Potential of Beauveria bassiana and Metarhizium anisopliae isolates from Benin to control Plutella xylostella L. (Lepidoptera: Plutellidae)

Diamondback moth (DBM), Plutella xylostella L., is the main pest limiting cabbage production in Benin. In the search for biological agents to control the pest, eight isolates of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae indigenous to Benin were screened for virulence against larvae of the insect. The B. bassiana isolates tested were Bba14, Bba5644, Bba5645, Bba5653, Bba5654, and Bba5655, and M. anisopliae isolates were Ma178 and Ma182. The isolate Bba5653 caused 94% mortality of DBM larvae, and the mortality was significantly higher than that caused by any of the other isolates. Cabbage yield was 44.1 t/ha for plots treated with water formulation of Bba5653 at 1 kg conidia powder (CP) per hectare and 41.9 t/ha for plots treated with emulsion formulation of Bba5653 at same CP dose. Each of the yields was approximately threefold higher than the yield in plots treated with the insecticide bifenthrin or in untreated plots. In water formulations, 1 kg/ha of the conidia powder of Bba5653 reduced DBM populations at about the same rate as did 0.75 kg and 0.5 kg CP/ha, but significantly more than did 0.25 kg CP/ha.