Surveys of diseases of spring barley in England and Wales, 1976–1980

Abstract

SummarySamples from 200–300 randomly selected spring barley crops were taken annually at growth stage 73–77 (milky ripe) from 1976 to 1980. The number of samples from each region was proportional to the area of barley grown in each region. The percentage of the area of the top two leaves affected by diseases was recorded. Mildew (Erysiphe graminis) was the most widespread and severe disease recorded. Brown rust (Puccinia hordei) and rhynchosporium (Rhyn‐chosporium secalis) occurred frequently but at relatively low levels. Yellow rust {Puccinia striiformis) and septoria (Septoria nodorum) were seen on less than 50% of the samples in most years, and halo spot (Selenophoma donacis) and net blotch (Pyrenophora teres) were rarely recorded. There was an association between the severity of rhynchosporium and the number of rain days in May and June. The highest levels of brown rust occurred in the south and east and rhynchosporium was more common in Wales and the south‐west than in the east, but there were no differences in the regional distribution of other diseases. Cultivar resistance, sowing date, previous cropping and fungicide usage were all found to be associated with altered disease levels. The proportion of crops treated with a foliar fungicidal spray rose from 26% in 1976 to 47% in 1980. The use of tridemorph declined but that of triadimefon increased reaching 29% of crops treated by 1980. The use of ethirimol as a seed treatment declined from 16% of crops grown from treated seed in 1976 to 7% in 1980. Estimated yield losses between 1976 and 1980 varied between 4% and 9% due to mildew, between 0.3% and 0.8% due to brown rust and between 0.2% and 0.5% due to rhynchosporium.