Dense Heliocoverpa spp. populations were adequately controlled with frequent applications of a low rate (0.0125 lb ai/a) of cyhalothrin. The addition of diflubenzuron did not increase the efficacy of cyhalothrin. Beneficial insect populations were reduced in plots treated with cyhalothrin, and heavy beet armyworm outbreaks occurred. Fewer beet armyworms were found in plots treated with diflubenzuron + cyhalothrin than in plots treated with cyhalothrin alone, but dense populations developed in both treatments. Diflubenzuron alone did not reduce beet armyworm population density to below those in untreated plots. Yields were higher when Heliocoverpa spp. were controlled (dense beet armyworm populations) than when Heliocoverpa spp. were not controlled and beet armyworm were maintained below damaging levels.