Tritrophic interactions among Bt (Cry3Bb1) corn, aphid prey, and the predator Coleomegilla maculata (Coleoptera: Coccinellidae)

Abstract

The ability of the transgenic corn rootworm resistant corn (Zea mays L.) hybrid, MON 863, to affect the predator Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae) through the consumption of corn-fed aphid (Rhopalosiphum maidis, Homoptera: Aphididae) prey was examined in the laboratory. Aphid weight was used as an index of prey quality. Larvae of C. maculata were reared to pupation on aphids that had consumed transgenic or nontransgenic (susceptible) corn plants. Larval duration, survivorship to pupation, postmortem adult dry weight (taken at 30 d after eclosion), adult mobility, and fecundity were compared for C. maculata between treatments. Fitness parameters of C. maculata were similar between transgenic and susceptible treatments, despite a 33% reduction in the weight of aphid prey reared on MON 863. Using immunostrip tests, Cry3Bb1 was detectable in the leaves of MON 863 but not in the susceptible plant, aphids, or C. maculata that were fed aphids. We conclude that transgenic corn that expresses Cry3Bb1 does not inflict acute or chronic degradations in fitness on individual C. maculata through aphid prey, but these results do not necessarily apply to other natural enemies, herbivores, or insect-resistant corn hybrids.