Disease suppression by late season urea sprays on winter wheat and interaction with fungicide

Field studies in the United Kingdom were conducted in 1985 and 1986 to evaluate the effects of late season sprays of urea solution on foliar diseases of winter wheat (Triticum aestivum, L.) and also on the efficacy of propiconazole plus tridemorph fungicide. Urea (supplying 1.3 lb N/ac) applied at flag leaf emergence and again at heading reduced severe Septoria tritici, infection on flag leaves by about 50% in 1985. Urea applications also gave small reductions in levels of mildew in both years, but increased foliar Botrytis cinerea infection in 1985. Propiconazole plus tridemorph fungicide gave good control of all foliar diseases assessed in both years. When urea was mixed with the fungicide in 1985, however, there was a small reduction in control of Septoria and powdery mildew. Fungicide increased grain yield in both years but urea increased yield only in 1985.