Preparation and fungicidal bioactivity of wettable powder formulations of Trichoderma asperellum

We prepared microbiological fungicide using conidial germination powder and freeze-dried fermentation broth powder of Trichoderma asperellum in this study. Based on measuring the bioactivity of primary adjuncts to T. asperellum, the effects of adjuncts on formulation properties were further tested according to orthogonal experimental design, and then the optimal species and contents of the adjuncts were finally determined. The wettable powder was formulated with a Muller mixer to blend conidial germination and freeze-dried fermentation broth powder of T. asperellum and adjuncts. The inhibitory activities of wettable powder formulation to Sclerotinia sclerotiorum with different ratios of conidial germination to freeze-dried fermentation broth powder of T. asperellum were evaluated. The results showed that the optimal mass ratio of conidial germination to freeze-dried fermentation broth power of T. asperellum in the wettable powder formulation was 1∶1, and the wetting dispersant was composed of 1% Morwet EFW, 5% TERWET 1010, 5% Morwet D425 and 7% calcium lignosulfonate, using 0.3% nano zinc oxide as UV protectants and diatomite as carrier to make up 100%. The conidial germination was 88.57%, mass suspension percentage was 81.79%, conidial suspension percentage was 80.12% and average particle size was 27 μm, and the wetting time for the formulation was10 s, which accorded with the standard for commercial formulations,i.e., small particle size, high suspensibility and good shelf life. All different mixed formulations had different synergistic effects, but 1∶1 ratio of formulation was significantly synergistic. The wettable power formulations (1 600×) containing both conidial germination and freeze-dried fermentation broth power had 21.67% and 12.09% higher control efficacy to S. sclerotiorum than that of wettable powder formulations containing only conidial or freeze-dried fermentation broth power. The inhibition of wettable power formulation to S. sclerotiorum ranged from 64.17% to 88.67%. Therefore, this formulation is an environment-friendly green pesticide,and our study provides a new bio-fungicide in biological control of plant diseases in agriculture and forestry.