Effect of Greenbug (Hemiptera: Aphididae) from Resistant Sorghum on Developmental Rates of Convergent Lady Beetle (Coleoptera: Coccinellidae)

Abstract

Understanding tritrophic effects of resistant crops on natural enemies feeding on pests is important for developing resistant plants while conserving natural enemies. The effect on convergent lady beetles, Hippodamia convergens Guerin-Meneville, fed greenbugs, Schizaphis graminum (Rondani), reared on resistant sorghum, Sorghum bicolor (L.) Moench, was assessed. Convergent lady beetles from sorghum fields were paired and allowed to mate. F1 progeny were reared at a photoperiod of 14:10 light:dark hours at 23 or 30°C and fed daily with a known number of biotype I greenbugs from resistant PI550607 or susceptible RTx430 sorghum. Lady beetle eggs hatched 1 day later at 23°C (3.0 days) than at 30°C. Larvae completed development in 0.75 more day and pupae developed in 6.0 versus 3.0 days at 23 than at 30°C. Lady beetles consumed similar numbers of greenbugs from either genotype of sorghum, but larvae and adults consumed 1.7 and 2.5 times more greenbugs at 23 than at 30°C, respectively. Each lady beetle adult at ...