Efficacy of the entomopathogenic fungus Metarhizium anisopliae (Clavicipitaceae: Hypocreales) against the black bean aphid (Aphis fabae Scopoli, 1763) under laboratory conditions

Black bean aphid (BBA) is a serious insect pest that severely significantly impacts French bean production. Over-reliance on synthetic chemicals to reduce economic losses caused by aphids poses serious environmental and human health threats. Biopesticides containing entomopathogenic fungi (EPF) have potential as viable alternatives that can be incorporated into integrated to manage such insect pests. The efficacy of Metarhizium anisopliae against BBA was assessed in the laboratory under a complete randomized design (CRD) design with five replicates. Data was analysed using SAS 9.4 (2021). In part one, Metarhizium anisopliae products caused bean aphid mortality etween 60.1% and 95.5%. Mazao supreme (4×108 spores/ml) and Metarril (4×108 spores/ml) caused the highest mortality (95.5%) and the lowest concentration of irrespective product caused the lowest mortality (60.1%) after treatment application. In part two, alpha-cypermethrin caused the highest aphid mortality (99.3%), followed by Metarril (84.2%), Mazao (80.7%) and biomagic had the lowest (68.4%) mortality after treatment application. Alpha-cypermethrin had the lowest lethatl time (LT50), causing 50% aphid mortality, followed by Metarril, Mazao supreme, and biomagic. Differents treatments had varying effects on nymph numbers. Alpha-cypermethrin caused 50% aphid mortality, followed by Metarril, Mazao supreme, and biomagic, with varying effects on nymph numbers. The study recommends incorporating Metarhizium anisopliae-based biopesticides, particularly Metarril by small holder farmers to offer a cost-effective integrated pest management approach for managing BBA (adults and nymphs) in French bean production while reducing reliance on synthetic chemicals. Keywords: Black bean aphid, biopesticides, French beans