Optimization of fermentation conditions for Trichoderma hamatum T2 and its efficacy against larch shoot blight caused by Neofusicoccum laricinum.

Trichoderma hamatum T2 is an antagonistic fungus with biocontrol potential. In this study, single-factor experiments combined with response surface methodology were employed to optimize liquid fermentation conditions for T2, in order to enhance its inhibitory efficacy against Neofusicoccum laricinum, the causal pathogen of larch shoot blight. Using Rose Bengal medium as the basal medium, key fermentation factors, including carbon source, nitrogen source, inorganic salts, and culture conditions, were optimized. Under the optimized fermentation conditions, the sterile fermentation filtrate of T. hamatum T2 exhibited an inhibition rate of 78.8% against N. laricinum, compared with 28.0% obtained using the unoptimized PDA medium. In pot experiments, T2 treatment reduced disease incidence from 76.67% to 16.67%, with a control efficacy of 78.26%. In field trials, the control efficacies were 53.33% in 2024 and 60.26% in 2025. Following pathogen inoculation, T2 treatment significantly increased POD and SOD activities in larch needles, and promoted the accumulation of flavonoids and total phenols. T2 treatment also elevated GR activity, as well as the contents of non-structural carbohydrates, soluble sugars, starch, and proline. Response surface methodology effectively optimized the fermentation conditions of T2. This fungus enhances host resistance by inducing the plant antioxidant system and secondary metabolism, exhibiting promising potential for the biological control of larch shoot blight.