COMPARATIVE EFFICACY OF NEEM (Azadirachta indica L.)AND PEPPERMINT (Mentha piperita L.) LEAF POWDERS AS A CONTROL OF ADULT MAIZE WEEVIL (Sitophilus zeamais Motsch) IN STORED SORGHUM GRAINS

Abstract

Plant extracts in powder or essential oil form from different bioactive compound producing plants are known to be effective repellents and insecticides against different storage pests of grains. Post-harvest losses are one of the major causes of food insecurity in the developing world. , the present study was planned to investigate the effect of neem and peppermint leaf powders in control of maize weevil and the prolonged storage of the powders on their insecticidal activity. A 2 × 2 x 3 factorial experiment was laid in a Complete Randomized Design (CRD) with two replications. The results indicated that all the treatments had shown high repellence against maize weevil at all amounts used (0.5, 1, and 1.5 grams) for the whole duration storage. However, there was no significant difference among 0.5, 1, and 1.5 grams for all the treatments including neem, mint, and combination of neem and mint powders. Mean separation for maize weevil mortality rate during 48 days of treatment of sorghum grain with different amounts of neem, mint and combination of neem and mint leaf powder had shown that there was no mortality of maize weevils recorded for control (0gram). However, significant mortality was recorded for each treatment during 45 days of storage. The highest mean mortality rate was recorded for neem leaf powder than for mint leaf powder, and combinations of neem and mint leaf powders showing insecticidal property of neem leaves. Maize weevil progeny emergence rate during extended duration of sorghum grain storage as treated by neem, mint, and combinations of neem-mint leaf powders indicated that the highest progeny emergence rate was recorded for control group in all treatments. Only after 48 days was the progeny emergence recorded for experimental groups. It can be concluded from the present study that neem and mint leaf powders could be used as effective insect repellents. Even though the neem and mint leaf powder retards population growth of maize weevil, the powders cannot be recommended for extended storage duration.