Seasonal Occurrence and Severity of Early Blight of Potato Caused by Alternaria solani (L.) in Relation to Weather Conditions

Abstract

The potato ranks third in global significance as a human food crop, trailing only rice and wheat. However, the potato plant is susceptible to fungal diseases, including Early blight, Alternaria solani, which can lead to significant yield losses in potato crops. The present investigation was conducted for the management of early blight of potato by using bioagents and newer fungicides. The experiment was conducted at experimental fields near Shri Venkateshwara University, Amroha, UP. A survey was conducted, and the daily weather data were collected from the weather station at Shri Venkateshwara University. The crop was regularly observed for the first appearance of the disease. Disease severity was recorded using a score chart consisting of a 0-9 scale. Fifty leaves were randomly selected from the field for measurement of disease severity. The results revealed that the early blight of potato disease occurred every year at Shri Venkateshwara University, Rajabpur, Amroha, UP. The first appearance of early blight was observed on 12th December 2023 with the value of 0.17 per cent at the maximum temperature 23.69, minimum temperature 2.15, and mean temperature 12.92, relative humidity 92.26%, minimum relative humidity 37.26%, mean 64.76 and 0.00 sun shine hours and maximum severity of 31.28 per cent was noted on 12. January 2024, after 32 days of the first appearance of disease at the maximum temperature 23.470C and minimum temperature 5.54, Mean 14.51 0C, relative humidity maximum 95.38 % and minimum 65.37 %, mean 80.38% and sunshine hours 6.12, evaporation 1.25 and rainfall 0.00. It was clear that the infection rate increased suddenly from 17.12.23 to 25.12.2023 and from 28.12.2023 to 11.1.2024, which might be due to the occurrence of rainfall, resulting in high relative humidity and low sunshine hours, which are optimum for the pathogens' growth. The results also showed that during second year 2024-25, the first appearance of early blight of potato A. solani was observed on 17th December, 2024 with the value of 0.95 per cent at the 24.670C maximum temperature and 7.58 minimum temperature, mean 16.13 per cent maximum relative humidity was 90.38 per cent, 52.57 per cent minimum and mean 71.48 relative humidity and 5.26 sun shine hours and 2.25 evaporation and the maximum disease severity of 28.54 per cent on 15 January, 2025 after 33 days first appearance of disease at maximum and minimum temperature 21.540C - 4.280C and mean 12.91 0C, maximum, minimum and mean relative humidity 94.57% – 69.54% and 82.06 % sun shine hours 5.98 and evaporation 1.39 respectively. It is clear that during 2024-25, cloud covered continuously at frequent intervals of date, but light rainfall occurred on 12th and 15th January, considering favourable conditions for the development of the disease, resulting in increased infection of the potato crop A. solani.