EFFECT OF NEEM OIL AND NEEM LEAF EXTRACT ON MORTALITY, GROWTH AND FEEDING RESPONSES OF JUTE HAIRY CATERPILLAR, Spilarctia obliqua (Walker)

Abstract

Experiments were conducted in the I)ivision of Entomology. Bangladesh Jute Research Institute, Manik Mia Avenue. Dhaka. to study the clTbct of Neem oil and Neem leaf extract on mortality, growth and feeding responses ofjute haiiy caterpillar. Spilarctia obliqua (Walker). To evaluate the efficacy or neem products on the larval mortal fly. third. Iourth and ti (lii instar larvae were allowed to feed on jute leaves treated with neem extract (1:20) and nccm oil at 0.5. 1.0. 2.5 and 5.0% emulsified with 0.1% Nikalin and their modality were recorded at different days after treatment. Maximum percent larval mortality occurred at the higher two concentratiOns (2.5 and 5.0%) in each instar. Neem lealextract (1:20) and lower concentratIons (0.5 and 1.0%) of neeni oil. signiticantly increased the larval mortality. flue median lethal dose (11)50) values of neem oil for different larval instars at above concentration were also determined. The effect of neem oil on growth and feeding respohises were evaluated by exposing fourth instar larvae to lOad treated with riccni oil at 0.5% concentration either for 48 hours (48 hrs treatment) or continuously throughout the larval period (continuous trcatment).Neeni oil exhibited growth inhibiting etiCets on the developing larvae and reduced the food consumption as compared to control. Ilie effects were more pronounced in continuous treatment. Such efiCets on development were prolongation of larval period. reduction in the larval size, blackish spots on the larval body. hairless larvae and development of abnonnal pupae. Adults developed from treated larvae were malformed or had crippled wings. Neem served as a potential growth inhibitor and feeding deterrent against S. ohl:qua and it can be integrated with appropriate cultural and biological pest control tactics.