Correlation analysis of weather variables influencing white rust diseases in Indian Mustard

Abstract

White rust is a major devastating disease in Indian mustard causing significant reduction in yield as well as quality. Present investigation was under taken to study the impact of weather variables on disease severity and progression of white rust in different dates of sowing. The maximum disease intensity was recorded as 58.3% (8th SMW) and lowest (0.4%) during 2nd SMW in 1st week of Nov. sowing (D5) during Rabi, 2023-24. It was inferred that across all seasons, Tmax and Tmin showed a consistently negative correlation with white rust severity, indicating that lower temperatures favoured higher disease incidence. Notably, Tmin exhibited stronger negative correlations as compared to Tmax and significantly promoted disease progression. In contrast, RHm displayed positive correlation with PDI across all sowing dates and seasons. Evening humidity (RHe) also exhibited a positive but relatively weaker correlation. Rainfall showed weak and variable correlation patterns across seasons. Among the sowing dates, late sowings consistently showed stronger correlations with conducive weather parameters (lower Tmin and higher RHm), indicating that delayed sowing increases the likelihood of white rust development due to favourable microclimatic conditions. Overall, the pooled correlation analysis confirmed that cooler temperatures and high morning humidity are key drivers of white rust epidemics in mustard under S.W. Haryana agroclimatic conditions.