Residual toxicity of some insecticides on the predatory bugs Dicyphus tamaninii and Macrolophus caliginosus

Chlorpyrifos, formetanate, methamidophos, imidacloprid and endosulfan were tested in the laboratory for their effects upon the mirid bugs Dicyphus tam aninii and Macrolophus caliginosus, which are polyphagous predators used fo r IPM programs in some vegetable crops. The mortality of third-fourth insta r nymphs was checked 24 and 48 hours and 7 days after exposure to 1-, 3-, 8 -, 21- and 30-day residues of the treatments on tomato leaflets. The reprod uctive capacity of surviving females also was evaluated for 15 days and com pared with females that had not been exposed to insecticides. Chlorpyrifos, formetanate and methamidophos are considered persistent because they remai ned toxic to both mirid species for 30 days. Imidacloprid is moderately per sistent, becoming harmless by 21 days after treatment for M. caliginosus an d by 30 days after treatment for D. tamaninii. Endosulfan is moderately per sistent for M. caliginosus, becoming harmless by 21 days after treatment, a nd is short lived for D. tamaninii, becoming harmless by 3 days after treat ment. There were no effects on the reproductive capacity of females that we re exposed as nymphs to the insecticides tested. Of all the insecticides, o nly endosulfan is marginally compatible with the use of D. tamaninii.