Antifeedant activity of Melia azedarach (L.) extracts to Diabrotica speciosa (Genn.) (Coleoptera : Chrysomelidae) beetles

Studies were carried out to determine the antifeedant activity of extracts of leaves, stems flowers and fruits of Melia azedarach (L.), the dosage act ivity responses to the most active extract and the effects of sunlight in t he activity persistence to Diabrotica speciosa (Genn.) beetles. Extracts ef ficiency was determined by evaluating leaf consumption. Insect feeding was deterred by stems, fruits and flowers extracts. Flowers and fruits extracts were the most efficient. Stems extract was in an intermediate position bet ween the two most efficient and the least one (leaf extracts). The most act ive extract (flowers) was sprayed at concentrations of 0, 1, 2, 3, 4, 5, 6 and 7 g/100 mi. Feeding of D. speciosa on common bean leaves extracts decre ased significantly with increasing concentrations of flowers extract, respo nding in a concentration-dependent manner. Two days after spraying, from 4 to 7 g/100 mi concentrations, feeding was totally inhibited. Four days afte r spraying, feeding occurred in 4-g/100 mi concentration. When common bean plants exposed to sunlight were sprayed with flowers extract (5-g/100 mi), beetles feeding increased gradually after extract spraying. Results showed that the lack of activity under sunlight conditions was a great limitation to use M. azedarach aqueous extracts.