Effects of recombinant baculoviruses on three nontarget heliothine predators
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abstract
Genetically engineered baculoviruses, relative to their wild-type progenitors, have successfully improved the time-to-kill of these arthropod-specific biopesticides. Beneficial arthropods that prey on targeted pest insects are likely the first nontarget organisms to be adversely affected by the applications of such biopesticides. The goals of this project were to assess potential risks of the recombinant baculoviruses on Solenopsis invicta, Geocoris punctipes, and Hippodamia convergens, all of which are common predators of heliothines in Texas cotton. Four recombinant Autographa californica nuclear polyhedrosis viruses (AcNPV), one Helicoverpa zea nuclear polyhedrosis virus (HzNPV), and two corresponding wild-type NPVs were used in this risk assessment study. Risks associated with these baculoviruses were determined by possible shifts in predator life history traits (rate of food consumption, travel speed, fecundity, and survival) when fed prey infected with recombinant viruses compared to prey infected with wild-type viruses or to healthy prey. We also tested for possible transmission of these viruses by predators using the polymerase chain reaction (PCR). No significant shifts in life history characteristics were detected in predators fed Heliothis virescens larvae infected with any of the seven viruses. Viral DNA was discovered using PCR in 2.3% of fire ant workers, but not from any of the queens or eggs. In G. punctipes, 13.4% of adults and 0.5% of eggs scored positive for viruses. Twelve percent of H. convergens adults were found PCR positive. Residency in all three predators tested provides a pathway which could increase the persistence of recombinant viral particles in the environment and thus may produce an indeterminable amount of risk associated with their inadvertent movement.
