Full explanation
Wheat and barley have a short heading window (5–7 days optimum, 7–10 under stress). It's the decisive yield-forming stage: grain number per ear is determined here (80%), along with potential ear length and spikelet count. T2 fungicide (flag leaf BBCH 37–39, or heading start BBCH 51–55) is mandatory in intensive production: triazole + strobilurin or triazole + SDHI (Priaxor, Revytrex, Tangocell, Ascra Xpro) protects the top 3 leaves + ear from Septoria, rust, helminthosporium. Skipping T2 costs 10–25% yield in an epiphytotic year. Combine with foliar nutrition: Mg + Cu + Mn + urea 8–12 kg/ha in tank mix. Delayed heading (from late sowing, cold spring) risks entering July drought during grain fill → low TSW.