Abstract:

The biology of the maize weevil, S. zeamais, was studied on maize grains. Incubation period of the egg was observed to range from 4-6 days with an average of 5 days. The larval period was found to range from 25-31 days with an average of 29 days and pupa took an average of 8.2 days to develop into an adult. The average developmental period of the weevil was found to be 41 days. Amongst different plant powders, Lantana powder proved to be most effective followed by Melia leaf powder @ 5g/100g grain. Highest adult cumulative mortality (100 %) was observed in grains treated with Lantana powder and the least mortality was obtained in Tulsi treated grains. The lowest grain damage (4.40 %) was recorded in maize grains treated with Lantana leaf powder treatment and was at par with Melia treated (5.27 %). The highest weight loss was recorded in Tulsi leaf powder (6.19 %) which was statistically at par with eupatorium treated grains (5.70 %). All the plant powders were found superior over control. In the treatment of maize grains with different botanical oils, Neem oil proved to be most effective at both the doses (1ml and 3ml/kg grain). 100 % mortality was obtained in grains treated vvith Neem and Mustard oils @ 3ml/kg grains. There was no weight loss and grain damage in treatment with Neem oils @ 3ml/kg grain and adult emergence was found to be completely inhibited. Lowest weight loss (0. 22 %) was observed in maize grains treated with Mustard oil, followed by Soybean oil (0.75 %). Highest weight loss (2.27 %) was obtained in maize grains treated with Coconut oil. Highest grain damage of (6.38 %) was obtained in maize grains treated with Soybean oil and lowest damage (1.79 %) in mustard oil treated grains. The treatment with oils had no adverse effect on the germination of the grains.