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1 April 2012 Effect of Insecticides and Plutella xylostella (Lepidoptera: Plutellidae) Genotype on a Predator and Parasitoid and Implications for the Evolution of Insecticide Resistance
Xiaoxia Liu, Mao Chen, Hilda L. Collins, David Onstad, Rick Roush, Qingwen Zhang, Anthony M. Shelton
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Abstract

In the laboratory and in cages in the greenhouse, we evaluated the toxicity of two insecticides (lambda-cyhalothrin and spinosad) on the parasitoid, Diadegma insulare (Cresson), and the predator, Coleomegilla maculate (DeGeer), both natural enemies of the diamondback moth, Plutella xylostella (L.). Lambda-cyhalothrin was very toxic to both natural enemies. Spinosad was less toxic to C. maculata adults and larvae, and slightly toxic to D. insulare. Both natural enemies suppressed P. xylostella populations in cages with 80% spinosad-treated and 20% nontreated plants; such suppression was not seen when lambda-cyhalothrin was used. Using broccoli, Brassica oleracea L. variety italica, a common host for P. xylostella, we also studied direct and indirect effects of both natural enemies in the presence and absence of the two insecticides and to different P. xylostella genotypes: resistant to the insecticide, susceptible, or heterozygous. Neither natural enemy could distinguish host genotype if P. xylostella were feeding on nontreated plants. They could also not distinguish between larvae feeding on spinosad-treated plants and nontreated plants, but D. insulare could distinguish between larvae feeding on lambda-cyhalothrin treated and nontreated plants. Our studies suggest that lambda-cyhalothrin has direct toxicity to these two natural enemies, can affect their host foraging and acceptance of P. xylostella and consequently would not be compatible in conserving these natural enemies in a program for suppression of P. xylostella. In contrast, our studies suggest that treatment with spinosad has much less effect on these natural enemies and would allow them to help suppress populations of P. xylostella. These findings are discussed in relation to the evolution of insecticide resistance and suppression of the pest populations.

© 2012 Entomological Society of America
Xiaoxia Liu, Mao Chen, Hilda L. Collins, David Onstad, Rick Roush, Qingwen Zhang, and Anthony M. Shelton "Effect of Insecticides and Plutella xylostella (Lepidoptera: Plutellidae) Genotype on a Predator and Parasitoid and Implications for the Evolution of Insecticide Resistance," Journal of Economic Entomology 105(2), 354-362, (1 April 2012). https://doi.org/10.1603/EC11299
Received: 5 September 2011; Accepted: 30 January 2012; Published: 1 April 2012
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KEYWORDS
biological control
diamondback moth
host genotype
insecticide
resistance
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