Effects of a protease-expressing recombinant baculovirus on nontarget insect predators of Heliothis virescens

Abstract

Abstract The baculovirus AcMLF9.ScathL expresses a basement membrane-degrading protease and represents a new class of recombinant baculovirus insecticides. Risk assessment studies were conducted according to the requirements of the US Environmental Protection Agency to investigate potential negative effects of consumption of Heliothis virescens larvae infected with AcMLF9.ScathL, on two common predators, the lacewing Chrysoperla carnea , and the ladybird beetle Coleomegilla maculata . Predators were reared on one of three feeding regimes consisting of H. virescens larvae that were uninfected or infected with AcMLF9.ScathL or AcMNPV C6. Control regimes consisted of Sitotroga cerealella eggs for C. carnea and Ostrinia nubilalis eggs and aphids for C. maculata . Survival of C. carnea fed Sitotroga eggs or AcMLF9.ScathL-infected H. virescens was significantly higher than for C. carnea fed H. virescens that were uninfected or infected with AcMNPV C6. There were no significant differences in development rates between C. carnea fed H. virescens infected with AcMNPV C6 or AcMLF9.ScathL. Baculoviruses ingested by C. carnea larvae remained viable within the digestive tract until adult emergence but had no detrimental effect on egg production. There was no evidence of adverse effects of AcMLF9.ScathL on C. maculata although this species exhibited low survival on diets composed exclusively of H. virescens . In choice tests, neither predator exhibited a preference between uninfected H. virescens and H. virescens infected with AcMNPV C6 or AcMLF9.ScathL. The data suggest that use of AcMLF9.ScathL in pest management would pose no greater risk to insect predators in the environment than use of the wild-type virus AcMNPV C6.