Effects of biological insecticides on the sugarcane aphid, Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), in sorghum

摘要

Melanaphis sacchari (Zehntner) is a major pest of sorghum, Sorghum bicolor (L.) Moench, in the United States and neighboring Caribbean countries including Haiti. Laboratory, greenhouse, and field experiments were conducted to determine the effects of biological insecticides on M. sacchari infesting sorghum. Azadirachtin, pyrethrins, Beauveria bassiana strain GHA, Isaria fumosorosea Apopka strain 97, Chromobacterium subtsugae strain PRAA4-1(T), Burkholderia spp. strain A396, and vetiver oil were compared to a conventional insecticide, flupyradifurone. In the laboratory, sorghum leaf discs were sprayed with treatment solutions and subsequently infested with M. sacchari nymphs. In the greenhouse, potted sorghum plants were sprayed with treatment solutions before or after infestation with M. sacchari nymphs. In the field, plots exposed to natural M. sacchari infestations were sprayed with treatment solutions. All insecticide treatments except I. fumosorosea and Burkholderia spp. were associated with 58-100% aphid mortality after 72 h in the laboratory, which was greater than the 20% mortality observed in the non-treated control. In the greenhouse, azadirachtin and pyrethrins were the biological insecticides associated with the lowest aphid infestation levels 7 days after treatment. Flupyradifurone was associated with the greatest mortality in the laboratory and the lowest infestation levels in the greenhouse. In the field, decreases in aphid infestation levels relative to the non-treated control were not observed although flupyradifurone was consistently associated with the lowest infestations. Our results suggest that biological insecticides including azadirachtin, pyrethrins, and B. bassiana could potentially control M. sacchari infestations in sorghum if applied under favorable environmental conditions.