Effects of imidacloprid seed treatment on greenbug (Homoptera: Aphididae) infestations on three sorghum hybrids

Seed of each of three sorghum hybrids was treated with two different rates of imidacloprid insecticide (1.25 and 2.5 g AI/kg seed) or left untreated, Both rates of imidacloprid reduced greenbug abundance when populations occurred on seedling plants within 2 wk of planting. During both years of the study, the 2.5 g rate of imidacloprid usually significantly suppressed greenbug populations for 60 to 80 days after planting on the greenbug-susceptible hybrid, but the differences were not as noticeable on the greenbug-resistant hybrids. Yields were improved significantly by using the 2.5 g rate of imidacloprid on the greenbug-susceptible hybrid in 1993 when greenbugs exceeded 1,000 per plant in the untreated plots, but not in 1994 when the highest level of greenbugs observed was about 300 per plant. The data show that the higher rate of imidacloprid will be needed to provide late-season greenbug suppression and suggest that imidacloprid can reduce yield losses from late season greenbugs on greenbug-susceptible hybrids.