Effects of deltamethrin on the specific discrimination of sex pheromones in two sympatric Trichogramma species.

The large amounts of insecticides used for crop protection lead to widespread environmental pollution. Determination of the potential impacts induced by this contamination on key species involved in the equilibrium of ecosystems is therefore a necessity. In this study, we tested the effects of a pyrethroid insecticide, deltamethrin, on the capacity of males from two sympatric Trichogramma species to discriminate the sex pheromones emitted by females of their own species (Trichogramma are parasitoids of Lepidopterous). The impact of an acute exposure as could occur at field edges was evaluated using a dose inducing 20% mortality (LD 20). The impact of a low exposure corresponding to diffuse environmental pollution was evaluated by applying an LD 0.1 (a dose inducing no apparent mortality). For T. semblidis, deltamethrin decreased the specific recognition of sexual pheromones at the higher dose (LD 20) but had no effect on this recognition at the lower dose (LD 0.1). However, deltamethrin decreased the saturation of pheromone receptors at both doses. For T. evanescens, deltamethrin increased the recognition of sexual pheromones at both doses, though not during the same period of observation (at the beginning for the LD 20, at the end for the LD 0.1), but it did not decrease the saturation of the pheromone receptors. These differing results were analyzed considering the behavior of the insects, their level of sensitivity to the insecticide and its mode of action. They provide new insights regarding possible consequences of environmental pollution by insecticides on functional biodiversity.