Suppression of damaging effects of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) by plant powders

Abstract

Powders prepared from plant species available in Nigeria are reported to possess ovicidal, larvicidal, pesticidal, antifeedant and repellent properties against various insect pests and are regarded as environmentally compatible pesticides. This study evaluated the action of Azadirachta indica A. Juss, Hyptis suaveolens Poit. Piper guineense Thonn. & Schum and Cymbopogon citratus Gaern against the damaging effects of Callosobruchus maculatus (F.) in stored cowpea. The experiment was carried out at temperature of 30 ± 1oC and relative humidity of 72 ± 3%. The plant powders were compared at the rate of 2.5 g per 50 g cowpea seeds including the untreated control. The experiment was laid out in a completely randomized design with three replications. The results showed that all the botanicals gave protection to the stored cowpea seeds and significantly (p<0.05) reduced mean adult emergence and seed weight loss (3.75-4.06%) caused by C. maculatus when compared with the untreated control (6.07%). The number of emerged adults from untreated seeds progressively increased with time of exposure compared to the treated seeds. The increasing order of effectiveness of the botanicals in terms of their insecticidal activities against C. maculatus was P. guineense, C. citratus, H. suaveolens, and A. indica. The study, therefore, shows that the botanicals could serve as protectants against C. maculatus in stored cowpea seeds.