Occurrence and Management of Late Blight Diseases of Tomato in Terai Zone of West Bengal

Background: The objective of this study was to determine the influence of weather indices on disease incidence and search efficient and economically profitable management option as compared to others in field conditions against tomato late blight disease.

Methods: The seedlings were planted in a randomised block design. Seedlings were planted on four different dates with seven treatments and three replications to study the disease incidence and efficacy of new generation fungicides. The variety “Patharkuchi” was used for the present study. The experiment was conducted at Agricultural Farm, UBKV, West Bengal. Different weather parameters were collected from the nearest automatic weather station.

The experiment involved seven different treatments permutation for management of late blight disease. The fungicidal sprays were done as soon as the late blight disease was observed in the tomato field. The disease incidence was recorded in percentages of diseased plants out of total plants studied. The disease severity was assessed by PDI value in 0 to 9 scale.

Results: It was observed in the study, that the number of days from sowing to initiate late blight symptom on tomato was an inverse function (Y=a+bx-1) of average maximum humidity and temperature and R2 values of the equation were statistically significant at 1% level of significance. Two sprayings with Ametoctradin + Dimethomorph @ 0.3%WP showed lowest disease severity of 6.14% and 83.11% reduction in disease severity over control at 90 days after planting (90DAP) which was significantly at par with the Cholorothelonil 40% w/w + Difenconazole 4% w/w SC fungicide. The data showed that fruit yield was significantly higher in Cymoxanil + mancozeb @ 0.3% treatment combinations (118.93 q/ha) compared to control (62.40q/ha).

Conclusion: Date of initiation of the disease positively correlated with the maximum relative humidity and negatively correlated with maximum temperature and sunshine hours. Two sprayings with Ametoctradin + Dimethomorph @ 0.3% and Cholorothelonil 40% w/w + Difenconazole 4% w/w SC fungicides could effectively manage tomato late blight disease.