Glyphosate resistance in Australian cotton farming systems: what are the surveys telling us? The then and now

Abstract

Key findings • Glyphosate resistance is increasing in 6 common weeds of cotton: annual ryegrass, barnyard grass, feathertop Rhodes grass, fleabane, sowthistle and windmill grass. • Species shift has occurred from pre-GM cotton to 2020. • An increase in zero tillage in dryland cotton has resulted in more surface germinating weeds. • Over 90% of fleabane seed collected was glyphosate resistant. • Glyphosate resistance levels are also increasing in sowthistle, windmill grass and barnyard grass. • Feathertop Rhodes grass resistance is increasing quickly. • Over 80% of annual ryegrass samples tested were glyphosate resistant.