Toxicity of a Neem (Azadirachta indica) insecticide to certain aquatic organisms.

Neem based insecticides are likely to show a large increase in use in the near future. In the present work, the toxicity of a neem insecticide, Neem-Azal-T/S, was tested against the mosquito larvae, as well as against certain non target organisms occurring in a polluted pond and a shallow stream, located in a cultivated area in Giza, Egypt. Samples of water containing the experimental animals were collected from this area, and toxicity tests were conducted in the laboratory by exposing them to a series of concentrations of the botanical insecticide, using the water of the pond and stream at room temperature (28-31 degrees C). The compound was more or less toxic to all the tested species. The LC50S and mortality rates were determined. The order of tolerance of the organisms to different concentrations of the insecticide was: larvae of Bufo regularis (Amphibia) > Aedes caspius. (Insecta) > Gambusia affinis (Poeciliidae) > Cyclops sp. > Daphnia magna (Crustacea). At a concentration of 20 ppm, all the tadpoles died within 9 days, while all other individuals died within 5 to 8 days after exposure to a concentration of 10 ppm of Neem Azal insecticide.