Effects of Fungicide Spraying on Brown Rust and Yield in Spring Barley

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Abstract
SUMMARY: In three field experiments in Cornwall in 1969–71, spraying 6–8 times with the fungicides zineb or oxycarboxin gave good control of severe attacks of brown rust (Puccinia hordei) in four cultivars of spring barley and increased the persistence of green leaf tissue. The disease developed late in the season, mainly after ear emergence, Other leaf diseases were slight, except for mildew (Erysiphe graminis) in 1971 in one cultivar. Spraying resulted in increases in grain yield ranging from 17 to 31 per cent and these were almost wholly due to increased grain weight (1000‐grain weight). One and two‐spray programmes of the fungicides gave only a partial control of brown rust and small yield increases. There was a statistically significant relationship between grain yield and brown rust recorded at growth stage 75 (11.1),* an increase of 10 per cent in brown rust on the second top leaf reducing yield by 7.7 per cent.