Biocontrol Efficacy of <i>Trichoderma virens</i> Against the White Root Rot Causing Pathogen <i>Paramarasmius palmivorus</i> in Field‐Grown Cowpea

This study was conducted to determine the practical feasibility of using Trichoderma virens as a potential biological control agent against Paramarasmius palmivorus . The pathogen was isolated from symptomatic cowpea plants collected in the research field at the Faculty of Agriculture, Rajarata University of Sri Lanka, Anuradhapura, Sri Lanka. The isolated pathogen was initially identified based on morphological characteristics and subsequently confirmed using molecular biological tools (PV216709). In dual culture plate assays, T . virens exhibited an 89.74% inhibition of mycelial growth against P. palmivorus . The efficacy of T . virens formulation was tested in a pot experiment under shade house conditions. Plant growth parameters and disease incidence were monitored. Plant growth parameters were analyzed using a repeated mixed effect model. Colony‐forming units were analyzed using logistic regression in SAS Studio version 9.0 software. The application of T . virens exhibited zero disease incidence under shade house conditions (28°C ± 1°C and 70% RH). Treatment with T . virens significantly enhanced ( p &lt; 0.05) plant height, flower number, pod number, and root length compared to the untreated control. Results revealed that the spores of T . virens were viable and multiplied throughout the experimental period.