The extent of herbicide resistance in

Context Annual ryegrass (Lolium rigidum) is a major weed of crop production in southern Australia that readily develops resistance to herbicides. Resistance increases both yield losses and control costs associated with this species. Aims This study aimed gauge the extent distribution herbicides L. rigidum across south-eastern Australian grain systems by collecting seed from randomly selected fields. Methods A total 1441 populations were collected through random surveys conducted over 5 years 13 agricultural regions four states these samples then tested for eight six modes action. Key results diclofop-methyl sulfometuron-methyl was most common, being present 64% 63% respectively. Glyphosate 4% collected. Only 15% susceptible all tested. Large differences occurred between surveyed ranging 86% 12% 96%. post-emergent tended be higher than pre-emergent Multiple common 60% having two or more herbicide Conclusions There significant multiple individual suggesting rates evolution have differed regions. Implications The high incidence cropping fields highlights need adoption additional practices mitigate impact species on systems.