Impact of recombinant Baculovirus applications on target heliothines and nontarget predators in cotton

Recombinant baculoviruses have been genetically engineered to reduce the ti me to kill infected pests, thus reducing crop damage. In this study, wild-t ype viruses and recombinant viruses expressing a scorpion toxin were applie d to cotton in response to larval infestations of Helicoverpa tea and Helio this virescens in 1997 and 1998. A chemical standard and an untreated contr ol acted as comparison treatments. The goals of this field study were to (1 ) assess the efficacy of recombinant baculoviruses in protecting cotton fro m larval feeding damage; (2) assess the impact of recombinant virus introdu ctions on predator densities and diversity; and (3) determine if cotton pre dators acquire baculovirus by consuming infected heliothines. When applicat ions were timed at larval emergence, certain recombinant virus treatments p rotected cotton from damage better than wild-type virus treatments and as w ell as the chemical standard, Differences in efficacy between recombinant a nd wild-type baculoviruses were not apparent if treatments were applied 3 t o 4 days after peak larval emergence. Predator densities and diversity were similar among recombinant and wild-type baculovirus treatments, whereas pl ots treated with the chemical standard had consistently smaller predator po pulations. From polymerase chain reaction analyses of predators in 1997 and 1998, 1.7 and 0.2%, respectively, of predators had consumed a virus-infect ed heliothine. Nine of the 26 predators carrying viral DNA were positive fo r recombinant virus. Additionally, 13 of the 26 predators were found to dis perse 13.5 to 105 m 2 to 5 days after initial virus applications. Five of t hese dispersing predators (0.2% of all predators evaluated) carried recombi nant viral DNA, These results suggest that the potential for the inadverten t spread of recombinant viral DNA via dispersing predators is low. (C) 2000 Academic Press.