Phytotoxicity of leaf extracts of multipurpose trees against insect pests in bitter gourd (Momordica charantia) and brinjal (Solanum melongena)

Field studies were conducted to assess the allelopathic influence of leaf extract of multipurpose trees viz., Ailanthus (Ailanthus triphysa Dennst.), cashew (Anacardium occidentale L.), Casuarina (Casuarina equisettifolia L), gliricidia (Gliricidia sepium Steud.), jack (Artocarpus heterophyllus Lam.), Strychnos (Strychnos nux-vomica L.), mango (Mangifera indica L.), portia (Thespesia populnea (L.) Soland.), tamarind (Tamarindus indicus L.), teak (Tectona grandis L.F.), grown in multi-storey home gardens of Kerala, India on growth, yield and insect pests in vegetables viz., bitter gourd (Momordica charantia L. cv. Preethi) and brinjal (Solanum melongena L. cv. Haritha). Spraying with Ailanthus and cashew leaf extracts was as effective as insecticides in reducing fruit fly (Daucus cucurbitae) attack in bitter gourd and yield obtained was also identical to insecticides treatment. Ailanthus, cashew, tamarind and teak effectively controlled epilachna beetle (Epilachna vigintiopunctata). Insect control achieved by spraying tamarind and teak leaf extracts treatments was similar to insecticide spraying. In brinjal, extracts of Ailanthus, cashew and casuarina reduced fruit borer infestation (Leucinodes orbonalis) considerably. Ailanthus and cashew extracts also improved the yield and was on par with that obtained with spraying of insecticides. The leaf extract of the trees were analyzed by Thin Layer Chromatography (TLC) for the presence of five important groups of secondary metabolites viz., terpenoids, alkaloids, flavonoids, saponins and triterpenes. The results show the possible use of leaf extracts of Ailanthus and cashew, to control the insect pests in bitter gourd and brinjal.