Influence of number and timing of fungicide applications on the yield and quality of early and later-sown spring malting barley grown in the south-east of Ireland

Eighteen experiments were carried out over a B-year period (1989-94) on thr ee different soil types to compare the effects of a broad-spectrum fungicid e, applied as 1-, 2- or 3-spray programmes at different growth stages, to c ontrol foliar diseases on early and later-sown Blenheim malting barley. Pow dery mildew, caused by Erysiphe graminis (Blumeria graminis) f. sp. hordei, was the dominant disease in all 6 years. Sowing date had a major effect on grain yield and ex-farm quality of the malting barley. The earlier-sown tr eatments gave significantly greater yield than the later-sown in 13 of the experiments, and significantly lower grain N concentrations and screenings (small grains < 2.2 mm) in 14 and 16 of them, respectively. Early and more frequent fungicide applications improved grain yield and red uced grain screenings but had no significant effect on grain N. Early-appli ed fungicide (i.e. before GS 33) was generally the most effective in contro lling disease, increasing yield and reducing screenings. The magnitude of t he response depended on disease severity. In those years when disease was l ow on the early-sown crops (1989, 1991 and 1994), the early-applied 1-spray programme and 2-spray programmes increased grain yields by relatively smal l amounts in both early and late-sown crops. In the other 3 years (1990, 19 92 and 1993), when disease severity was greater, the early-applied 1-spray programme and 2-spray programmes gave much greater grain yield increments o n both early and late sowings. The 3-spray fungicide programme gave the gre atest yields in most of the experiments but they were not significantly gre ater than the best of all the: other treatments. Grain screenings were redu ced by fungicide applications in both early and late-sown crops, but the ea rly-applied 1-spray programme and 2-spray programmes were generally the mos t effective in reducing screenings.