Toxicity of certain insecticides to predatory beetle Hippodamia variegata

Abstract: Hippodamia variegata is the most common and the dominant predator in Iran. Theinsect is the key predator of the aphids occurring on vegetables crops. In search of the least toxicinsecticide to this predator, we have investigated the toxicity of four commonly used pesticides inthe laboratory. The insecticides were Confidor SC 35 (imidacloprid), Chess WP 25(pymetrozine), Vertimec EC 1.8 (abamectin) and insecticide soap WSC 65 (cocamide DEA). Thetest was carried out in transparent plastic tubes (7.5cm in diameter and 3.5cm in height) coveredwith glass plates (10×10cm) at the top and the bottom. Tow 1-cm2 holes were cut in the tube forventilation. Adults of H. variegata were exposed to the residues of pesticides on glass plates for72 hours. The predators were fed with black bean aphids (Aphis fabae) during the test period.Imidacloprid was the most toxic (LC50 = 0.04g/l) and all insects were dead by this insecticide at20% of recommended dose (0.4ml/l). Abamectin (LC50 = 0.28g/l) was the next followed bypymetrozine (LC50 = 0.72g/l). DEA cocamide did not cause any mortality even at recommendeddose (1.5-2.0ml/l).