Efficacy of Some Vegetable Oils Against Pulse Beetle, Callosobruchus chinensis (Linn.) on Cowpea, Vigna unguiculata (L.)

Six vegetable oils viz., castor (Ricinus communis L.), mustard (Brassica juncea L.), groundnut (Arachis hypogaea L.), sesamum (Sesamum indicum L), coconut (Cocos nucifera L.) and sunflower (Helianthus annus L.) were tested against Callosobruchus chinensis (Linn.) in cowpea. All the oils caused significant mortality in adults after three days treatment. The castor oil at 1.0 ml/100 g seeds was found to be the most effective causing 80.7 per cent mortality of adults. The mean mortality varied from 60.0 to 80.2 per cent in different oils at the highest dose level of 1.0 ml/100 g seeds. Castor oil @ 1.0 ml/100 g seeds was the most effective in inhibiting the oviposition (26.6 eggs/female) as against 79.4 eggs/female in untreated seeds. At 1.0 ml/100 g seeds, castor oil caused maximum reduction in egg viability (61.7%) followed by mustard oil (56.7%). The longevity of male and female adults decreased with the increase in doses of oils. The treatment of castor oil @ 1.0 ml/100 g seeds caused maximum reduction in adult emergence in F₁ generation (85.0%) followed by mustard oil (83.7%), groundnut oil (73.3%). No adverse effect of tested oils was observed on the germination of cowpea seeds upto 150 days of treatment.