Evaluation of Diatomaceous Earth (Insecto) and Bacillus thuringiensis Formulations for Insect Control in Stored Peanuts²

Runner variety peanuts treated with four rates of diatomaceous earth (28.4, 56.8, 85.2, and 113.6 g per 12.7 kg peanuts) and Virginia variety peanuts treated with four Bacillus thuringiensis formulations (Dipel, Foil, M-Trak and Trident) were held for 8 months at ambient conditions in south Georgia and infested with stored-product insect pests. No red flour beetle, Tribolium castaneum (Herbst), adults were found in peanuts treated with diatomaceous earth until six months after treatment. After 8 months, red flour beetle populations in peanuts treated with diatomaceous earth ranged from 5.7 ± 1.9 to 32.8 ± 12.0 per kg, as compared to 221.2 red flour beetles per 12.7 kg peanuts in untreated controls. The effect of diatomaceous earth on red flour beetles was described by non-linear regression. Indianmeal moth, Plodia interpunctella (Hübner), and almond moth, Cadra cautella (Walker), populations were not abundant in untreated controls or the diatomaceous earth treatments. After 8 months, red flour beetle populations in peanuts treated with the four biological insecticides were not significantly different from the untreated controls. Low levels of Indianmeal moth and almond moth were present in all treatments.