Ingestion and Defecation of Recombinant and Wild-Type Nucleopolyhedroviruses by Scavenging and Predatory Arthropods

Abstract

Wild-type and recombinant nucleopolyhedroviruses (NPVs) were compared with respect to their potential for environmental transport by the predatory spined soldier bug Podisus maculiventris (Say), the scavenging fly Sarcophaga bullata (Parker), and the house cricket Acheta domesticus (L.). Viruses tested were variants of Autographa californica (Speyer) NPV (AcNPV): wild-type virus (AcNPV.WT), AcNPV expressing a scorpion toxin (AcNPV.AaIT), and AcNPV expressing a mutated juvenile hormone esterase (AcJHE.SG). All three insects ingested Trichoplusia ni (Hubner) larvae infected with or killed by each of the three NPVs. The type of virus that killed T. ni larvae did not affect feeding preference of the cricket or fly. The cumulative survival curves for the three nontarget insects did not depend on whether they ingested AcNPV.WT-infected, recombinant-infected, or uninfected T. ni. Thus, direct effects of the recombinant viruses on nontarget organisms probably are similar to those by wild-type NPV. Within 5 d after ingesting virus-infected larvae, all three nontarget insects voided >1,000 times the median lethal dose of each NPV against neonatal Heliothis virescens (F.). All three insects defecated significantly more AcJHE.SG virus than the other viruses. Thus, AcNPV.AaIT and AcJHE.SG potentially can be transported away from a release site by the predator and the two scavengers and thereby contact additional nontarget species.