Italian ryegrass is a major weed in orchards, vineyards, field crops and fallow fields of California (Figure 1). Several different herbicides are used to control ryegrass and had been effective in reducing infestations until resistance evolved in many populations following repeated use of the herbicides. To date, resistance to glyphosate, paraquat, and some ACCase and ALS inhibitors has been confirmed in ryegrass infestations across the agricultural landscape of California. To make matters worse, resistance to multiple postemergence herbicides with different modes of action has been confirmed within the same orchard, vineyard, or field in some areas. Consequently, management of Italian ryegrass in California annual and perennial...