Glasshouse experiment testing two sowthistle populations for glyphosate resistance – 2013

Abstract

Key findings • Fallows, glyphosate tolerant crops and non-cropping areas are under threat from another glyphosate resistant species. • Group B resistance is present in sowthistle populations within the Qld/NSW border region. It is likely that plants will develop multiple resistance to Groups B and M over time. • With the partial loss of effectiveness of glyphosate and Group B resistance in other parts of the northern grain region, there will be more selection pressure on Group I chemistry. Further to this point, herbicide Groups C, G, H and L could be used more to take selection pressure off Groups B, I and M. • Due to its wind borne seed, glyphosate resistant sowthistle populations will spread rapidly, similar to fleabane. Surveys are presently underway to gauge the spread of resistance in the northern grain region. In time, southern regions should be surveyed to determine the extent of resistance to glyphosate in sowthistle populations.