Efficacy of Leaf Powders of Senna obtusifolia (L.) and Mitracarpus hirtus (L.) DC. on the Survival of Sitophilus zeamais Motschulsky [Coleoptera: Curculionidae] on Sorghum Grains During Storage

Experiments were conducted in the Biology Laboratory 1 of the Department of Biology of Umaru Musa Yar'adua University (UMYU), Katsina to test the insecticidal effects of leaf powders of Senna obtusifolia (L.) and Mitracarpus hirtus (L.) DC. Doses of 1.0, 2.0 3.0g of each of the leaf powders and 1.0g of Pestox (R) (cypermethrin) were applied to 50g each of sorghum grains in which five pairs of adult Sitophilus zeamais Motschulsky were released for adult mortality, emergence and grain damage tests. The results showed that the highest (36.67%) mortality of S. zeamais obtained when 3.0g of S. obtusifolia was applied while the least (10.00%) was recorded from the treatments of 1.0g M. hirtus. The findings of this study also showed that adult mortality of S. zeamais was directly proportional to the amounts of the leaf powders applied. The results also revealed that from the highest (114.33) adult emergence of the weevils was obtained when 1.0g of M. hirtus was applied, while the least (40.67) was recorded from the treatment of 3.0g S. obtusifolia. The findings of this study showed that the adult emergence of S. zeamais was inversely proportional to the amounts of the leaf powders applied. Generally, the efficacy of the leaf powders on the survival of S. zeamais was found to be significantly (p<0.05) different between the test powders and the control. Findings of this study showed that the leaf powders of S. obtusifolia and M. hirtus were effective in protecting sorghum grains against S. zeamais infestation in stores. Therefore, more research is recommended on toxicity effect of these plant powders on other insect pests.