Surveys of Diseases of Winter Wheat in England and Wales, 1970-75.

Samples from 265-333 randomly selected crops of winter wheat in England and Wales were taken annually from 1970 to 1975 after heading, the main sample being at the milky-ripe growth stage. The percentage of the area of the lop two leaves affected by diseases was recorded and, in the last five years, samples were tested for infection by barley yellow dwarf virus: in 1975 stem base diseases were recorded. Septoria was the most common and severe disease in four of the six years. In 1970 mildew was most severe and, in 1975, brown rust. The severity of infection by Septoria tended to be greater in southern and western areas in wetter summers and in crops following a previous cereal. Yellow rust was most severe in 1972, when it was very prevalent on cv. Joss Cambier. In 1973 the disease was less severe, but in 1974 and 1975 the severities of both yellow and brown rusts increased in association with the popularity of susceptible cultivars. There was a tendency for yellow rust to be more severe on early-sown crops. In 1975, eyespot was recorded on 11.8 per cent of the stems, 1.8 per cent of the symptoms being .severe. Fungicidal sprays were associated with a slightly smaller incidence of stem base diseases. Estimates of percentage loss in yield due lo particular diseases vary from almost zero caused by yellow rust in 1970 to 7.4 per cent loss caused by Septoria in 1972. [ABSTRACT FROM AUTHOR]