Efficacy Of Azadirachta Indica-Treated Storage Materials Against Maize Weevil Sitophilus Zeamais And Rice Weevil Sitophilus Oryzae

Abstract

Weevil infestations cause post-harvest losses and have become important constraints to storage entomology and food security in Nigeria. The present study is aimed at assessing the efficacy of Azadirachta indica-treated storage materials against Sitophilus zeamais and Sitophilus oryzae. Storage materials such as bagco bags, calico bags, and plastic containers were treated with different concentrations (0.5, 1.0, and 1.5mg/ml) of A. indica oil. Untreated storage materials served as the control. These treatments were replicated three times following a completely randomized design in the laboratory and monitored for 100 days. The results showed a significant decrease (p<0.05) in weight loss of infested maize and rice grains with different concentrations of the extract and with the different storage materials compared to the control. The highest weight loss among the treatment concentrations across all the storage materials treated with Azadirachta indica was recorded for rice grains stored in calico bags at 0.5mg/ml with mean value of 10.61±0.37 and7.12±1.41 for maize grains, while the least value of 1.14±0.09 was recorded for rice grains stored in plastic containers at 1.5mg/ml and 0.75±0.21 was recorded for maize grains stored in plastic containers at 1.5mg/ml. there was a significant increase (p<0.05) in mortality of S. zeamais and S. oryzae with increased concentrations of the extracts compared to the control. There was no significant increase in mortality of S. zeamais and S. oryzae compared with the storage materials. The highest mortality for S. oryzae 8.00±0.58 was seen in rice grains stored in plastic containers at 0.5mg/ml concentration and least mortality 4.00±0.58 was seen in those stored in bagco bag at 1.0mg/ml concentration. For S. zeamais, there was no significant increase on the mortality of S. oryzae between 0.5mg/ml and 1.0mg/ml concentrations in A. indica treated bagco bags and between 1.0mg/ml and 1.5mg/ml concentrations in A. indica treated plastic containers. S. oryzae in maize grains stored in plastic containers at 1.0mg/ml had the highest mortality 9.00±1.53 and the least mortality (3.00±0.00) was recorded for S. zeamais in maize grains stored in calico bag at 0.5mg/ml of A. indica treated materials. Results of the storage materials (Bagco bag, Calico bag, and Plastic container) treated with Azadirachta indica leaves extract showed significant decrease (p<0.05) in adult emergence of S. zeamais and S. oryzae in the different concentrations of extracts compared to the control. There was no significant decrease among the A. indica treated storage materials for S. zeamais and S. oryzae emergence. The highest S.oryzae emergence in A. indica treated bags was recorded for S. oryzae stored in Bagco bag at 1.0mg/ml with mean value of 177.67±9.21 and the least value of 107.33±3.76 was recorded for S. oryzae infesting rice grains stored in plastic containers at 1.5mg/ml. There was a significant decrease (p<0.05) in the number of holes bored by S. zeamais and S. oryzae in maize and rice grains treated with Azadirachta indica leaf extract compared to control across various concentrations and storage materials. The highest number of holes bored by S oryzae 390.00±28.22 in infested rice grains was recorded in Calico bag at 0.5mg/ml concentration and the least was recorded in plastic containers at 1.5mg/ml concentration (134.67±11.26). Similar trends were observed with Weevil perforative index and percentage damage. The study concludes that bagco bags treated with A. indica at 1.5mg/ml are more effective for protection of maize and rice grains in storage.