Effects of Insecticide and Tolerant Alfalfa Cultivars on Potato Leafhopper (\u3cem\u3eEmpoasca fabae\u3c/em\u3e) Populations and Forage Yields in Quebec (Canada)

The potato leafhopper [PLH, Empoasca fabae (Harris)], which affects several crops including alfalfa (Medicago sativa L.), is a recurrent problem in several regions of Quebec. The objective was to evaluate alfalfa management tools in order to reduce yield losses caused by this pest. An experiment was conducted at two sites in Quebec over three field seasons to evaluate the impact of insecticide applications and the use of PLHtolerant cultivars on forage yield and PLH populations. Foliar insecticide applications in the seeding year reduced PLH populations but generally failed to impact alfalfa yields compared to untreated alfalfa. However, in one experiment at one site, applications done in the seeding year resulted in increased first-cut alfalfa yields in the post-seeding year compared to untreated alfalfa, even if PLH populations were low. Differences in yields between PLH-tolerant and PLH-susceptible cultivars were minimal in the seeding and post-seeding years regardless of the PLH population levels. However, two PLH-tolerant cultivars produced lower yields compared to other cultivars in the post-seeding year at one site. Preliminary results suggest that foliar insecticide applications could be a more effective way to reduce PLH populations than PLH-tolerant cultivars. However, more data will be required to confirm these results and determine the impact of these management tools on alfalfa yields