Efficacy of Chinaberry tree (Meliaceae) aqueous extracts and certain insecticides against the pea leafminer (Diptera : Agromyzidae)

Aqueous extracts of fruits and leaves of the Chinaberry tree, Melia azedara ch L. were tested for their efficacy versus other biotic and synthetic inse cticides against the pea leafminer, Liriomyza huidobrensis (Blanchard). The study included field experiments on naturally infested swiss chard, Beta v ulgaris var. Cicla L., and greenhouse experiments on artificially infested cucumber, Cucumis sativus L. that were conducted in 1995-96. The other trea tments included azadirachtin (0.25 %), ultrafine mineral oil, abamectin, cy romazine, imidacloprid, pyrazophos and control. Results of field experiment s indicated that Melia fruit extract and the other insecticides significant ly lowered the number of larvae per swiss chard plant as compared to the co ntrol, at 5 days sampling after second spray or 15 days after first spray, when two consecutive sprays were performed. However, at 10 days after secon d spray, the fruit extract did not differ significantly from the control, b ut it was comparable in its effect to the insecticides, except abamectin an d cyromazine. In greenhouse experiments, the pea leafminer larvae were foun d at higher densities on cucumber leaves located at the lower plant part (1 0-60 cm) compared to other leaf positions. The Melia fruit extract and the other pesticides significantly decreased the number of live larvae per cucu mber leaf compared to the control, 10 days after each spray. The fruit extr act, abamectin, cyromazine, imidacloprid and pyrazophos lowered the leafmin er population significantly compared to the control, throughout the period of the experiments. However, the fruit extract was significantly less effec tive than these insecticides at the final count, 20 days after second spray . Abamectin and cyromazine consistently showed a significant decrease in nu mber of larvae, in both field and greenhouse experiments. At certain period s of the experiments, Melia extracts were comparable in their efficacy to t he tested commercial biorational and synthetic pesticides. Thus, they have a good potential to be used in the management of the pea leafminer. This is the first report for use of M. azedarach against L. huidobrensis.