SURVEY OF INSECTICIDAL PLANTS IN PARTS OF NIGERIA AND EFFECTS OF THEIR POWDERS ON MAIZE WEEVIL ATTACK.

Abstract

A survey of the plants used traditionally for maize storage was conducted in the villages of some selected Local Government Areas of Osun State in 2009. Bioefficacy of powders of six identified plants were also evaluated against maize weevil Sitophilus zeamais Motschulsky at the rates of 0g, 0.5g, 1.0g and 2.0g per 25g of maize grains. The results of the survey revealed six bioactive plants being used by the peasant farmers for the protection of their maize in storage against maize weevil, Sitophilus zeamais. These plants were Aframomum melegueta (Rosch) k. Schum, Azadirachta indica A. Juss, Capsicum annum L., Ficus exasperata Vahl., Nicotiana tabacum L. and Tetrapleura tetraptera (Schum and Thonn) Taub. Powders from seeds, fruits and leaves of these plants were used for the evaluation against maize weevils. Results showed that at 2.0g/25g of maize grain, powder of each of the six plants increased mortality and reduced adult emergence of the weevils. The powders of F. exasperata and C. annum had the highest percentage mortality (90.00 and 80.00) respectively when compared with other treatments. The powders significantly (p<0.05) reduced adult emergence. Significant reduction in weight loss in maize grains treated with each plant powder was obtained at 2.0g/25g maize grains when compared with other levels of concentration. The results obtained also showed that the effects of these plant powders were not significantly different from one another when compared their effects on percentage mortality, adult emergence of maize weevil and maize grain weight loss at 2.0g level of concentration. The powders of these plants exhibited promising potential in protecting maize grains against weevil attack as observed in this study confirming the traditional use of the plants for protection of storage maize by farmers in the selected Local Government Areas of Osun State.