Farmer and adviser anecdotal reports stated that fleabane is increasing as a crop weed, especially in the southern part of the WA wheatbelt. In 2007, a survey was conducted across 150,000 square kilometres of the southern region of the WA wheatbelt to determine whether glyphosate resistant fleabane populations were present. Sixty eight fleabane populations were collected from various fields (18%) and roadside locations (79%). These populations were collected from areas which received high summer rainfall and where fleabane was known to exist. Collected populations were screened in 2008 with glyphosate and all populations were found to be glyphosate susceptible. While no glyphosate resistant fleabane populations were found in the south-eastern WA wheatbelt, it is important to monitor the efficacy of glyphosate, especially as glyphosate resistant canola will be grown in WA from 2009 onwards.
Major findings included:
- All 68 fleabane populations collected were susceptible to glyphosate (at label rate)
During March 2018, a total of 94 fleabane populations were collected from roadsides, farmer paddocks and townsite in the southern wheatbelt region of Western Australia. During the 2018 growing season (April/May), fleabane populations were treated with glyphosate and 2,4–D at recommend field rates. These treatments were repeated in September and any plants surviving the glyphosate treatment were grown on for seed. The progeny from these populations were treated with several doses of glyphosate during September 2019 to determine their resistance status. Of the 94 fleabane populations, 11 populations are confirmed resistant to glyphosate, while no populations displayed resistance to 2,4-D. These resistant populations came from roadsides, paddocks and townsites.