INSECTICIDAL ACTIVITY OF MELIACEOUS SEED EXTRACTS AGAINST Crocidolomia binotalis ZELLER (LEPIDOPTERA: PYRALIDAE)
Acetone seed extracts of 21 species of Meliaceae wel:e evaluated for their insecticidal activity against second-instar larvae of Crocidolomia binotalis Zeller by a leaf-residue feeding method. The larvae were fed extract-treated broccoli leaves for 2 days. then were maintained on untreated leaves until the fourth-ins tar stage. Records were kept in regard to the area of leaves eaten during the 2-day feeding treatment, daily larval mortality, and developmental time of surviving larvae from instar II to ins tar IV. The seed extracts of Aglaia harmsiana, Azadirachta indica (neem) and Dysoxylum mollissimum at a concentration of 0.25% exhibited a strong insecticidal activity against C. binotalis larvae (95-100% mortality), those of Aglaia odoratissima and Trichilia trijuga showed a fairly strong activity (78% and 87% mortality), whereas the activity of other extracts varied from inactive to moderately active (0 - 73% mortality). The active extracts generally exhibited the three kinds of effects, i. e. antijeedant, insecticidal and developmental derangement, at similar levels. The active extracts at 0.25% inhibited feeding by C. binotalis larvae on treated leaves by 78.4 - 96.6% and prolonged the developmental time from instar II to instar IV by 2.2 - 4.2 days as compared with controls. Further studies are needed to identifY insecticidal compounds in the said active extracts, except neem which has been exhaustively studied.