Evaluation of potential botanicals against maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae) and angoumois grain moth, Sitotroga cereallela Olivier (Lepidoptera: Gelechiidae) under laboratory conditions

Abstract

ambrosoids at 14.7 LT50 caused 61.1% mortality against S. cereallela which is relatively higher than other treatments from the first day to 20 days exposures. Low mortality was recorded from A. sativum at 18.01 LT50 with 50%, C.citratus at 18.3 LT50, M. lanceolata at 16.2 LT50 and E. kebericho at 14.5 LT50 caused 55% against S. zeamais. In addition, M. lanceolata at 219.8 LT50 and E. kebericho at 338.1 LT50 with 27.8%, A. indica bark at 30.38 LT50 and C.citratus at 171 LT50 records 39% mortality against S. cereallela. Compared to the untreated control as well as increase in the concentration of cooking oils namely, G. hirsutmn scored 100% and B.carinata scored 90% against S.zeamais and 77.8% against S.cereallela over 20 days of exposures. The decrease in progeny emergency and grain damage in terms of grain holes number and weight loss was significantly seen by the grains treated with the two cooking oils. The two cooking oils were seen to be the best and further experiment was done by taking four application rates (0.2ml, 0.3ml, 0.4ml and 0.5ml) out of which maximum mortality and minimum adult progeny was emerged from gains treated with higher concentrations (0.4 and 0.5 ml) agains both test insects. Similar trend was registered from the rest variables. It is recommended that the two cooking oils were found to be the most potent bioinsecticides against maize weevil and grain moth on par with standard check chemical, Malathion.