The extent of herbicide resistance in Tasmanian wild radish populations

Weeds are one of the major limiting factors in cropping systems and the development of resistance to herbicides used for their control can result in increased cost and complexity in managing these weed populations. With
a high proportion of wild radish populations in Western Australia resistant to herbicides, along with a lower proportion in southern New South Wales it could be expected that some Tasmanian populations would also be resistant even though herbicide resistance in Tasmanian ryegrass populations occurs at a lower frequency than many other regions of Australia. For this reason wild radish seed samples were collected as part of a field survey of Tasmanian cropping paddocks in January 2015 to determine the extent of herbicide resistance in a number of weed species. A total of 75 paddocks in Tasmania were visited just prior to harvest from which 25 wild radish samples were collected, the second most common weed behind ryegrass. The samples were screened between March and May 2015 to six herbicides (chlorsulfuron, imazamox/imazapyr, atrazine, diflufenican, 2,4-D amine and glyphosate). The results from the screening will be compared with results from surveys conducted in Western Australia and southern New South Wales and the reasons for differences discussed.