Sublethal effects of the insecticide chlorpyrifos on the sex pheromonal communication of Trichogramma brassicae

Environmental pollution by insecticides is now a great concern. Even if they do not provoke any mortality, sublethal doses may be an important threat for species and population equilibriums by modifying physiological or behavioral parameters like pheromonal communications. This is specially true for species in strong interaction like parasitoids and hosts. In this work, we determined the effects of an LD 0.1 of chlorpyrifos (organophosphorus insecticide), a dose that does not cause any apparent mortality (theoretically 0.1% of mortality), on sex pheromonal communication. We found that, when males are submitted to the insecticide, their response to the female pheromone is very significantly decreased. On the other hand, when females are submitted to the insecticide, the response of males to the pheromone is slightly but significantly increased. These results can be explained by the effect of the insecticide on nervous transmissions. Perturbation by the chlorpyrifos of pheromonal communication of Trichogramma may endanger this species. A decrease of the fecundation of females would provoke an increase in male progeny (arrhenotocus species) and therefore modify the sex ratio of these populations. As Trichogramma populations intervene in the control of Lepidopterus pest, pollution of the environment by this insecticide could lead to a global modification of the biodiversity. (C) 1998 Elsevier Science Ltd.