Control of coffee rust (Hemileia vastatrix) with Trichoderma spp.: quantitative assessment using the Pliman package

Background/Objective. Coffee rust (Hemileia vastatrix) reduces coffee production and profitability. Alternatives for its control (chemical and genetic) have not been fully effective; therefore, the use of microorganisms such as Trichoderma has been proposed. Currently, tools like the Pliman package provide a quantitative alternative for assessing disease severity. The objective was to evaluate the effectiveness of Trichoderma strains applied to the soil in reducing the severity of H. vastatrix through digital image analysis using the Pliman package. Materials and Methods. The effect of Trichoderma harzianum (Th), T. asperellum (Ta), and their consortium (Th_Ta) was evaluated at two concentrations (1×10⁸ and 1×10¹² conidia mL⁻¹) on 42 ‘Catuaí Amarillo’ coffee plants, both asymptomatic and symptomatic. Soil applications were performed every two months for one year. Disease severity was quantified using the Pliman package in RStudio. The data were analyzed with a factorial ANOVA and Tukey’s tests (p<0.05). Results. Trichoderma treatments significantly (p < 0.05) reduced disease severity compared with the control. Treated asymptomatic plants showed the lowest severity (Th_Ta=5.99%, Th=5.61%, Ta=8.61%). In symptomatic plants, T. asperellum (Ta) was the most effective, reducing severity to 8.25%, a value not significantly different from that of treated asymptomatic plants. No significant differences were found between the concentrations used (1×10⁸ and 1×10¹² conidia mL⁻¹). Severity showed a clear seasonal variation, being lower during dry months (February=4.89%, August=4.71%, and April=5.23%) and higher during rainy months (June=15.29%, October=10.79%, and December=23.39%). Conclusion. Soil application of Trichoderma spp. significantly reduces the severity of coffee rust. The most effective treatments were the consortium of T. harzianum and T. asperellum in asymptomatic plants, and T. asperellum alone in symptomatic plants, with the concentration of 1×10⁸ conidia mL⁻¹ being the most advisable due to its efficacy and economic feasibility. Finally, the Pliman package proved to be an effective tool for the objective quantification of the disease.