Detection and Management of herbicide-resistant annual ryegrass in Kentucky wheat

Justification: Annual ryegrass is a weed in Kentucky wheat acres that has become a major pest for many producers. Control of annual ryegrass has been limited to a handful of group 2 or ALS-inhibiting herbicides within wheat. The repeated use of these few herbicides within the same herbicide mode of action has led to selection of ALS-resistant annual ryegrass populations in Kentucky wheat fields. There are also some initial reports of possible resistance to pinoxaden a group 1 herbicide that is one of the few alternatives to the group 2 herbicides. The loss of herbicides due to resistance will further extenuate the challenge of controlling annual ryegrass in wheat. Investigations of additional methods for controlling annual ryegrass in wheat beyond the ALS-inhibiting herbicides is warranted not only for controlling resistant ryegrass, but also for mitigating further resistance events. Objectives: 1. Evaluate annual ryegrass populations for resistance to multiple herbicide sites of action including ALS-inhibiting herbicides. 2. Evaluate additional herbicides and herbicide application timings for control of annual ryegrass and crop safety on wheat. Research Methods: Annual ryegrass populations that have been submitted to Kentucky weed science by growers that are potentially resistant will be subjected to low and high dose applications of herbicides and evaluated for plant survival in the greenhouse. Populations that have highest levels of survivors will be subjected to dose response curves to determine levels of resistance as compared to a susceptible population. Small plot research will be conducted to evaluate non-group 2 herbicides for safety on wheat as well as overall efficacy on ryegrass. Ideally the experiment would be conducted on a population of ALS- resistant ryegrass on a private grower's field. Timing of herbicide applications will also be evaluated to determine the most appropriate timing not only for annual ryegrass control but also wheat safety.