No abstract

Eighteen spices were screened for their insecticidal potential and antiovipositional properties against the rice weevil-Sitophilus oryzae-a serious insect pest of stored food grains. The bioefficacy of the powders and hexane extracts of selected spices were determined by assessing the toxicity, effect on F 1 progeny, contact toxicity, persistence and seed viability. Responses varied with the spices, dosage and exposure time. Powders of mace and pepper, at 1% level were highly effective resulting in total mortality of S. oryzae by one week followed by nutmeg and clove with 100% mortality and cinnamon and star anise with 90% mortality at 5% concentration. These spices also completely inhibited F 1 progeny. The hexane extracts of these spices at 1,000 ppm showed insecticidal activity, with pepper extract recording 100% mortality by 5 days. S. oryzae was susceptible to clove oil resulting in 92% mortality. Mortality was 51.63% in nutmeg, 66.6% in cinnamon, and 79.8% in case of mace and star anise. Hexane extracts of star anise, cinnamon and clove at 0.59 μl/cm 2 on filter paper discs induced 100% mortality by 72 h. These spices offered protection to wheat up to 9 months without affecting seed germination thereby showing promise as grain protectants.

No abstract

In the present investigation, essential oil (EO) of Ocimum tenuiflorum and its principal constituent (eugenol) was evaluated for its toxicity and mode of action against Callosobruchus maculatus. Furthermore, fumigant toxicity and germination studies on the application of O. tenuiflorum EO and eugenol against C. maculatus on different pulses was also studied. Fumigant activity studies revealed that EO toxicity was significantly (p \ 0.05) influenced by concentration and exposure time. In fumigant toxicity assay without food, O. tenuiflorum EO and eugenol showed LC 50 value of 278.6 and 256.5 lL/L air, respectively, at one hour exposure. Further, O. tenuiflorum EO displayed fumigant toxicity via inhibiting acetylcholinesterase activity. Pulses treated with O. tenuiflorum EO showed 70% of C. maculatus mortality at 250 lL/L air concentration after 24 h. Furthermore, these treatments didn't affect the seed viability of the pulses tested. Hence, the application of O. tenuiflorum EO has potential scope as a botanical insecticide.