The study was carried out to assess the larvicidal efficacies of some indigenous plant seed extracts against epilachna beetle, Epilachna vigintioctopunctata in the laboratory of the Department of Entomology, HSTU, Dinajpur, Bangladesh. Petroleum ether and methanol solvent extracts of ata (Annona squamosa), neem (Azadirachta indica), dhutura (Datura metel) and castor (Ricinus communis) seeds were evaluated for their larvicidal properties against the larval stage of E. vigintioctopunctata. The result revealed that all the tested plant extracts had more or less insecticidal effect against the larvae and their progeny. Among the plant extracts, ata seed extract in methanol solvent performed the highest toxicity (LD 50 value 0.031 mg/insect) in larval stage after 72 hours exposure time. The effects of the extracts on fecundity, fertility and F 1 adult emergence of the epilachna beetle at doses 4.0, 2.0 and 1.0 ml/l of water including untreated control were also evaluated. The result indicated that, among the extracts, ata seed extract at maximum dose (4.0 ml/l water) showed the highest efficacy with the inhibition of total eggs (74.1%), viable eggs (80.4%) and number of emergent adult progeny (87.3%). The result also revealed that the number of eggs, number of viable eggs and F 1 progeny production decreased with the increase of doses. All the treated doses effectively reduced the epilachna beetle as compared to untreated control.

Context: Insect bio assay and repellency test can play a vital role in special environmental conditions. Objectives: To screen out the insecticidal potency of some plant extracts to control the adult lesser grain borer by insect bioassay and repellency tests. Materials and Methods: Toxicity test of five indigenous plant extracts with three concentrations were conducted against Rhizopertha dominica. Insect mortality was recorded at 24, 48, and 72 HAT. For residual toxicity test, insect mortality was recorded at 1, 2, 7, 15 and 21 DAT. The repellent activities were evaluated using the filter paper impregnation method and the data were counted at hourly intervals up to 6 th hour. In all cases ten insects per replication were tested and each treatment was replicated thrice. The collected data were statistically analyzed. Results: Among the tested plant extracts, neem showed the highest toxic and repellent effects against the lesser grain borer. All the doses applied had direct toxicity, residual and repellency effects while 8% dose showed the highest response. The order of toxicity was found as neem > biskatali > karabi > akanda > ata. Mortality percentages were directly proportional to the time after treatment. Conclusion: This study proved that the leaf extract of indigenous plants like neem, biskatali, karabi ata and akanda can be used to protect stored grain pests.