EFFECT OF AN INSECTICIDE FORMULATION ON Hippodamia convergens (GUÉRIN) AND NYMPHS OF Aphis craccivora (KOCH) IN THE LABORATORY

Abstract

The toxicity of an insecticide formulation containing triazamate and alpha-cypermethrin (120 and 38.4 g L-1, respectively) was evaluated on Hippodamia convergens (Guérin), and its prey, the aphid Aphis craccivora (Koch). Both insects were collected on alfalfa, Medicago sativa L., and reared on faba bean (Vicia faba L.). The formulation was sprayed on alfalfa leaflets in a Potter tower at the maximum dose recommended (400 mL ha-1) and at 50, 25, 15, 10, 5 and 1% of that dose. The eggs and pupae of H. convergens were left on the leaflets after treatment. The mobile stages of both insects were set on the leaflets once they had dried at room temperature to prevent them from escaping. Mortality during the growth stages of H. convergens and adult aphids was evaluated 24 and 48 h after treatment application. The LC50 for both insects was determined by Probit analysis. The maximum dose was moderately toxic (mortality from 80 to 99%) for adults, pupae, and eggs of H. convergens, but toxic (> 99%) for A. craccivora and the ladybird larvae. The LC50s for adults, eggs, larvae, and pupae of H. convergens were 0.405; 341.2; 0.163; and 1.057 mL L-1, respectively, and 0.013 mL L-1 for A. craccivora. The lowest dose (1% of the maximum) caused 93% aphid mortality, indicating that low doses are sufficient to control this pest by spraying. Therefore, the commercial dose could be reduced to this amount and still control A. craccivora, resulting in lesser effects on H. convergens.