Bioactivities of Six Indigenous Ghanaian Plants in Managing Sitophilus Zeamais and Prostephanus Truncatus in Stored Maize in Volta Region

Abstract

The increasing rate of pest resistance, high cost and health risk in the use of insecticides have become an issue of Public concern. This research therefore was undertaken to identify and assess botanicals that are used by the farmers of Volta Region to manage S. zeamais and P. truncatus in stored maize grains. A survey conducted revealed A. indica, C. anisata, P. amarus, P. nitida, V. amygdalima , N. latifolia and M. charantia as grain protectants against stored insect pests. All the above mentioned botanicals were used for the experiment except A. indica since its potential against grain storage pest has long been established. Dried powders at (5 and 10%) and aqueous extracts (0.1 and 0.2 g/mL) of botanicals were prepared and evaluated for their insecticidal activity against P. truncatus and S. zeamais. The potency of botanicals varied with plant species and dose rate. Maximum toxicity of plant powders and methanol extracts to insects were observed in V. amygdalima treatment. At higher concentration of 0.2 g/mL, toxicity of V. amygdalina was 83.3 and 86.7% to P truncatus and S. zeamais respectively. All plant extracts at 0.2 g/mL showed significant (P<0.05) difference in repellency to Actellic; however, C. anisata expressed the highest repellent activity to P. truncatus and S. zeamais at 80.0 and 66.7% respectively. There was reduction in oviposition and emergence of eggs when grains were treated with extracts of botanicals compared to the control. There was reduction in the number of adult insects when immature stages of insects were treated with methanol extracts of botanicals. These results suggest that the botanicals tested have the potential in the development of post-harvest protection technology against, P. truncatus and S. zeamais as the major pest of stored grains. It is therefore recommended to be used by farmers to control P. truncatus and S. zeamais in stored maize grains.