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Conference abstract2008

Biological control of Plutella xylostella: role of generalist predators and enemy-enemy interactions

Björkman, Christer


Introduction: The diamondback moth (Plutella xylostella) is a major pest in large parts of the world. It has developed resistance against almost all known insecticides, including Bt. Efforts to develop biological control have mainly focused on parasitoids. Less emphasis has been on the role of generalist predators. Methods: The density of natural enemies (predators and parasitoids) and level of parasitism was estimated on farms using or not using insecticides in Nicaragua. The level of damage by P. xylostella on cabage plants was estimated on the same farms. An exclusion experiment was performed, on semi-organic farms, to estimate the relative importance of different nataurel enemy types (flying vs. ground-dwelling). Results: The density of generalist predators and parasitoids was higher on farms not using insecticides than on farms using insecticides. This difference translated into a lower damage of cabbage on farms not using insecticides. The exclusion experiment showed that flying and ground-dwelling natural enemies predated upon P. xylostella larvae to a similar extent, when either of them was excluded. However, when both types were allowed to act as enemies, there was a significant negative interaction between them. Conclusions: Generalist predators, especially wolf spiders (Lyocsidae, but also rove beetles (Col.; Staphylinidae), jumping spiders (Salticidae) and damsel bugs (Heteropt.: Nabidae), are important natural enemies of P. xylostella and should be considered when developing biological control programs. The possible negative interaction between different types of natural enemies needs to be explored further to reduce the risk of counterproductive efforts when developing biological control methods

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    UKÄ Subject classification

    Agricultural Science

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