Dynamics and management of Alternaria blight disease of Indian mustard (Brassica juncea) in relation to weather parameters

Abstract

Alternaria blight incited by Alternaria brassicae (Schw.) Wiltshire. is a major devastating disease of Indian
mustard [Brassica juncea (L.) Czern & Coss], causing significant reduction in seed yield. The crop grown
in Jharkhand usually suffers seriously from this disease. Considering the economic importance of the disease,
present investigation was under taken to study the effect of weather on disease progression and dynamics of
Alternaria blight. Maximum Alternaria blight severity on leaves and siliqua was observed during 12-18
February, 2013. Mancozeb spray at 40 and 60 days after sowing (das) reduced the disease upto 31 % over
control under field conditions. Maximum temperature positively correlated with disease index. Maximum
temperature of 23.2ºC and maximum and minimum relative humidity (RH) of > 80 %, and 66 % respectively,
with correlation co-efficient of (r) =0.735 for minimum temperature and r=0.515 of minimum RH
respectively, favoured the development of the disease. Forewarning models are expected to guide the farmer’s
timely application of fungicidal sprays.