Evaluation of Plant Powders and Cooking Oils against Maize Weevil, Sitophilus zeamais M. (Coleopteran: Curculionidae) under Laboratory Conditions

Abstract

t In storage, maize grains are severely destroyed by insects and other storage pests. One of the primary causes of grain loss in stored maize is the damage caused by maize weevil, Sitophilus zeamais. A study was conducted to evaluate selected locally available botanical powders and cooking oils for their effectiveness as grain protectants against maize weevils at JUCAVM in year 2011. The plant powders and cooking oils were compared with untreated control and Malathion super dust as standard check. The experiment was laid-out in Completely Randomized Design with 13 treatments each replicated thrice. Different dependent variables such as cumulative adult mortality, F1 progeny emergency, grain damage were assessed. The results revealed that, among the botanical powders, there was an increased cumulative adult S. zeamais mortality, i.e. higher mortality, from powders of Chenopodium ambrosoides (70% with LT50 of 6.50 days), Azadiricta indica leaf (70% with LT50 of 6.00 days), A. indica bark (70% with LT50 of 8.40 days) and Tagetus erecta (70% with LT50 of 9.20 days) after 20 days of exposure periods. Apart from the untreated control, low mortality of S. zeamais adult was recorded from Allium sativum (50% with LT50 of 18.01 days), C. citratus (55% with LT50 of 18.30 days), Maesa lanceolata (55% with LT50 of 16.20 days) and Echinops kebericho (55% with LT50 of 14.50 days) after 20 days of exposure periods. Highest S. zeamais adult mortality of 95%, 100% and 100% was recorded from Brassica carinata oil, Gossypium hirsutum oil and the standard chemical Malathion, respectively with LT50 of less than one day in all cases. Maximum number of progeny was emerged from untreated check from 25th~40th days of exposures with cumulative increase (2 to 14 adults). There was no F1 progeny emergency from the three treatments (oils and Malathion) over the exposure periods reassuring the potency of the cooking oils against S. zeamais. As a result there was no perforated seed; no weight loss and maximum germination percentage of 94.60% were registered from the two cooking oils on par with the Malathion (95.50%). In conclusion, the two cooking oils were found to be the most potent bio-insecticides on par with standard check, Malathion and they can be used in integrated management of maize weevil, S. zeamais