Japanese beetle: Management decisions

Japanese beetles release a strong aggregation pheromone, and are commonly seen feeding and mating in clusters. Adults are also highly mobile and move frequently in the summer. Japanese beetle can build up to economically damaging populations in soybean, but their defoliation is typically overestimated (see previous tab for examples). In soybean, adults prefer to feed on the upper leaf surface. The treatment threshold for Japanese beetles in soybean is 30 percent defoliation before bloom and 20 percent defoliation after bloom through seed set. Because adults are highly mobile, remember to continue scouting through to seed set. Migrating adults could reinfest the field in after knocking down an initial population.