Concentration-mortality responses of Myzus persicae and natural enemies to selected insecticides.

The toxicity of six insecticides was determined for the peach-potato aphid, Myzus persicae (Hemiptera: Aphididae), and some of its natural enemies - the predatory beetles Cycloneda sanguinea (Coccinellidae) and Acanthinus sp. (Anthicidae), and the wasp parasitoid Diaeretiella rapae (Aphidiidae). Natural enemies from these groups are important natural biological control agents in a number of agroecosystems, and insecticides potentially safe to these non-target organisms should be identified using standardized tests. Thus, concentration-mortality bioassays were carried out with both the aphid and its natural enemies to assess the toxicity and selectivity of acephate, deltamethrin, dimethoate, methamidophos, methyl parathion, and pirimicarb. The latter insecticide was highly selective to all natural enemies tested, and its LC(90) for M. persicae was 14-fold lower than the field rate recommended for control of the aphid in brassica crops. Methyl parathion also showed selectivity to C. sanguinea and Acanthinus sp., but not to D. rapae. Acephate was the least potent insecticide against M. persicae and was equally or more toxic to the natural enemies relative to the aphid. Pirimicarb and methyl parathion were efficient against M. persicae and selective in favor of two of the natural enemies tested. Acanthinus sp. and C. sanguinea were more tolerant to the insecticides than was the parasitoid D. rapae. This study shows that there are selective insecticides that may be compatible with conservation of natural enemies in brassica crops, which is important practical information to improve integrated pest management systems in these crops.