Epidemiological Study of Alternaria Leaf Spot of Cauliflower in Jorhat District of Assam, India

Abstract

Alternaria leaf spot is a major disease of cauliflower that can reduce yield and quality under favourable environmental conditions. A field experiment was conducted during the 2023–2024 rabi season at the Horticultural Orchard, Assam Agricultural University, Jorhat, Assam, to evaluate the effects of transplanting date and weather parameters on disease development. The experiment followed a randomised block design with four transplanting dates—15 October, 15 November, 15 December and 15 January—and five replications. Disease severity was recorded at 15-day intervals and expressed as per cent disease intensity (PDI). The crop transplanted on 15 October recorded the lowest final PDI (15.60 at 90 DAT) and the lowest area under the disease progress curve (AUDPC; 333), whereas the crop transplanted on 15 January recorded the highest final PDI (28.40) and AUDPC (1416). Maximum temperature, minimum temperature and bright sunshine hours generally showed negative associations with PDI, whereas morning relative humidity showed a positive association. The combined effects of the weather variables explained 74.17–96.32% of the variation in disease intensity. Early transplanting also produced superior growth and yield attributes. Under the conditions studied, transplanting in October was associated with lower disease pressure and higher cauliflower yield, although validation across seasons and locations is required before wider application.