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Effects of Novel Pesticides on Trichogramma pretiosum

John R. Ruberson, Phillip M. Roberts and Mark R. Abney


ABSTRACT

The effects of several pesticides on the foraging behavior and life history of Trichogramma pretiosum were evaluated. The pesticides tested were: (1) Tracer® (spinosad; Dow AgrosSciences); (2) Steward® (indoxacarb; DuPont); (3) Dimilin® (diflubenzuron; Uniroyal); and (4) Karate Z® (l-cyhalothrin; Syngenta). For the foraging study, eggs were treated with a single rate of each compound, the eggs were allowed to dry, and female parasitoids were each allowed to forage on two eggs. Four behaviors (antennating, stinging, host feeding, and cleaning) were timed and compared among treatments. For the life history study, eggs parasitized 3 days prior were treated with 2 rates of each of the compounds, and the developmental times, emergence rates, parasitoid size (right hind tibia length), female longevity, and fecundity were assessed. Female parasitoids spent significantly less time foraging on both eggs treated with Karate than on eggs treated with Steward and Tracer, where females spent the greatest amount of time. Most of this difference was due to shortened stinging and prolonged cleaning times for females on the Karate-treated eggs, and prolonged stinging times and cleaning times for females on the Steward- and Tracer- treated eggs, respectively. Pesticide treatment significantly affected preimaginal developmental times, but these differences were small and likely of limited biological significance. Parasitoid emergence was adversely affected by Tracer and Karate at both rates, and by Dimilin at the high rate (0.125 lbs AI/A). Females emerging from eggs treated with a low rate of Karate (0.015 lbs AI/A) were significantly larger than females emerging from eggs treated with Dimilin at the low rate (0.03 lbs AI/A) but no other differences were observed in size. Female longevity and offspring production were unaffected by the treatments the females had received while developing in the host egg.





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Document last modified May 20, 2002