Herbicide resistance in wild oats (Avena spp.) in southern New South Wales

A random survey across the southern cereal cropping zone of New South Wales was conducted in 2007 to determine the extent of herbicide resistance in wild oat populations. In total, 113 samples were collected from the 181 properties visited. These samples were screened against the herbicide Groups (A, B, J, M and Z) commonly used for wild oat control in Australia. Resistance was present to Group A 'fop' (38%) and Group Z (10%) herbicides, increasing from 5% and 0% respectively in previous surveys (1991 and 1994).No samples were found to be resistant to clethodim, mesosulfuron, triallate or glyphosate. The significant increase in the incidence of resistance to Group A 'fop' and Z herbicides, combined with a high level of resistance in annual ryegrass from these sites, highlights the importance of adopting an integrated approach to weed management. Such an approach is also necessary for maintaining a nil or low level of resistance in Groups B, J and M, and extending the commercial life of these effective chemicals.