The effects of an IGR on alfalfa leafcutting bee development

Alfalfa, Medicago sativa, grown for seed is a thriving industry in northern Utah and southern Idaho. As with many perennial cropping systems, there are several insects that are considered pests because they can reduce optimal seed production. In particular, several Lygus spp. are consistently present and can reduce yield by feeding on developing seeds. Unfortunately, managing pests is difficult when alfalfa seed requires alfalfa leafcutting bees, Megachile rotundata, for pollination. An insect growth regulator, Rimon 0.83EC (Novaluron) is considered a reduced risk alternative to reduce lygus bugs while conserving the pollinators; however, the effects of Rimon on the subsequent generation of bees is not well understood. Anecdotal evidence suggested an insect growth regulator may cause mortality to offspring. Six treatments (10x, 2x, 1x, 1/2x, water, blank) were applied directly to alfalfa leafcutting bee eggs. Egg hatch was recorded for each treatment and subsequent larval development was monitored. Results and potential management implications will be discussed.