Date of Award

1999

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Entomology

First Advisor

James R. Fuxa

Abstract

Wild-type and recombinant nucleopolyhedroviruses (NPVs) were compared with respect to their capability to produce epizootics in Trichoplusis ni (Hubner) larvae infesting collards in a greenhouse microcosm. 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 juvenile hormone esterase (AcJHE.SG). Epizootics of AcNPV.WT lasted 8 weeks after a single viral release in the replicated, greenhouse micro-plots. AcJHE.SG epizootics also lasted 8 weeks after viral release, but this virus and AcNPV.AaIT were both out-competed by AcNPV.WT. AcNPV.AaIT was no longer detected in the T. ni population by the fourth week after release. AcNPV.WT also increased to greater numbers in soil than AcNPV.AaIT or AcJHE.SG after 8 weeks. Both AcNPV.WT and AcJHE.SG had random dispersion patterns in soil. The predator Podisus maculiventris (Say), the scavenging fly Sarcophaga bullata (Parker), and scavenging house crickets Acheta domesticus (Linnaeus) were compared for their capability to transport the wild-type and recombinant viruses. All three insects ingested T. ni larvae infected with or killed by each of the three NPVs. Neither the cricket nor the fly preferred T. ni larvae killed by one type of NPV versus the others. The cumulative survival curves for the three non-target organisms (NTO) did not differ significantly whether they ingested AcNPV.WT-infected, recombinant-infected, or uninfected T. ni. Within 5 days after ingesting virus-infected larvae, all three NTO voided >1000X the median lethal dose of each NPV against neonatal Heliothis virescens (Fabricius). All three insects defecated significantly more AcJHE.SG than the other viruses. Prevalence and spread of the three viruses were compared in the greenhouse microcosm in the presence and absence of one or more of the NTO. Podisus maculiventris transported AcNPV.WT and S. bullata transported AcNPV.WT and AcNPV.AaIT. All three viruses were detected outside viral release sites, indicating that host larvae and abiotic agents may have contributed to viral transport. Prevalence and transport of AcNPV.WT were greater than AcNPV.AaIT and AcJHE.SG regardless of whether the NTO carriers were present or absent.

ISBN

9780599636163

Pages

151

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