Rust Outbreak vs. Heat Stress: Resolving the Weather-Disease Nexus in Wheat

The present study was planned to evaluate the association between meteorological parameters and yellow rust severity in wheat during three contrasting seasons: 2012-13 (rust epidemic year), 2021-22 (heat stress year), and 2022-23 (recent rust year). Rust severity was recorded as 100, 56.75 and 58.42% in 2012-13, 2021-22, and 2022-23, respectively. Correlation analysis revealed that maximum temperature (Tmax) was positively associated with rust severity. Minimum temperature also showed a strong positive correlation Morning relative humidity (RHm) and evening relative humidity (RHe) exhibited negative correlations, with RHm r = -0.65 to -0.72 and RHe r = -0.73 to -0.79, strongest in 2021-22. Rainfall had a weak positive correlation in 2012-13 and 2022-23, but a significant negative one in 2021-22 (r = -0.64). Sunshine hours were positively correlated with rust severity (r = 0.88 in 2021-22). During the disease phases, maximum and minimum temperatures were lowest in 2012–13 and highest in 2021-22. Relative humidity and rainfall were highest in 2012-13, followed by 2022-23, and minimum in 2021-22. Sunshine hours were least in 2012-13 and highest in 2022-23. Thus, 2012-13 was characterized by cooler temperatures, higher humidity, and greater rainfall conditions highly favourable for rust development. In contrast, 2021-22 experienced higher temperatures, lower humidity, and reduced rainfall, contributing to heat stress conditions. The year 2022-23 exhibited intermediate weather conditions, favouring moderate rust development. These findings highlight the importance of integrated weather-based forecasting for effective yellow rust management in wheat.