Insecticide selectivity to two species of Trichogramma in three different hosts, as determined by IOBC/WPRS methodology.

Background: The use of Trichogramma species is a potential key strategy in integrated pest management. However, its effectiveness depends on the use of chemicals that do not interfere with parasitism and parasite population growth. Here, a study was made of the effects of synthetic insecticides on Trichogramma pretiosum and Trichogramma exiguum in different hosts (Ephestia kuehniella, Plutella xylostella and Spodoptera frugiperda) and the influence of International Organisation for Biological Control (IOBC/WPRS) methodology in selectivity studies using different Trichogramma species. The insecticides used were commercial formulations (triflumuron at a concentration of 0.2 mL L(-1) water, etofenprox at a concentration of 0.47 mL L(-1) water and endosulfan at a concentration of 7.5 mL L(-1) water); the control treatment consisted of distilled water. Eggs attached to cardboard cards were offered to parasitoids inside glass cages. Parasitised eggs, parasitism and adult emergence rates and parasitism reduction were evaluated.

Results: Endosulfan and etofenprox, classified as class-4 toxic products, were extremely toxic to the parasitoids. Triflumuron, classified as a non-toxic product, was selective to the parasitoids in eggs of all hosts.

Conclusions: The methodology recommended by IOBC/WPRS influenced results regarding the use of different species of parasitoids, and the use of a single parasitoid species in their experiment is questionable.