Enhancing The Efficacy of Biocontrols and Fungicide Application For Improved Late Blight Management and Yield of Potato

Abstract

Late blight (Phytophthora infestans), whose history dates back to 1840s, still remains a major constrain in potato production. Management of the disease solely depend on extensive use of fungicides that has been implicated, not only on their efficacy, but also has recently raised human health and biodiversity concern globally. Unexpectedly, proposed non-chemical disease management strategies including, use of biocontrols, are yet to yield substantive results that reflect effectiveness and cost saving. Therefore, field trial was conducted to optimize antifungal activities of Trichoderma asperellum and T. harzianum and Ridomil® application in managing potato blight. Seed was pre-treated with T. asperellum and T. harzianum suspensions at concentrations of 3 × 106, 7 × 106 and 1 × 107 CFU/mL and Ridomil® applied at spray intervals of 21, 14 and 7 days. Results revealed that, weather conditions contributed to late blight epidemics development and efficacy of the biocontrols and spray intervals. T. asperellum suppressed late blight more than T. harzianum. Concentration of the biocontrols had significant effect on late blight epidemics, growth and yield. Weekly fungicide application provided higher disease subdual and tuber yield than 14 and 21 days spray intervals. Use of biocontrols at concentration of 7 × 106 and 1 × 107 CFU mL-1 in combination with application of Ridomil® weekly and fortnightly, repressed blight effectively, contributed to higher yield and net farm income than any other combination. The results suggest that, integrated disease management using biocontrols and fungicide could delay late blight epidemics resulting in reduced fungicide application frequencies.