Selectivity and residual effects of some pesticides used to control the South American Tomato Pinworm on two natural enemies: the predator Orius laevigatus and the parasitoid Bracon nigricans

Integrated Pest Management (IPM) programs usually include pesticide applications, therefore assessing their potential side effects on biocontrol agents is of primary importance for implementing IPM. The predator Orius laevigatus (Fieber) (Hem.: Anthocoridae) plays a key role in the control of various arthropod pests, and Bracon nigricans (Szépligeti) (Hym.: Braconidae) is a larval ectoparasitoid of Lepidoptera species which can be an effective biological control agent of South American tomato pinworm Tuta absoluta (Meyrick) (Lep.: Gelechiidae) on tomato in Europe. We assessed acute toxicity and sublethal effects of 14 pesticides, used for management of T. absoluta on tomato, on O. laevigatus adults and on B. nigricans pupae and adults. The tested chemicals were five biopesticides, four synthetic insecticides, two sulphur compounds and three adjuvants. The biocontrol agents were exposed for three days to dry pesticide residues on tomato sprouts, at various increasing intervals after initial treatment. Mortality was daily checked and to assess the sublethal effects on reproductive potential, the emerged nymphs of the predator, the number of eggs laid by the parasitoid and the rate of adult parasitoids emerged were recorded. These data were used to calculate reduction coefficients and the pesticides were classified according to the IOBC toxicity categories. The pesticides greatly differed in their toxicity as well as in their persistence and these results stress the need for careful selection of pesticides to be used in tomato crops for efficient IPM programs.