Suitability of Microtheca ochroloma (Coleoptera: Chrysomelidae) for the Development of the Predator Chrysoperla rufilabris (Neuroptera: Chrysopidae).

Abstract

Microtheca ochroloma Stål, the yellowmargined leaf beetle, is one of the most destructive pests of crucifer vegetables on organic farms. Larvae of the green lacewing Chrysoperla rufilabris Burmeister have been observed preying on M. ochroloma, but no studies have evaluated the suitability of M. ochroloma as prey for C. rufilabris or the efficacy of this predator as a biological control agent of the pest. This study quantified the killing rate, developmental time, and survivorship of C. rufilabris when offered eggs and larvae of M. ochroloma at 10, 15, 20, or 25°C. Mean number of prey killed daily increased from 8.4 eggs and 4.0 larvae at 15°C to 18.6 eggs and 10.2 larvae at 25°C. However, predator larvae killed 78% fewer total eggs at 25°C than at 15°C; total number of first-instar prey killed did not vary significantly with temperature. Mean developmental time of predator larvae decreased from 75.5 d at 15°C to 26.6 d at 25°C when they were fed eggs, whereas it decreased from 54.0 d at 15°C to 21.4 d at 25°C when they were fed larvae. Predator survivorship was reduced by 80% at 15°C and no larvae survived at 10°C. We conclude that C. rufilabris can complete development on a diet of eggs of M. ochroloma, but its effectiveness to control M. ochroloma populations will be lessened during cool months, from November to April, when crucifers are produced in Florida and the beetle is actively developing, reproducing, and causing crop damage.