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Impact of recombinant baculovirus applications on target heliothines and non-target arthropods in cotton
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Recombinant baculoviruses have been genetically engineered to reduce the time to kill infected pests with a goal of reducing crop damage. In this study, recombinant and wild type viruses were applied to cotton in response to larval infestations of Helicoverpa zea Boddie and Heliothis virescens (F.) in 1997 and 1998. An insecticide treatment and an untreated control acted as standards upon which to base comparisons. The goals of this field study were to: (1) Assess the efficacy of recombinant baculoviruses in protecting cotton from larval feeding damage; (2) Assess the impact of recombinant virus introductions on non-target beneficial arthropods; (3) Determine if predators and parasitoids acquire baculoviruses through the consumption of infected heliotropes. Thirty-two research plots, arranged in an 8 x 4 grid, were located within a large commercial cotton field, and the eight treatments of study were replicated four times each. When applications were timed at larval emergence, recombinant viruses protected cotton from damage statistically better than wild type virus treatments and as well as the insecticide. Differences in efficacy between recombinant and wild type baculoviruses were not significant if treatments were applied three to four days after peak larval emergence. Contrasts of treatment effects on predator populations and developing Microplitis croceipes (Cresson) endoparasitoids found no differences among recombinant and wild type viruses. Predator population densities and parasitoid size, emergence percentages, and sex ratios were not statistically different among recombinant and wild type virus treatments. From polymerase chain reaction analyses of predators collected from treatment plots in 1997 and 1998, 1.7% and 0.2%, respectively, of predators were found to have consumed a virus-infected heliothine. Nine of the 26 predators carrying viral DNA were positive for recombinant virus. Additionally, 13 of the 26 predators were found to disperse 13.5 to 105 meters two to five days after initial virus applications. Five of these dispersing predators (0.2% of all predators evaluated) carried recombinant viral DNA. Molecular analysis also found no detectable viral DNA in any of the emergent M croceipes. These results suggest the potential for inadvertent spread of recombinant viral DNA via dispersing predators and parasitoids is possible but low.
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Includes bibliographical references (leaves 90-97).
Issued also on microfiche from Lange Micrographics.
Smith, Chad Richard (1999). Impact of recombinant baculovirus applications on target heliothines and non-target arthropods in cotton. Master's thesis, Texas A&M University. Available electronically from
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