Evaluation of some essential oils against maize weevil Sitophilus zeamais (L.)

Maize is the most important cereal in Africa, and in Ethiopia, it is the second widely grown cereal. Post harvest losses due to the maize weevil Sitophilus zeamais is an important constraint, with grain losses ranging from 20–90%. This study evaluates the efficacy of essential oils against this weevil as an alternative to pesticides. Adult S. zeamais were bred in jars in the laboratory at 60–65% RH and 27±2°C. Five treatments viz., eucalyptuss, citronella grass and lemon grass essential oils each at 2.5, 5.0, 7.5 and 10.0/were poured into petri dishes containing diatomaceous earth (DE). Ethiolathion (Malathion 5%) and 95% ethanol were used as a standard check and as control, respectively. Ten pairs of adults S. zeamais were introduced into each treatment containing maize grains. Treatments were arranged in a complete randomized design (CRD) with four replications. The numbers of dead insects in each petri dish were counted at 24h, 48h, 72h, 96h, and 120h to estimate mortality rate. Grain weight losses were determined after seven days. The results revealed significant differences among treatments effects in the rate of mortality. All essential oil significantly affected weevil mortality compared to untreated control. The results showed that grain weight loss can be 18–60% after seven day due to weevil damage.