Forewarning models for Sclerotinia rot (Sclerotinia sclerotiorum) in Indian mustard (Brassica juncea L.)

Sclerotinia sclerotiorum (Lib.) de Bary has worldwide distribution and causes diseases in more than 500 host plants. Sclerotinia rot is a menace to cultivation of oilseed Brassica crops worldwide. The epidemiology of Sclerotinia rot (SR) of Indian mustard (Brassica juncea L.) was investigated during 2004-2012 crop seasons, and based on 8 year of disease data. The forecasting models were developed first time in Indian conditions and then validated in 2012-13. The carpogenic infection initiated in 52 standard week (last week of December) and continued during 1 to 3 standard weeks (first three weeks of January). Disease first appeared after closure of the crop canopy when flowering started. During epidemics, the 8 year mean daily maximum and minimum air temperature was 19.4 and 5.1A degrees C, morning and afternoon RH 95 and 62 per cent, bright sunshine hours 4.9 and rainfall was 1.4 mm, all are conditions favourable for disease development. The R (2) value of the regression analysis between observed and estimated SR prevalence was 0.98. Disease forecasting could provide the growers with information for well timed application of fungicides to control SR and this would be beneficial economically.