Sublethal effects from endosulfan on parasitization by the parasitoid wasp Leptopilina boulardi and specificity of nervous pathways involved.

BACKGROUND: Endosulfan is a semi-permanent pollutant that can be transported long distances through the atmosphere. Although phased out in many countries, it is still used in some populated areas and thus largely contributes to environmental pollution. It can impact non-target species such as Leptopilina boulardi, a hymenopteran parasitoid that is a beneficial insect because it controls the populations of its host. Only one L. boulardi egg can successfully develop in its host, a Drosophila larva. As a consequence, parasitoid females generally lay only one egg per host, except when they are infected by a virus (LbFV) that triggers a superparasitization behavior (laying more than one egg per host). The effects of an LC20 of endosulfan on the parasitization behavior of two L. boulardi strains, one infected by LbFV and the other not, were evaluated.

RESULTS: The insecticide decreased the number of host larvae parasitized by both strains (decreased rate of parasitization) but had no impact on the number of eggs laid per host (i.e., the rate of superparasitization) whether or not the strain was infected by LbFV.

CONCLUSIONS: Recent research1 has shown that the organophosphorus insecticide chlorpyrifos induced superparasitization in parasitoid females. Both endosulfan and chlorpyrifos are neurotoxic and induce nervous system hyperstimulation. The fact that endosulfan does not trigger superparasitization whereas chlorpyrifos does suggests that this effect is due to the specific pathway impacted by chlorpyrifos, the cholinergic nervous pathway. The consequences of these results in the context of awareness of environmental pollution by pesticides are discussed. This article is protected by copyright. All rights reserved.