Koror, Babeldaob
Asparagus densiflorus asparagus fern, sprengeri fern Koror, Ngerkebesang
Barleria lupulina hophead Philippine violet Babeldaob, Peleliu
Calathea majestica no common name Koror
Calotropis gigantea calotrope, crown flower, madar Koror, Ngerkebesang, Babeldaob, Peleliu
Calliandra calothyrsus powderpuff, red calliandra Babeldaob
Chromolaena odorata ngesngesil, chromolaena, Siam weed Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu, Ngidech
Chloris virgata feather finger grass, feathery Rhodes grass Babeldaob
Cinnamomum verum ochod ra ngebard, cinnamon tree Not known
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Kayangel, Peleliu, Ngercheu (Carp Resort)
Clidemia hirta kúi, Koster’s curse Malakal, Babeldaob
Costus woodsonii indian-head ginger, red cane Ngerkebesang
Crotalaria retusa devill-bean, rattlepod Peleliu, perhaps Babeldaob or Koror
Cyperus involucratus deus, umbrella sedge Koror
Dieffenbachia seguine spotted dieffenbachia, dumb cane Koror, Malakal, Ngerkebesang, Babeldaob, Peleliu
Dissotis rotundifolia dissotis, pink lady Koror, Babeldaob
Eichhornia crassipes bung el ralm, water hyacinth Koror, Ngerkebesang, Babeldaob
Elaeocarpus angustifolius blue fig, blue marble tree Not known
Epipremnum pinnatum ‘Aureum’ pothos, money plant Koror, Malakal, Ngerkebesang, Babeldaob
Episcia reptans flame violet Koror, Ngerkebesang
Falcataria moluccana ukall ra ngebard, Moluccca albizia Koror, Babeldaob
Flemingia macrophylla no common name Koror, Babeldaob
Hedychium coronarium white ginger Koror, Ngerkebesang
Hevea brasiliensis Brazilian rubber tree, Para rubber tree Koror, Babeldaob
Hyptis capitata knobweed Koror, Malakal, Ngerkebesang, Babeldaob
Hyptis pectinata mint weed Babeldaob, Angaur?
Imperata cylindrica kasoring, blady grass, cogon grass Babeldaob, Ngerkebesang?, Angaur?
Ipomoea hederifolia ivy-leaf morning glory, star ipomoea Babeldaob
Ipomoea quamoclit asangao, star of Bethlehem, cypress vine Koror, Babeldaob
Lantana camara lantana Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu, Ngercheu (Carp Resort)
Leucaena leucocephala telengtungd, leucaena Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu, Ngercheu (Carp Resort), Ngerchong, Sonsorol
Macroptilium lathyroides cow pea, phasey bean Babeldaob
Melaleuca quinquenervia cajeput, paper bark tree Babeldaob
Melia azedarach Chinaberry, pride-of-India, Indian lilac Koror, Babeldaob
Melinis minutiflora molasses grass Babeldaob
Merremia peltata kebeas, merremia Koror, Malakal, Ngerkebesang, Babeldaob, Kayangel
Mikania micrantha teb el yas, mile-a-minute weed Koror, Malakal, Ngerkebesang, Babeldaob, Peleliu
Mimosa diplotricha mechiuaiuu, giant sensitive plant Koror, Malakal, Ngerkebesang, Babeldaob, Angaur
Mimosa pudica mechiuaiuu, sensitive plant Koror, Malakal, Ngerkebesang, Babeldaob, Angaur
Panicum maximum Guinea grass Koror, Babeldaob
Pennisetum polystachion desum, mission grass Koror, Malakal, Ngerkebesang, Babeldaob, Peleliu
Pennisetum setaceum fountain grass Ngerkebesang, Babeldaob
Pereskia aculeata Barbados gooseberry, leafy cactus Ngercheu (Carp)
Pluchea carolinensis sour bush Peleliu
Psidium cattleianum strawberry guava Koror?
Psidium guajava guabang, kuabang, guava Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu, Bkul a Chesemiich, Ngerchong
Senna siamea cassod tree Siamese cassia Babeldaob
Sesbania cannabina prickly sesban Babeldaob, Koror, Malakal
Sesbania grandiflora katurai, hummingbird tree, scarlet wisteria tree Koror, Malakal, Babeldaob
Solanum torvum prickly solanum, devil’s fig Babeldaob
Spagneticola trilobata ngesil ra ngebard, Singapore daisy Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu
Stachytarpheta cayennensis louch beluu, blue rat’s tail, dark blue snakeweed Koror, Malakal, , Babeldaob, Angaur, Kayangel, Peleliu, Ngidech, Urukthapel
Syngonium angustatum arrowhead plant, goosefoot plant Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu
Tephrosia candida white tephrosia Babeldaob
Thunbergia grandiflora bung el etiu, blue trumpet vine, Bengal trumpet Koror, Babeldaob, Kayangel
Timonius timon liberal Ngerkebesang, Angaur, Peleliu, Kayangel, Bkul a Chesemiich, Ngercheu (Carp Resort), Ngerchong, Ngchelobel, Ngeanges
Turnera ulmifolia/subulata yellow alder, sage rose/white alder Koror, Malakal, Ngerkebesang, Babeldaob, Angaur, Peleliu
Vitex parviflora small-leaved vitex Malakal (Toirechuil)

Note: This table lists only the most serious invasive plants of environmental concern. See Appendix 6 and
Appendix 7 for complete lists of species not yet present on each island or island group.


Table D. Summary of major invasive species present in Palau with recommendations for their management

Scientific Name

Common Names (abridged)

Family

Comments and recommendations

* Acacia farnesiana Ellington curse, klu, sweet acacia Fabaceae Eradicate if still present.
Adenanthera pavonina telengtúngd, telentundalel, coral bean tree Fabaceae Assess extent and rate of spread, control as appropriate in sensitive and natural areas.
Aeschynomene americana American joint vetch Fabaceae Map extent of infestation, determine if control or eradication is needed.
Allamanda cathartica allamanda, yellow trumpet vine Apocynaceae Discourage planting; remove when a problem.
Alternanthera brasiliana Brazilian joyweed, Joseph’s coat Amaranthaceae Discontinue planting; be alert to escapes from cultivation; eradicate single plant on Ngercheu Island (Carp Resort) and other isolated plantings.
Alternanthera ficoidea [=A. tenella] ‘Bettzickiana’ sanguinarea Amaranthaceae Evaluate for invasiveness (request or conduct risk assessment).
Antigonon leptopus dilngau, chain of love Polygonaceae Discourage further planting; map current distribution and work to eradicate over time.
Arundo donax giant reed Poaceae Map infestations; limit burning and monitor for spread after wildfires; control as needed in sensitive and natural areas.
* Asparagus densiflorus asparagus fern, sprengeri fern Liliaceae Eradicate this and other ornamental Asparagus species.
Barleria lupulina hophead, Philippine violet Acanthaceae Eradicate if of limited extent.
Bryophyllum pinnatum life plant Crassulaceae Control outside of cultivation.
Bryophyllum delagoense chandelier plant Crassulaceae Control outside of cultivation.
* Calamus sp. rattan, bangerenguis ra ngebard Arecaceae Map distribution; evaluate and possibly propose for eradication.
Calathea majestica [=C. princeps] no common name Marantaceae Monitor for possible spread and to determine if control or eradication is needed.
Calotropis gigantea calotrope, crown flower, madar Ascelepiadaceae Monitor for spread.
Calliandra calothyrsus powderpuff, red calliandra Fabaceae Discourage further planting; eradicate if of limited extent.
Calliandra surinamensis pink powder puff Fabaceae Discourage further planting; eradicate if of limited extent.
Casuarina equisetifolia ngas, casuarina, ironwood, Australian pine Casuarinaceae Eradicate on Tobi and Helen’s Reef; exclude from Sonsorol and other islands of Sonsorol State; consider replacement with more suitable species on Rock Island beaches.
Chloris virgata feather finger grass, feathery Rhodes grass Poaceae Map extent of infestation and evaluate whether control or eradication is needed.
Chromolaena odorata ngesngesil, chromolaena, Siam weed Asteraceae Introduce new biological control agents if practical and maintain existing ones; extirpate on Ngidech Island and any other isolated areas in the Rock Islands.
Chrysopogon aciculatus iul, Mackie’s pest, lovegrass Poaceae Provide advice on control to Sonsorol and Tobi; promptly eradicate if found on new islands.
Cinnamomum verum ochod ra ngebard, cinnamon tree Lauraceae Eradicate if found and of limited extent.
* Cleome viscosa tickweed, spider flower Capparaceae Eliminate at the locations where found.
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Lamiaceae Discourage planting and dumping of cuttings; assist landowners in control; control outside of cultivation; evaluate for possible eradication on Peleliu and Angaur.
* Clidemia hirta kúi, Koster’s curse Melastomataceae Check status of previously introduced biocontrol agents. Map distribution of main infestation, especially downstream. Evaluate extent and the possibility of additional biological controls; follow recommendations in 2006 biological evaluation. .
*† Costus woodsonii indian-head ginger, red cane Costaceae Discourage further planting; eradicate if of limited extent.
*† Crotalaria retusa devil-bean, rattlepod Fabaceae Eradicate from Peleliu (planted specimens); search for source of seed and eradicate if feasible.
* Cyperus involucratus deus, umbrella sedge Cyperaceae Discourage further planting; eradicate if of limited extent.
*† Datura metel jimson weed Solanaceae Eradicate this species from Ngercheu (Carp) Island; eliminate other examples if and when found.
Dieffenbachia seguine spotted dieffenbachia, dumb cane Araceae Discourage planting and dumping of cuttings; control outside of cultivation, particularly in moist areas.
Dissotis rotundifolia dissotis, pink lady Melastomataceae Discourage planting and dumping of garden waste; control escaped populations as needed.
Eichhornia crassipes bung el ralm, water hyacinth Pontederiaceae Eradicate if of limited extent.
Elaeocarpus angustifolius blue fig, blue marble tree Elaeocarpaceae Try to locate; evaluate for invasiveness or eradicate if found and of limited extent.
Epipremnum pinnatum ‘Aureum’ pothos, money plant Araceae Control outside of cultivation, especially when growing in forested areas.
Episcia reptans flame violet Gesneriaceae Request or conduct a risk assessment to determine further management action.
Erechtites hieraciifolius fireweed Asteraceae Determine extent of infestation; evaluate for eradication.
Eugenia uniflora Surinam cherry Myrtaceae Eradicate
Falcataria moluccana ukall ra ngebard, Moluccca albizia Fabaceae Map current distribution; evaluate reproduction and spread (request technical assistance as needed); discourage further planting; control in sensitive and natural areas as needed
Flemingia macrophylla no common name Fabaceae Discontinue planting, control outside of cultivation; eradicate if possible.
Gmelina elliptica kalngebard ra belau Lamiaceae Do not introduce to new islands.
* Hamelia patens firebush, redhead, scarletbush Rubiaceae Discourage further planting; evaluate for eradication.
Hedychium coronarium white ginger Zingiberaceae Control outside of cultivation.
Hemigraphis alternata metal leaf, red ivy Acanthaceae Control outside of cultivation.
Hevea brasiliensis Brazilian rubber tree, Para rubber tree Euphorbiaceae Try to locate; evaluate for invasiveness or eradicate if of limited extent.
Hyptis capitata knobweed Verbenaceae Exclude from islands where it does not occur and promptly eradicate if found on new islands.
* Hyptis pectinata mint weed Verbenaceae Evaluate extent and eradicate if possible.
* Imperata cylindrica kasoring, blady grass, cogon grass Poaceae Continue eradication program; survey periodically for additional sites.
* Inga edulis ice cream bean Fabaceae Monitor for reproduction and additional specimens.
* Ipomoea hederifolia ivy-leaf morning glory, star ipomoea Convolvulaceae Monitor for additional infestations, eradicate if found.
Ipomoea quamoclit asangao, star of Bethlehem, Cupid’s flower, cypress vine Convolvulaceae Eradicate if of limited extent.
Lantana camara lantana Verbenaceae Check status of previously introduced biocontrol agents, reintroduce or introduce new ones as appropriate; monitor for spread to Rock Islands and destroy any plants found there.
Livistonia chinensis Chinese fan palm, fountain palm Arecaceae Map and monitor for spread.
Melaleuca quinquenervia cajeput, paper bark tree Myrtaceae Survey for extent and reproduction; consider control measures to limit spread, particularly in moist areas.
Melampodium divaricatum blackfoot, golden button Asteraceae Evaluate potential for naturalization and spread (conduct or request a risk assessment). Evaluate for eradication if of high risk.
* Melia azedarach Chinaberry, pride-of-India, Indian lilac Meliaceae Trace source(s) of distribution, discourage further planting, eradicate existing specimens.
Melinis minutiflora molasses grass Poaceae Map extent of infestation(s), especially along roadsides and evaluate for further action; at a minimum, monitor for spread, especially if burned; limit burning.
* Merremia hederacea ivy woodrose Convolvulaceae Eradicate infestation in Koror.
Merremia peltata kebeas, merremia Convolvulaceae Exclude from islands where not present; provide advice to landowners on control.
* Mikania micrantha teb el yas, mile-a-minute weed Asteraceae Evaluate eradication program to determine feasibility of continuing or of alternative actions.
Mimosa diplotricha mechiuaiuu, giant sensitive plant Fabaceae Check status of previously introduced biocontrol agents, reintroduce or introduce new ones as appropriate; exclude from islands where not present; eradicate on islands with small populations; promptly eradicate if found on new islands.
Mimosa pudica mechiuaiuu, sensitive plant Fabaceae Exclude from Peleliu and other islands where not present, eradicate promptly if found on these islands.
Murraya paniculata orange jessamine, satin-wood, Chinese box Rutaceae Reduce the number of plants to prevent spread of the citrus psyllid if it should be introduced.
Panicum maximum Guinea grass Poaceae Determine distribution; limit burning.
Pennisetum polystachion desum, mission grass Poaceae Work to decrease burning and other disturbance.
* Pennisetum setaceum fountain grass Poaceae Trace source(s) of distribution, map and eradicate if feasible.
*† Pereskia aculeata Barbados gooseberry, leafy cactus Cactaceae Eradicate on Ngercheu (Carp) Island and if found elsewhere.
* Pistia stratiotes duckweed, water lettuce Araceae Locate source; eradicate if possible.
Pithecellobium dulce kamatsíri, opiuma, Madras thorn Fabaceae Locate any additional specimens; monitor for invasiveness; eradicate if of limited extent.
Pluchea carolinensis sour bush Asteraceae Consider eradication (low priority) to prevent spread to additional islands
Pluchea indica Indian fleabane, Indian pluchea, Indian camphorweed Asteraceae Consider eradication (low priority) to prevent spread to additional islands
Pseuderanthemum carruthersii Acanthaceae Discourage further planting; control outside of cultivation; eradicate on Sonsorol.
* Psidium cattleianum strawberry guava Myrtaceae Attempt to locate previously reported specimen(s) and eradicate if found.
Psidium guajava guabang, kuabang, guava Myrtaceae Control as needed if found in sensitive and natural areas.
Quisqualis indica Rangoon creeper Combretaceae Monitor for invasiveness.
Ricinus communis gelug, maskerekur, uluchula skoki, castor bean Euphorbiaceae Monitor spread; work to reduce existing populations.
Schefflera actinophylla octopus tree Araliaceae Eradicated; monitor for reintroduction.
Senna siamea cassod tree Siamese cassia Fabaceae Map distribution. Discourage further planting; eradicate if of limited extent.
Senna surratensis scrambled eggs Fabaceae Map distribution. Discourage further planting; eradicate if of limited extent.
Sesbania grandiflora katurai, hummingbird tree, scarlet wisteria tree Fabaceae Discourage further planting; monitor closely for any spread; eradicate if it begins to spread.
* Solanum torvum prickly solanum, devil’s fig Solanaceae Evaluate for extent; kill plants when found; encourage and assist landowners to control plants on their land; eradicate if of limited extent.
* Spathodea campanulata orsachel kui, African tulip tree Bignoniaceae Eliminate remaining infestation; monitor for reintroduction.
Sphagneticola [=Wedelia] trilobata ngesil ra ngebard, Singapore daisy Asteraceae Discourage further planting; local control as needed; exclude from islands where not present and promptly eradicate if found on them.
* Striga asiatica Asiatic witchweed Scrophulariaceae Map extent of infestation and evaluate for possible eradication.
Syngonium angustatum arrowhead plant, goosefoot plant Araceae Control outside of cultivation, especially when growing in forested areas.
Syzygium cumini mesekerrák, Java plum Myrtaceae Try to locate, evaluate for invasiveness and possible eradication.
Tecoma stans yellow bells, yellow-elder, yellow trumpetbush Bignoniaceae Monitor for spread; eradicate on Sonsorol.
Tephrosia candida white tephrosia Fabaceae Try to locate, evaluate for invasiveness and possible eradication.
* Thunbergia grandiflora bung el etiu, blue trumpet vine, Bengal trumpet Acanthaceae Discourage planting; control as needed; eliminate plants outside of cultivation; eradicate in Melekeok and Aimeliik/Ngatpang; evaluate for eventual eradication.
Timonius timon Liberal Rubiaceae Eradicate infestations on the Rock Islands; discourage planting; remove planted specimens and any reproduction on Ngerkebesang, Babeldaob and Kayangel.
Tradescantia spathacea kobesos, oyster plant, boat plant, boat lily, Moses in a boat Commelinaceae Discourage further planting and dumping; control outside of cultivation.
Tradescantia zebrina wandering jew Commelinaceae Discourage further planting and dumping; control outside of cultivation.
Turnera subulata white alder Turneraceae Discourage planting; control in sensitive and natural areas.
Turnera ulmifolia yellow alder, sage rose Turneraceae Discourage planting; control in sensitive and natural areas.
* Vitex parviflora small-leaved vitex Verbenaceae Try to locate, eradicate if found.

*High priority for eradication
Eradication can probably be accomplished at low cost


Recommendations by State

All states

The following recommendations apply to all states:

Scientific Name

Common name

Comments and recommendations

Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Discourage further planting; eradicate outside of urban areas, assist landowners in destroying and disposing of unwanted plants.
Clidemia hirta kúi, Koster’s curse Report occurrences outside the generally infested area to Bureau of Agriculture for eradication.
Dieffenbachia seguine dieffenbachia Control outside of cultivation, especially in moist areas.
Dissotis rotundifolia dissotis, pink lady Discontinue planting; discourage dumping of garden waste; control escaped populations as needed.
Epipremnum pinnatum ‘Aureum’ pothos Control outside of cultivation, especially in forested areas.
Imperata cylindrica kasoring, cogon grass Report occurrences outside the known infestations to Bureau of Agriculture for eradication.
Merremia peltata kebeas, merremia Work with Koror and Babeldaob States to evaluate control measures that can be used by landowners
Mikania micrantha teb el yas, mile-a-minute weed Report occurrences to Bureau of Agriculture for eradication.
Spathodea campanulata orsachel kui, African tulip tree Remove existing trees and report new occurrences to Bureau of Agriculture.
Sphagneticola [=Wedelia] trilobata ngesil ra ngebard, Singapore daisy Discontinue planting; discourage dumping of garden waste; control escaped populations as needed.
Syngonium angustatum arrowhead plant Control outside of cultivation, especially in forested areas.
Tradescantia spathacea kobesos, Moses in a boat Discontinue planting; discourage dumping of garden waste; control escaped populations as needed.
Tradescantia zebrina wandering jew Discontinue planting; discourage dumping of garden waste; control escaped populations as needed.

Discourage dumping of garden waste and cuttings. Many tropical species can reproduce vegetatively and dumping of garden waste can spread them to new areas.

Infrequent mowing or slashing may just spread weed species that reproduce vegetatively, including Dissotis rotundifolia, Tradescantia spathacea, Tradescantia zebrina and Wedelia trilobata.

Limit burning and extinguish wildfires promptly. Fire destroys many native species, which are not well adapted to fire, and favors invasive species, many of which are fire-resistant, fire-promoting or are pioneer species that do well on burned sites. Burning favors invasive species by reducing competition, exposing mineral soil and destroying organic matter, making it difficult for native species to become re-established. Fire can promote the reproduction of fire-adapted species, such as Acacia auriculiformis (earleaf acacia), Arundo donax (giant reed), Chromolaena odorata (ngesngesil, chromolaena, Siam weed), Imperata cylindrica (kasoring, cogon grass), Melaleuca quinquenervia (cajeput, paper bark tree), Melinis minutiflora (molasses grass), Panicum maximum (Guinea grass) and Pennisetum polystachion (desum, mission grass). Establishment of these species (and extirpation of native species) can fuel additional fires, leading to a destructive fire cycle.

Disturbance, removal of competition and the exposure of mineral soil favor many invasive species. Undisturbed ecosystems are much more resistant to invasion. Limiting roadbuilding, land clearing and timber harvesting to the minimum necessary and restoring vegetative cover to disturbed sites and roadsides will help prevent the establishment and spread of invasive plant species.

Following are management recommendations for the most serious invasive plant species specific to each state.

Kayangel State

Only a small number of invasive species are present in Kayangel. Island residents should institute voluntary quarantine to prevent further introductions and promptly eradicate undesirable species when found.

Scientific Name

Common name

Comments and recommendations

Thunbergia grandiflora bung el etiu, blue trumpet vine Eradicate if still present.
Timonius timon liberal Eradicate if still present.

Babeldaob States

The completion of the Compact Road may lead to increased problems with invasive plant species on Babeldaob. Vehicle traffic can spread some species along road corridors. Improved access can promote increased disturbance, including roadbuilding, degradation of forest cover and increased risk of wildfire. There will undoubtedly be an increased rate of dispersal of Chromolaena odorata and Pennisetum polystachion northward into areas that are already more fire-prone. Local control is recommended because both species are fire tolerant and fire-promoting species. Pennisetum polystachion in particular causes hot fires.

Aimeliik State

Scientific Name

Common name

Comments and recommendations

Calamus sp. rattan, bangerenguis ra ngebard Evaluate and propose for eradication.
Centratherum punctatum centratherum, lark daisy Eradicate cultivated specimen if still present and any others found.
Chromolaena odorata ngesngesil, chromolaena, Siam weed Check to see if biological control agents are present and if additional ones could be introduced.
Eichhornia crassipes bung el ralm, water hyacinth Evaluate for extent, eradicate if possible.
Melaleuca quinquenervia cajeput, paper bark tree Survey for extent and reproduction; consider control measures to limit spread, particularly in moist areas.
Senna surattensis scrambled eggs Eradicate if of limited extent.
Solanum torvum prickly solanum, devil’s fig Eliminate individual plants; assist landowners in eliminating plants, evaluate for eradication.
Tephrosia candida white tephrosia Evaluate for invasiveness; control if needed.

Airai State

Scientific Name

Common name

Comments and recommendations

Acacia farnesiana Ellington curse, klu Eradicate.
Aeschynomene americana American joint vetch Map extent of infestation, determine if control or eradication is needed.
Calliandra calothyrsus powderpuff, red calliandra Eradicate if of limited extent.
Chloris virgata feather finger grass, feathery Rhodes grass Map extent of infestation and evaluate whether control or eradication is needed.
Episcia reptans flame violet Request or conduct a risk assessment to determine further management action.
Flemingia macrophylla no common name Discontinue planting, monitor for spread.
Imperata cylindrica kasoring, cogon grass Continue eradication project at the airport.
Melia azedarach Chinaberry Eradicate, follow up on distribution.
Pennisetum setaceum fountain grass Eradicate if still present, follow up on distribution.
Pistia stratiotes duckweed, water lettuce Find source, eradicate if feasible.
Pithecellobium dulce kamatsíri, opiuma, Madras thorn Locate any additional specimens; monitor for invasiveness; eradicate if of limited extent.
Spathodea campanulata orsachel kui, African tulip tree Obtain landowner permission to remove last known remaining trees.
Timonius timon liberal Eradicate planted and reproducing tree; search for others and eradicate if found.

Melekeok State

Scientific Name

Common name

Comments and recommendations

Erechtites hieraciifolius fireweed Determine extent of infestation; evaluate for eradication.
Imperata cylindrica kasoring, cogon grass Eradicate.
Melampodium divaricatum blackfoot, golden button Evaluate potential for naturalization and spread (conduct or request a risk assessment).
Thunbergia grandiflora bung el etiu, blue trumpet vine Eradicate.

Ngaraard State

Scientific Name

Common name

Comments and recommendations

Melinis minutiflora molasses grass Monitor spread, particularly after fires.

Ngarchelong State

Scientific Name

Common name

Comments and recommendations

Striga asiatica Asiatic witchweed Map extent of infestation and evaluate for eradication.

Ngatpang State

Scientific Name

Common name

Comments and recommendations

Clidemia hirta Koster’s curse Evaluate for control strategies.
Hyptis pectinata mint weed Evaluate distribution, eradicate if possible.
Melaleuca quinquenervia cajeput, paper bark tree Survey for extent and reproduction; consider control measures to limit spread, particularly in moist areas.
Solanum torvum prickly solanum, devil’s fig Eliminate individual plants; assist landowners in eliminating plants, evaluate for eradication.
Thunbergia grandiflora bung el etiu, blue trumpet vine Eradicate

Ngeremlengui State

Scientific Name

Common name

Comments and recommendations

Senna siamea cassod tree Siamese cassia Eradicate if of limited extent.

Ngiwal State

Scientific Name

Common name

Comments and recommendations

Antigonon leptopus dilngau, chain of love Control outside of cultivation, work to eventually eradicate.

Koror State

Koror, Malakal and Ngerkebesang

Scientific Name

Common name

Comments and recommendations

Antigonon leptopus chain of love Control outside of cultivation, work to eventually eradicate.
Calathea majestica [=C. princeps] no common name Monitor for possible spread and to determine if control or eradication is needed.
Calliandra surinamensis pink powder puff Monitor for spread and eliminate if possible; discourage further planting.
Costus woodsonii Indian-head ginger, red cane Monitor for spread, eradicate if possible.
Eichhornia crassipes bung el ralm, water hyacinth Evaluate for extent, eradicate if possible.
Episcia reptans flame violet Request or conduct a risk assessment to determine further management action.
Flemingia macrophylla no common name Discontinue planting, monitor for spread, eradicate if naturalizing.
Imperata cylindrica kasoring, cogon grass Eradicate if the non-flowering infestation on Ngerkebesang proves to be I. cylindrica.
Inga edulis ice cream bean Investigate source; search for additional introductions; eradicate.
Ipomoea quamoclit asangao, star of Bethlehem Eradicate if of limited extent.
Melia azedarach Chinaberry Eradicate, follow up on distribution.
Pennisetum setaceum fountain grass Eradicate if still present, follow up on distribution.
Thunbergia grandiflora bung el etiu, blue trumpet vine Control outside of cultivation, evaluate for eradication.
Timonius timon liberal Eradicate planted tree on Ngerkebesang and any others found.

Rock Islands

We found few changes in the islands revisited after five years. One thing that may be helping is the activity of the Koror State Rangers in maintaining the cleanliness of these sites. Perhaps this could be taken further by training the Rangers to recognize and remove the more likely introductions and to report suspicious plants to the Invasive Weed Eradication Officers for identification and possible removal.

Recently introduced species were found at the "Survivor" filming site on Ngeremdiu. This and the other filming sites should be monitored to see if additional invasive species turn up. If it was not done in this instance, in the future posting of a "clean-up" bond should be required of film crews and other such permit holders.

Scientific Name

Common name

Comments and recommendations

Chromolaena odorata ngesngesil, chromolaena, Siam weed Extirpate any isolated patches found.
Erigeron bellioides fleabane daisy Eradicate recently established population on Ngemelis.
Sesbania grandiflora sesbania Monitor for spread or eliminate.
Stachytarpheta cayennensis louch beluu, blue rat’s tail Eradicate on Ngidech Island and any other isolated patches.
Timonius timon liberal Eliminate trees on Bkul a Chesemiich, Ngchelobel, Ngeanges (Neco) and Ngerchong islands and wherever else it is found.
Various species Monitor "Survivor" filming sites for new introductions and eliminate those found.

Peleliu and Angaur

Quite a number of species that are present elsewhere in Palau have not yet made it to these two islands and there are also several species present on Peleliu and Angaur that are of concern to other islands (see Appendix 6, Table 3 and Table 5, and Appendix 7, Table 3 and Table 5). It would be desirable to implement some sort of quarantine, even a voluntary one based on public education, to limit the transfer of potentially invasive species to and from these islands. Prompt eradication action should be taken on newly introduced species.

Peleliu State

Peleliu

Scientific Name

Common name

Comments and recommendations

Barleria lupulina hophead Philippine violet Single example; monitor for spread or eradicate
Chromolaena odorata ngesngesil, chromolaena, Siam weed Introduce biocontrol agents.
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Evaluate for possible eradication.
Crotalaria retusa devil-bean, rattlepod Eradicate planted specimens at Dolphin Bay Resort.
Hamelia patens firebush, redhead, scarletbush Discourage further planting; evaluate for eradication.
Pluchea carolinensis sour bush Consider eradication if of limited extent.

 

Ngercheu (Carp Resort)

Scientific Name

Common name

Comments and recommendations

Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Eliminate single example.
Datura metel datura, downy thorn-apple Eliminate single example.
Melia azedarach Chinaberry, pride-of-India, Indian lilac Eliminate single example.
Pereskia aculeata Barbados gooseberry, leafy cactus Eliminate single example.
Timonius timon liberal Assess extent and extirpate if practical to do so.

Angaur State

Scientific Name

Common name

Comments and recommendations

Chromolaena odorata ngesngesil, chromolaena, Siam weed Introduce biocontrol agents.
Clerodendrum quadriloculare kleuang, bronze-leaved clerodendrum Evaluate for possible eradication.
Mimosa diplotricha mechiuaiuu, giant sensitive plant Insure that biological control agents are present; Investigate the feasibility of eradication.

Southwest Islands

Since these islands were not visited during this survey the following recommendations are reproduced from the report on the 2002 survey:

Most of the invasive species present in the rest of Palau have yet to reach the Southwest Islands. Internal quarantine should be implemented to prevent the entry of new pests to these islands.

Exotic animal vectors should be controlled, if possible, including dogs, cats and non-native fruit-eating birds and bats.

Sonsorol State

Sonsorol

Scientific Name

Common name

Comments and recommendations

Bidens alba beggar’s tick Eradicate (burn on site to prevent moving seeds, monitor for reproduction and new infestations and destroy).
Bryophyllum pinnatum life plant Eradicate.
Canna indica canna lily Discontinue planting; control outside of cultivation; consider eradication.
Celosia argentea esechilamalk, cockscomb Discontinue planting; control outside of cultivation; consider eradication.
Duranta erecta golden dewdrop Discontinue planting; control outside of cultivation; consider eradication.
Leucaena leucocephala telengtungd, leucaena Destroy any new seedlings found.
Muntingia calabura budo, Singapore cherry Discontinue planting; control outside of cultivation; consider eradication.
Pseuderanthemum carruthersii Eradicate (request assistance if needed).
Tecoma stans yellow-elder Eradicate.
Tradescantia spathacea kobesos, oyster plant, Moses in a boat Discontinue planting; control outside of cultivation, consider eradication

Pulo Ana

Scientific Name

Common name

Comments and recommendations

Tecoma stans yellow-elder Eradicate.

Merir

Scientific Name

Common name

Comments and recommendations

Muntingia calabura budo, Singapore cherry Consider eradication before it spreads.

Hatohobei State

Tobi

Scientific Name

Common name

Comments and recommendations

Acacia auriculiformis Papuan wattle Discontinue planting; control outside of cultivation; consider eradication.
Canna indica canna lily Discontinue planting; control outside of cultivation; consider eradication.
Casuarina equisetifolia ngas, ironwood Eradicate (single tree).
Pseuderanthemum carruthersii Discontinue planting; control outside of cultivation; consider eradication.
Sansevieria trifasciata kitelel, bowstring hemp Discontinue planting; control outside of cultivation; consider eradication.
Tecoma stans yellow-elder Eradicate.

Helen’s Reef

Scientific Name

Common name

Comments and recommendations

Casuarina equisetifolia ngas, ironwood Eradicate.

Appendix 1.  Invasive plant species of Palau

Appendix 2.  Invasive plant species not known to be present in Palau

Appendix 3.  Invasive species present in Hawai‘i, Guam, Yap, Papua New Guinea, Philippine Islands or Taiwan but not present in Palau

Appendix 4.  Invasive species of environmental concern by location

Appendix 5.  Other invasive species by location

Appendix 6.  Presence of invasive species of environmental concern within Palau

Appendix 7.  Presence of other invasive species within Palau

Appendix 8.  Risk assessments for introduced species in Palau

Appendix 9.  Scientific name synonyms

Appendix 10.  Background material and references


(1) Former Director, Pacific Southwest Research Station, USDA Forest Service (retired); Director of Science, National Tropical Botanical Garden and Forest Health Coordinator, Institute of Pacific Islands Forestry, USDA Forest Service, respectively.

(2) Space, James C., Barbara M. Waterhouse, Joel E. Miles, Joseph Tiobech and Kashgar Rengulbai (2003). Report to the Republic of Palau on invasive plant species of environmental concern. USDA Forest Service, Honolulu, Hawaii. 174 pp.

(3) Space, James C. and Marjorie Falanruw (1999). Observations on invasive plant species in Micronesia. Report prepared for the meeting of the Pacific Islands Committee, Council of Western State Foresters, Majuro, Republic of the Marshall Islands, February 22-26, 1999.

(4) We would like to express our sincere appreciation for the hospitality, assistance and support provided by the Minister of Resources and Development, Fritz Koshiba, and the Director of the Bureau of Agriculture, Fernando Sengebau. We are also much indebted to Ann Kitalong, Vanray Tadao, Sholeh Hanser and Jesse Czekanski-Moir of the Belau National Museum for their enthusiastic participation in the field work and for much-needed assistance in collecting, preparing, drying and curating voucher specimens. We also much appreciated the valuable assistance of Dr. David Brussell of Eastern Illinois University in the short time we had available for surveying Kayangel Atoll. Last but not least, the Palau Conservation Society provided their boat, without which the surveys of Peleliu, Angaur, Kayangel and the Rock Islands would not have been possible.


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This page revised 7 April 2009