EFFICACIES OF FUNGICIDES IN CONTROLLING SPOT BLOTCH OF BARLEY

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Abstract
Efficacies of 12 fungicides in inhibiting growth of Bipolaris sorokiniana on potato dextrose agar and development of spot blotch symptoms in barley leaf segments inoculated with B. sorokiniana were examined. Efficacies in growth inhibition were high (EC95 [effective concentration of active ingredient (a.i.) for 95% inhibition], 2-40 ppm) for RH-2161, fentin hydroxide, thiram and carbathiin; intermediate (EC95, 250-500 ppm) for triadimefon, anilazine, captafol and dodine; and low (EC95; .gtoreq. 1000 ppm) for captan, chlorothalonil, mancozeb and metiram. In symptoms inhibition assays, RH-2161 was extremely effective (EC95, 70 ppm), and anilazine, chlorothalonil, fentin hydroxide, mancozeb, triadimefon and captafol were highly effective (EC95, 150-300 ppm). Efficacies of foliar applications of 6 fungicides in controlling spot blotch and promoting yield of barley in the field were also examined. Triadimefon, RH-2161 and fentin hydroxide were applied at 0.25 kg a.i./ha and chlorothalonil, anilazine and mancozeb at 2 kg a.i. ha-1 at barley growth stages 8, 10.1 and 10.4 (Feekes'' scale). Disease severity was significantly reduced in barley treated with mancozeb, RH-2161, chlorothalonil, fentin hydroxide, triadimefon and anilazine by 63, 68, 68, 77, 82 and 88%, respectively, compared to checks. All fungicides except chlorothalonil significantly increased 1000-kernel weights of treated plants in the range of 11-15%. Anilazine, triadimefon and RH-2161 performed better than other fungicides evaluated in the field.