Management of Early and Late Blight Diseases on Potato Crop Through Sequential and Alternate Application of Mancozeb and Pseudomonas fluorescens

ABSTRACT Early blight ( Alternaria solani ) and late blight ( Phytophthora infestans ) severely threaten potato production, causing high yield losses. A field study was conducted to evaluate the sequential and alternate applications of Mancozeb 75% WP 1500 g/ha and Pseudomonas fluorescens 1.75% WP 2500 g/ha and vice versa at 10 days interval for managing blight diseases of potato. The terminal observation recorded at 10 days after third spray showed that alternate application of Mancozeb 75% WP (first spray) + P. fluorescens 1.75% WP (second spray) + Mancozeb 75% WP (third spray) was the most effective schedule with low late blight Per cent Disease Index (PDInd) 8.27% and 9.14% and Per cent Disease Incidence (PDInc) 8.91% and 11.67% during 2024–2025 and 2025–2026, respectively. Similarly, the treatment effectively controlled early blight with respective PDInd 10.12% and 11.48% and PDInc 17.87% and 14.70% and resulted in higher tuber yield 21.70 and 23.18 t/ha. This was closely followed by the sequential application of Mancozeb 75% WP (first spray) + Mancozeb 75% WP (second spray). The treatment P. fluorescens 1.75% WP (first spray) + Mancozeb 75% WP (second spray) + P. fluorescens 1.75% WP (third spray) was the next best treatment. No phytotoxicity to the crop and no adverse effects on natural enemies were observed. The use of Mancozeb 75% WP 1500 g/ha (first spray) + P. fluorescens 1.75% WP 2500 g/ha (second spray) + Mancozeb 75% WP 1500 g/ha (third spray) at 10 days interval from the initiation of blight diseases on potato crop is supported.