Influence of Prevailing Weather Variables on Karnal Bunt Dynamics in Wheat

Field experiments were conducted with three wheat varieties viz. PBW 725, HD 2967 and HD 3086 sown on three different dates (14-15^th October, 8-9^th November and 3^rd-4^th December) with two microclimate modification levels with four replications at the Research Farm, Department of Climate Change and Agricultural Meteorology, Punjab Agricultural University, Ludhiana (Ldh), India and Regional Research Station, Gurdaspur (Gsp) during rabi season of 2021-22 and 2022-23. The main objective of study was to investigate the effect of prevailing weather conditions and microclimatic modification on Karnal bunt incidence of wheat under two agroclimatic zones of Punjab. Karnal bunt incidence was highest in PBW 725 (17.1–12.4% at Ludhiana, 20.3–15.4% at Gurdaspur), followed by HD 2967 (16.1–11.4% at Ludhiana, 19.3–13.9% at Gurdaspur) and HD 3086 (15.5–10.6% at Ludhiana, 17.9–12.9% at Gurdaspur). November sowing (D₂) and additional water sprays (M₂) significantly increased Karnal bunt incidence. The highest incidence was observed in D₂M₂ (17.6–12.4% at Ludhiana, 20.4–15.4% at Gurdaspur), while the lowest was in D₃M₁ (15.1–10.5% at Ludhiana, 18.1–12.9% at Gurdaspur). Higher Karnal bunt incidence during 2021-22 than 2022-23 can be primarily attributed to lower maximum and minimum temperature and higher morning and evening relative humidity during 2021-22 than 2022-23. In 2021-22, the maximum amount of rainfall was received between the 1^st and 5^th SMW [149.3 mm (Ldh) and 235 mm (Gsp)] which had positive influence on disease incidence, while in 2022-23, it was concentrated between the 11^th and 14^th SMW [77.2 mm (Ldh) and 78 mm (Gsp)] at both locations. The booting stage of wheat sown in November coinciding with low temperature, high humidity and rainy days are crucial parameters for Karnal bunt development.