Temporal and Spatial Variability of Potato Early Blight and its Association with Weather Variables SATENDRA KUMAR SHARMA 1 , A.K. SRIVASTAVA 2 * AND D.S. TOMAR 3 1,3 Departmentof Plant Pathology, College of Agriculture Tikamgarh, JNKVV, Madhya Pradesh 2 Department of Agro-meteorology, College of Agriculture Tikamgarh, JNKVV, Madhya Pradesh ABSTRACT Field experiment, as well as roving survey of farmers’ field, was conducted in blocks of Tikamgarh district of Bundelkhand agro-climatic zone VII of Madhya Pradesh to record the temporal and spatial variability of potato early blight during rabi 2018-19. Weekly data on early blight of potato from the field experiment and fortnightly data from the farmer’s field were collected. The spatial and temporal variability on the incidence and intensity of the diseasewere noted. The lowest incidence and intensity were recorded at Prithvipur and Palera block, respectively and the highest disease incidence and intensity at Baldeogarh block. The rainfall and temperature were correlated with disease intensity. The rainfall and temperature are closely associated with the disease severity. Mean and minimum temperatures above 15 and 6°C accompanied with rainy days are congenial weather conditions for increase in intensity of the disease. Key words: Early blight, Potato, Incidence, Intensity, Weather for its production. India is the second largest producer of potato after China, with an area of 2.16 million ha, with production of 46.55 million ton and productivity 21.5 t/ha in 2016-17 (Anonymous, 2017 a). In India, Uttar Pradesh is the major potato producing state with the production of 15.56 million tons and share 31.54 per cent, followed by West Bengal, Bihar, Gujarat and Madhya Pradesh (Anonymous, 2018). Potato is one of the important tuber crops cultivated in Tikamgarh district in rabi season. The annual production was 0.037 million tons from 0.003 million hectares area with an average productivity 14.5 t/ha (Anonymous, 2017 b). Early blight of potato is caused by two pathogens viz. Alternaria solani (Jones & Grout) and A. alternata (Fr.) Keissler, but in some areas only Alternaria solani is considered as the causative organism of this disease. The spores of *Corresponding author, Email: ajay-weather@yahoo.com Vol. 19, No. 1, pp. 67-75 (2019) Journal of Agricultural Physics ISSN 0973-032X http://www.agrophysics.in Introduction Potato (Solanum tuberosum L.) is known as a king of vegetable crop of Madhya Pradesh as well as India. It is consumed as a popular source of carbohydrate, and can be used both for table consumption as well as in many processed products. More than 75 per cent of the dry matter of the potato is starch but it also contains protein, fibers and small amount of fatty acids (Prokop and Albert, 2008). It is also rich in minerals such as potassium, phosphorus, magnesium and vitamins like B1, B3 and B6 (Camire et al., 2009). Potato is grown in more than 100 countries, under temperate, sub-tropical and tropical climatic conditions. It is essentially a cool season crop and temperature being the main limiting factor Research Article