Influence of agro-ecological zone on azadirachtin concentration and efficacy of neem leaf powder against sitophilus zeamais in Uganda

Abstract

Using synthetic insecticides to control Sitophilus zeamais has raised serious concern on the environment and human health. There is need to adopt a more affordable and eco-friendly option such as neem bio pesticide. Neem is reported to contain AZA active ingredient with insecticidal properties against S.zeamais. Neem leaf powders obtained from four AEZs were evaluated for AZA cone. and efficacy against S.zeamais. Extraction of AZA in neem leaf powders was done in two replicates using 100g of fine powder each obtained from the four AEZ while quantification was done using HPLC. Efficacy of neem leaf powder against S.zeamais was assessed using four doses: 0.5, 1.0, 1.5 and 2.0g. There were significant differences in cone. of AZA in neem leaf powders from the 4 different AEZs. Lake Victoria Crescent which experiences moderate climate with average rainfall had the highest AZA content (35.23 mg/g) while Karamoja dry land with hot climate had the lowest AZA (27.76 mg/g). Further, maize grain treated with neem leaf powders obtained from Lake Victoria Crescent with the highest cone. of AZA had the lowest mean weevil count (13/100g) with lowest mean number of damaged grains (4.8 /100g) while Karamoja dry land with the lowest AZA cone had the highest mean weevil number (25 /100gm) and the highest mean number of damaged maize grains (11. 7/100g). Neem leaf powder dosage of 2.0g effectively reduced the mean grain damage to I 0.0 compared to 20.0 when treated with 0.5g. When using neem leaf powder as an option, customized quantities should be used basing on the AEZ from which the neem leaf product is obtained and those using neem products from Karamoja dry land, should use more quantities compared to Lake Victoria Crescent AEZ.