Wildtype and recombinant baculoviruses for management of insect pests

Boughton, Anthony
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Wildtype and recombinant baculoviruses have potential for managing many serious agricultural pests. The black cutworm, Agrotis ipsilon (Hufnagel), is a serious pest of many crops worldwide. We have characterized a new baculovirus, the Agrotis ipsilon multicapsid nucleopolyhedrovirus (AgipMNPV), that was isolated from A. ipsilon. Restriction enzyme analysis showed AgipMNPV to be distinct from previously described nucleopolyhedroviruses, while electron micrographs of AgipMNPV polyhedra showed that virions contained multiple nucleocapsids. AgipMNPV was highly active against A. ipsilon. Four of seven other noctuid species tested, were also susceptible to infection by AgipMNPV. Studies were performed to assess the potential of AgipMNPV and a viral enhancing agent M2R, for suppression of A. ipsilon. AgipMNPV was highly active against third-instar A. ipsilon. The optical brightener MZR significantly reduced LD50 estimates by 160-fold, but had no direct effect on survival time estimates. In greenhouse and field trials, AgipMNPV significantly reduced feeding damage to corn seedlings caused by third-instar A. ipsilon, but there were no improvements in virus performance attributable to the inclusion of M2R in AgipMNPV formulations. In an appropriately designed pest management program, AgipMNPV could be used to suppress populations of A. ipsilon .;AcMLF9.ScathL is a new recombinant baculovirus that expresses a basement membrane degrading protease. Laboratory studies were conducted to assess potential negative impacts on the predator Coleomegilla maculata (Degeer), arising from consumption of Heliothis virescens F. larvae infected with AcMLF9.ScathL. Control groups of C. maculata were fed mock-infected H. virescens, H. virescens infected with wildtype AcMNPV, or European corn borer, Ostrinia nubilalis (Hubner), eggs and green peach aphids, Myzus persicae (Sulzer). There was no significant difference in C. maculata survival between the three H. virescens feeding regimes. Mean survival time of C. maculata larvae fed on mock-infected H. virescens was significantly longer than C. maculata fed on virus infected H. virescens, possibly due to lower nutritional quality of virus-infected prey. There were no significant differences in survival times between C. maculata fed H. virescens infected with AcMLF9.ScathL or AcMNPV. These data suggest no greater threat to nontarget organisms from the use of AcMLF9.ScathL as a microbial insecticide than would occur with AcMNPV.