Experimental bases for a chemical control of Coquillettidia mosquito populations

Abstract

Coquillettidia mosquitoes are not efficiently controlled by the conventional chemical practices which are known to be satisfactory against the larvae of other mosquito species. A research project was undertaken to conceive a new management strategy using plants as pesticide vectors to reach the Coquillettidia aquatic larvae. Therefore, larval mortality was measured in the presence of plants treated with phloem-translocated pesticides. The herbicide glyphosate at sub-lethal concentrations induced root epidermal cell lyses in maize plantlets cultivated in aqueous media, which clearly decreased larval fixation. Therefore, such herbicide strategy might operate through disturbing the larval physiological activities depending on fixation. The dimethoate insecticide did not affect root viability but at low concentrations seemed to disturb the plant–insect interactions. Larvae showed a lower attraction for roots and a considerable decrease in the root fixation rate. These larval behavior modifications were sufficient to induce mortality, probably due to a lack of fixation on plant roots. The effectiveness of plant foliar treatment with glyphosate or dimethoate under laboratory conditions suggested that it might be the basis for an efficient control strategy for Coquillettidia larvae and mosquitoes having the same living conditions in ponds and for which fixation on macrophyte roots is an absolute requirement ( e.g. Mansonia, Mimomyia).