Side effects of bioinsecticides used to control Tuta absoluta


Abstract: Integrated Pest Management (IPM) programs may include pesticide applications,therefore assessing their potential side effects on biocontrol agents is of primary importance forimplementing IPM. Bracon nigricans (Hymenoptera: Braconidae) is a larval ectoparasitoid ofLepidoptera species which was recovered on the South American tomato pinworm, Tuta absoluta(Lepidoptera: Gelechiidae), in various Western Palaearctic countries and is a potential biocontrolagent of this pest. We assessed acute toxicity and sublethal effect on fertility of sixbioinsecticides, used for controlling T. absoluta, on B. nigricans. The tested chemicals wereabamectin, azadirachtin, borax salt plus citrus essential oil, Bacillus thuringiensis var. kurstaki,emamectin benzoate and spinosad. The wasps were exposed for three days to dried pesticideresidues on tomato sprouts, at two time intervals after initial treatment. Mortality was dailychecked and the number of adult parasitoids emerged was recorded to assess the effects onreproduction. These data were used to calculate reduction coefficients and the pesticides wereclassified according to the IOBC toxicity categories. The obtained data were then discussed withthe results of a previous study, conducted with the same experimental setting, on the generalistpredator Orius laevigatus (Heteroptera: Anthocoridae). The insecticides greatly differed in theirtoxicity as well as in their persistence and the effects varied also between the two biocontrolagents. Our findings would help to optimize future use of the tested insecticides in IPM andorganic farming, notably by preventing the possible side effects of the tested pesticides onbiological control agents, both naturally present and artificially released. Furthermore, these resultsstress the need to careful select the chemicals for efficient IPM programs on tomato crops.

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