Evaluating Pre-planting Trichoderma asperellum Application for Biocontrol of Macrophomina phaseolina in Screenhouse-Grown Cowpea

Abstract

Cowpea is recognised for its importance as a food and forage crop for animals. However, Macrophomina phaseolina, a fungus that causes pre-harvest crop loss, affects its production. In this study, Trichoderma was employed as an alternative to synthetic fungicides that negatively impact biodiversity to manage rot disease in cowpea. Three strains of Trichoderma asperellum were isolated from the soil. The spore suspensions of the Trichoderma strains were formulated into seven treatment combinations and applied to the cowpea soil before planting to investigate their biocontrol potential on M. phaseolina and their effects on cowpea biomass. The result showed that Trt3 (54.5417 cm), Trt1 (54.0625 cm) and Trt4 (52.8250 cm) had higher plant height than the negative control (M. phaseolina only (44.9667 cm)). Also, Trt7 (0.5446 cm) and Trt5 (0.5313 cm) had a higher stem girth performance than in the negative control (M. phaseolina only (0.3333 cm)), while Trt7 (24.958), Trt3 (21.417) and Trt6 (20.083) recorded a higher leaf number than in the negative control (M. phaseolina only (8.833)). Zero disease incidence was observed in Trt3 (0%) and Trt7 (0%) upon treatment with the Trichoderma formulations. Zero disease severity was recorded in Trt3 and Trt7 (0%), compared to the negative controls, which displayed 100% disease incidence and severity. The pre-planting Trichoderma application enhanced cowpea biomass and reduced disease incidence and severity compared to the negative control. Therefore, Trichoderma is an effective bioagent for controlling diseases caused by M. phaseolina in cowpea and stimulating its overall performance.