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14 January 2003Detection of the exotic weed Onopordum acaulon L. subsp. acaulon in TasmaniaSubmitted by the Principle Weed Management Officer, Department of Primary Industries, Water and Environment (DPIWE), TasmaniaPurposeFor Information and Comment.Background- A specimen was submitted to the Tasmanian Herbarium on December 6th 2002 and identified as Onopordum acaulon L. subsp. acaulon € stemless thistle.- The stemless thistle was found on a grazing property near Melton Mowbray in the Southern Midlands. The current infestation consists of approximately 20 plants that are nearing maturity. These range in diameter from 25cm to >50cm. The plants occur in pasture and are confined to areas along or near to fence lines that were used for the feeding out of grain during the drought period 1999-2001. - The owner has removed all stemless thistles he has found before they have had a chance to set seed. He also noted that, although the flowers appeared well developed and fluffy, they were not ready to release seed. This fact was confirmed by dissection of herbarium specimens.- The source of the stemless thistle is not certain. However, it is highly likely that the seed has been introduced to the property as a contaminant of feed grain that was imported during the 1999-2001 drought period. This grain was purchased from a feed grain wholesaler who had sourced the grain from either NSW or WA. Both states are possible sources of stemless thistle seed contamination.Issues- This is the first record of stemless thistle in Tasmania. - There is a very high probability that further infestations exist, given the nature of feed grain distribution during the period 1999-2001. - Stemless thistle originated from the western Mediterranean region. It is a weed in southern Australia, particularly in the lower rainfall cereal areas where it commonly occurs in volunteer pastures. It has also shown to infest wetter areas indicating it could grow in a wide range of environments.- Stemless thistle is rarely eaten by stock therefore the carrying capacity of heavily infested land is reduced. When stock have been forced to eat the plant cases of suspected liver poisoning have occurred.- Stemless thistle is a Declared Weed under the Tasmanian Weed Management Act 1999 through the declaration of all "Onopordum spp." Under the Draft Weed Management Plan for "Onopordum spp." all populations of this species are scheduled for eradication. There is therefore the legal capacity to enforce this course of action if necessary.Actions1. Eradicate current infestation before there is a chance for a soil seed store to develop. The landholder is committed to eradicating this weed, and has begun regular surveys of the infested area.2. Trace-back activities will be undertaken by DPIWE in an attempt to determine source of thistle. 3. Inform the farming community in particular, of the seriousness of this pest. This will be achieved by distributing awareness material through peak farming bodies - TFGA and TAPG.4. Tasmania€s Weed Alert Network to be informed and provided with identification information via its newsletter.5. Relevant federal, State and Territory agencies to be notified through the Australian Weeds Committee.6. Other States and Territories to be notified through rapid response/weed alert networks, where these exist.7. A monitoring and surveillance program will be developed and implemented.


The Hawaiian Ecosystems at Risk (HEAR) project is currently funded by the Pacific Basin Information Node (PBIN) of the National Biological Information Infrastructure (NBII) through PIERC (USGS) with support from HCSU (UH-Hilo). More details are available online. Pacific Basin Information Node (PBIN)National Biological Information Infrastructure (NBII)

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This page was created on 13 September 2007 by PT, and was last updated on 13 September 2007 by PT based on data from Rod Randall's Global Compendium of Weeds database dated 24 January 2007. Valid HTML 4.01!