SUBLETHAL EFFECTS OF THE INSECTICIDE CHLORPYRIFOS ON THE SEX PHEROMONAL COMMUNICATION OF TRICHOGRAMMA-BRASSICAE

Environmental pollution by insecticides is now a great concern. Even i f they do not provoke any mortality, sublethal doses may be an importa nt threat for species and population equilibriums by modifying physiol ogical or behavioral parameters like pheromonal communications. This i s specially true for species in strong interaction like parasitoids an d hosts. In this work, we determined the effects of an LD 0.1 of chlor pyrifos (organophosphorus insecticide), a dose that does not cause any apparent mortality (theoretically 0.1% of mortality), on sex pheromon al communication. We found that, when males are submitted to the insec ticide, their response to the female pheromone is very significantly d ecreased. On the other hand, when females are submitted to the insecti cide, the response of males to the pheromone is slightly but significa ntly increased. These results can be explained by the effect of the in secticide on nervous transmissions. Perturbation by the chlorpyrifos o f 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 co ntrol of Lepidopterus pest, pollution of the environment by this insec ticide could lead to a global modification of the biodiversity. (C) 19 98 Elsevier Science Ltd.