Evaluation of Insecticidal Efficacy of Two Leaf Powders for Control of Khapra Beetle, Trogoderma granarium (Everts) (Coleoptera: Dermestidae) in Wheat Grains

Experiment was conducted to evaluate the efficacy of leaf powders of Senna mimosoides and Datura alba for the control of khapra beetle, Trogoderma granarium on stored wheat grains. Twenty 0-3 days old unsexed adults of T. granarium were introduced into each cup containing 20g of grains and covered with muslin cloth to allow aeration and prevent exit or entry of insects. The powders were applied at 5, 10 and 15% concentrations to study mortality, repellency and seed weight loss. The experiment were laid out in a Completely Randomized Design (CRD) of 5 by 4 (5 treatments and 4 replicates) including standard and experimental controls under laboratory conditions (28±2oC; 74±5% RH) for 28 days. Data obtained were analyzed using Analysis of Variance and means were separated using Turkey’s post hoc test. Both powders showed the presence of alkaloids, saponins, cardiac glycosides, flavonoids, phenols and tannins to which insecticidal properties can be attributed against T. granarium. There was an increase in mortality with the days of exposure in all concentrations with leaf extract of i + D. alba being more effective at 15% (1.25± 0.50) when compared with the control. Also, the powders of S. mimosoides + D. alba at various concentrations exhibited the highest repellency (90%) activity followed by those of S. mimosoides and D. alba separately. The seeds treated with cocktail of the powders gave the lowest seed damage, followed by that of S. mimosoides and D. alba when compared to the experimental control. The results indicated that powders used as sole or cocktail significantly (p<0.05) reduced insect populations and offered greater protection and high repellency compared to the control. Since S. mimosoides and D. alba powders are affordable for small farmers and environmentally safe, they ought to be promoted for use against khapra beetles. This is because they can be used as an alternative to synthetic pesticides in integrated pest management.