Effectiveness of Different Plant Extract for the Control of Black Bean Aphids and Abundance of Beneficial Insects on Common Beans

Experiment was conducted at Ndugutu village, Morogoro from December, 2020 to August, 2021 to investigate effects of three selected pesticidal plant extracts on the abundance of Black Bean Aphids (BBAs) and beneficial insects on common bean crop.  A Randomized Complete Block Design with three replications was used with pesticidal plant species extracts of Dysphania ambrosioides, Vernonia amygdalina and Derris trifoliata leaves with three different concentrations (i.e. 140, 200 and 240) g/L as treatments.  Results show that there was a significant difference (p= 0.0001) amongst different treatments. Among other pesticidal plants, V. amygdalina with concentration of 140, 200 and 240) g/L and D. trifoliata 240 g/L were the most effective on the reduction of abundance of aphids and incidence during dry season. The beans yield difference was significant (p = 0.010) across treatment during the two seasons.  The second, highest bean yield was recorded in bean plots treated with D. trifoliata and D. ambrosioides with a concentration of 240 g/L each contributing to a mean average of (993.5 and 1165.7) kg/ha whereas lowest being D. trifoliata at 200 g/L with a mean average of (494.7) kg/ha. This study has demonstrated that pesticidal plant extracts have ability to control insect pest population. Therefore, the studied pesticidal plants should be considered in Integrated Pest Management due to their good management efficacy and safety issues for the consumers’ and environment.