Prevalence, Epidemiology and Forecasting of Alternaria Blight of Indian Mustard (Brassica juncea) in India

PD Meena, Amrender Kumar, Vinod Kumar, Mamta Sikarwar, Pankaj Sharma, C Chattopadhyay and PK Rai


First appearance of Alternaria blight (AB) disease of Indian mustard (Brassica juncea) on leaves occurred between 65
and 98 days after sowing (d. a. s.), 83, 87, 98, 65, d. a. s. having higher frequencies in 2010–11 to 2013-14 respectively,
being highest in respective years at 45, 46, 75, 45, 76 d. a. s. The disease first appeared on pods between 67 and 142 d. a.
s., being highest at 99 d. a. s. Severity of AB disease on leaves was positively correlated to a maximum daily temperature
of 18–27 °C, minimum daily temperature of 8–12 °C, daily mean temperature >10 °C, >92 % morning relative humidity (r.
h.), >40 % afternoon r. h. and mean r. h. of >70 % in the preceding week. Location and cultivar-specific models might
forecast the crop age at which AB first appeared on leaves, the highest leaves blight severity, and the crop age when
blight severity was highest on leaves at least one week ahead of first appearance of the disease on the crop. Keeping in
view the normal date of sowing (22 October), the models have been tested in the farmers’ field for Bharatpur. Although,
data revealed that AB severity decreased by 10% over six locations during 2001 to 2015 on B. juncea cultivar Rohini with
delayed appearance of AB. There may be defensive difference among age of plant, cultivars and species of Brassica for
showing disease response. The AB severity trend on leaves at all six zones was fluctuating between 30 to 50%. AB
disease severity trends in zone II [Hisar (HSR), Ludhiana (LDH), Bhatinda (BTH), Sriganganagar (SGN)] showed static
trend with R² = 0.036 (y = -0.221x + 39.08) and similar trend was also observed in zone III [Bharatpur (BHP), Kanpur (KPR),
Faizabad (FZB), Morena (MOR)] with R² = 0.011 (y = -0.201x + 41.10). Particularly in zone V at Jagdalpur (JAG) and
Berhampore (BER), AB severity drastically decreased by R² = 0.661 (y = -2.089x + 46.40). However, AB severity trend on
cultivar Rohini and Varuna at Bharatpur was observed below 15% with R² = 0.282 (y = -1.106x + 23.50) since 10 years
which was >25% during 2003 to 2006. Only models with reasonable prediction accuracy when tested with an independent
data set will allow farmers to aware about status of disease and to make timely and effective fungicidal sprays.


Alternaria brassicae, Brassica juncea, epidemiology, forecasting models, weather based regression model and prevalence

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