Influence of site factors on yield response of winter wheat to fungicide programmes in England and Wales, 1979–1987

Results of 460 field experiments between 1979 and 1987 incorporating one, two and three fungicide sprays, with a range of active ingredients, were analysed according to site factors including previous crop, sowing date and geographical area. The average untreated yield was 7–48 t/ha, although this fluctuated widely from 6 15 t/ha in 1985 to 9 411 ha in 1984. A single spray at flag‐leaf emergence gave an average yield increment of 0 59 t/ha over plots receiving no fungicide. The addition of a second spray at the first‐node growth stage gave an extra benefit of 0.22 t/ha, while an additional third spray at ear emergence gave a further 0.28t/ha. The effects on yield of different spray timings were modified by other factors, of which sowing date and previous crop were most important to the first‐node spray, and cultivar and geographical area to the ear emergence spray. The data suggest that all crops would benefit economically from a broad‐spectrum fungicide applied at flag‐leaf emergence. Additionally, crops sown in September, those following winter wheat and those in regions bordering the North Sea respond well at the first‐node stage to a fungicide active against eyespot.