Sensitivity and accuracy of a bio-assay for the determination of the concentration of residual pesticide in natural water bodies.

Determination of pesticide levels in natural water bodies requires complex chemical methods not always available in tropical countries where such control programmes are implemented. Apart from chemical methods, effectiveness of treatment can be estimated by mortality of target and non-target species. But the latter criteria do not permit a good appraisal of dispersion and residual activity of pesticide. We propose here a simple and cheap bio-assay adaptable to water-borne vector or intermediate host control programmes. Results obtained with the bio-assay were compared with those obtained with gas liquid chromatography, a standard chemical method.