Bioactivity of essential oil from leaves of Murraya koenigii against rice weevil, Sitophilus oryzae in stored wheat

The activity of essential oil and powder of curry plant, Murraya koenigii was evaluated as seed protectant of wheat against rice weevil. Preventive fumigation (residual toxicity of organic fumigant) exhibited that inhibition of F1progeny emergence ranged from 32.2 to 62.7% the maximum being observed in 28 days treatment. However, reduction in weight loss was maximum in 5 days treatment. Grain infested for different durations (i.e. 2, 4, 7 and 10 days) and then fumigated with 10μl of curry leaf oil showed significant percent reduction in weight loss of grains in all treatments as compared to control and 4 and 10 day duration exhibited superior results. The mean number of progeny emergence recorded was 24.5, 17.8, 27.5 and 30.8 at 2, 4, 7 and 10 days, respectively and were at par with each other but significantly different from their respective control. Fumigation of seeds freshly infested with three pairs of test insect, with the oil demonstrated good protection of stored wheat as F1progeny emergence, seed damage and per cent weight loss decreased with increase in dose from 1 to 20μl and maximum protection occurred at 20μl. The activity of treated medium (25, 50, 100, 250 and 500 ppm) showed that progeny inhibition was 66.7% at the 500 ppm dose in curry leaf oil. The inhibition of F1 progeny was also observed with leaf powder which shows maximum % progeny inhibition (74.7) and % reduction in weight (60.7) at 500 ppm. It was also found that weight loss of grain decreases with increasing concentration of curry leaf powder.