Botanicals are promising and attractive alternatives for pest management. In the present study, three botanical oils namely neem (Azadirachta indica), karanja (Pongamia pinnata) and mehogony (Swietenia mahagoni) were tested against the nymphs of Aphis craccivora Koch to evaluate the toxic and repellent effects under laboratory conditions (25 ± 5oC, 65-75% RH). Four concentrations (0.5, 1.0, 1.5, and 2.0%) along with control were maintained with distilled water and tween-20 was used as emulsifier. Leaf dipped method were used for insect bioassay. Insect mortality was recorded at 24, 48 and 72 hours after intervals while repellency was carried out at 2 hours after intervals upto 10th hours and the collected data were analyzed through MSTAT-C program. Results indicated that all the tested oils had toxic and repellent effects against the A. craccivora nymphs. Among the tested botanical oils, no significant difference was observed in terms of mortality over treatment time. But significant difference was noticed over level of concentrations exerted by the botanical oils. The average highest mortality (28.62%) was recorded by the application of mehogony oil whereas neem oil showed the lowest mortality (27.21%) against the A. craccivora and the mortality was directly proportional to the level of concentrations and hour after treatment (HAT). Probit analysis showed the lowest LD50 values of mehogony oil which revealed the highest toxic effect against the nymph of bean aphid. The highest repellent effect (77.33%) was found in mehogony oil (repellent class IV) among all the botanical oils applied. On the contrary, neem (57.33%) and karanja (55.00%) oils belonged to the same repellent class that is repellent class II. Although all the tested botanical oils evaluated showed toxic and repellent effects but mehogony oil performed as the best potent oil against the nymphs. We therefore suggested using the mehogony oil for the management of bean aphid. SAARC J. Agric., 19(1): 139-154 (2021)

Results of the evaluation on bioefficacy of three indigenous plant extracts for toxicity and residual effects against the pulse beetle, Callosobruchus chinensis L. (Bruchidae: Coleoptera) showed that the plant extracts had toxic and residual effects for controlling pulse beetle. Mortality and residual effects were statistically different among the plant extracts and doses applied. Neem extract showed the highest adult mortality (36.78%) whereas eucalyptus extract showed the lowest (22.75%). The order of the toxicity of three plant extracts was found as neem > custard apple > eucalyptus. Mortality was found directly proportional to the hour after treatments which increased with the progress of time. Between two solvents, acetone solvent possessed the highest toxicity (mortality 32.95%) but methanol showed the lowest toxicity (mortality 30.56%). The residual toxicity was evaluated on the basis of egg laid, adult emergence, seed infestation and weight loss caused by the insect. The highest residual toxicity was found in neem extract with acetone while the lowest in eucalyptus extract with acetone. Neem extract with acetone and custard apple extract with methanol solvent were found effective to toxic and residual effects against pulse beetle of three plant extracts applied. Asiat. Soc. Bangladesh, Sci. 46(1): 1-12, June 2020

The two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) is a cosmopolitan pest that causes considerable damage to vegetables, fruit and flower plants. The acaricidal, ovicidal and repellent activity of four different extracts of Aloe vera L. (Asphodelaceae) leaves were evaluated against T. urticae under laboratory conditions. Four different solvents of A. vera leaf extracts were tested against T. urticae at concentrations of 0.25, 0.50, 1.0 and 2.0%. The results indicated that all extracts had lethal and repellent effects on T. urticae. The acetone extract showed the highest mortality (95.0%) of adult females followed by ethanol (83.0%) at 2.0% concentration. The LC50 values of acetone, ethanol, methanol and petroleum ether extract for adult females were 0.446, 0.667, 0.953 and 1.279, respectively and for eggs were 0.950, 1.406, 2.115 and 3.312, respectively. The ethanol extract was found to be more effective as a repellent against adult females of T. urticae followed by acetone, methanol and petroleum ether causing a reduction in egg production per female by 96.0, 94.0, 85.0 and 83.0%, respectively. In the residual test, the acetone extract showed the highest mortality (49%) after 1 hour of treatment followed by ethanol (43.0%), methanol (29.0%) and petroleum ether (25.0%). The percent of mortality decreased after 48 and 72 hours after treatments. The results show that A. vera has a high potential to become a botanical acaricide for controlling T. urticae.