Objective. To study the efficacy of the use of a new strain of Trichoderma viride IMB F-100076 with high antagonistic and cellulolytic activity, in particular its effect on the photosynthetic apparatus and the yield of corn plants. Methods. Study of the effect of T. viride IMB F-100076 on corn94 yield was performed under the conditions of a three-year small-plot field experiment on sodmedium-podzolic soil. The content of chlorophyll a and b in the plants of the experimental variants was determined by spectrophotometry. Methods of mathematical statistics were used in processing the obtained data. Results. Data from a three-year field experiment showed that the application of straw had a negative effect on the yield of corn, which averaged 7.72 t/ha that is 12.3 % less than in the variant without the application of straw (control). Application of the antagonist fungus T. viride IMB F-100076 to the soil simultaneously with straw allowed to obtain an average yield of 9.5 t/ha during three years of study, which is 23 % higher than in the variant with straw. In the control variant (without application of straw and fungal suspension), the yield averaged 8.8 t/ha, which is 14 % higher than in the variant with straw not treated with fungus. It was shown that the content of chlorophylls in corn leaves increases under the influence of T. viride IMB F-100076. For instance, the total content of chlorophyll a and b was 261.04 mg/100 g of leaves, which is 39.0 % higher than in the variant with straw not treatment with a suspension of the fungus, and 15.3 % higher than in the control variant. The obtained results highlight that the treatment of straw with the fungus T. viride IMB F-100076 had a positive effect on the formation of the photosynthetic apparatus of corn plants. Conclusion. Simultaneous application of wheat straw and T. viride IMB F-100076 micromycete, which is characterized by high antagonistic and cellulolytic activity, provides a significant increase in corn yield versus the variant with straw not treated with fungus. The content of chlorophylls a and b in the leaves increases.