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Study on the curative and eradicant action of fungicide combinations to control late blight in potato

Abstract

Commercial fungicide combinations were tested in the field for efficacy on foliar late blight caused by Phytophthora infestans in substitution of tin. When the first disease symptoms appeared, the tested fungicide treatments for late blight control were applied 3 times at 3-day intervals. The effect of the fungicide treatments on epidemic development, tuber rot and blight incidence and tuber yields were determined. Last summer late blight development was arrested in June due to high temperatures and lasting drought. August was characterized by rather low temperatures and high rainfall. These weather conditions were very favourable for the development of late blight. The foliar protection against P. infestans was comparable for all the tested fungicide combinations. The effect of combinations with dimethomorph + mancozeb (AcrobatC, 2.5 kg/ha) was less suppressive for P. infestans than the other fungicides tested. Lowest foliar disease severity was recorded in plots treated with fluazinam (Shirlan, 0.4 l/ha) + cymoxanil + chlorothalonil (Mixanil, 2 l/ha). Furthermore, highest tuber yield was noted in plots treated with fluazinam (Shirlan, 0.4 l/ha) + cymoxanil + chlorothalonil (Mixanil, 2 l/ha). The percentage blighted tubers fluctuated between 5 and 11 %. No fungicide combinations completely arrested epidemic development under the environmental conditions of the trial. However, fluazinam (Shirlan, 0.4 l/ha) + cymoxanil + chlorothalonil (Mixanil, 2 l/ha) controlled P. infestans most effectively

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