Controlling potato late blight with systemic-protectant fungicide combinations of metalaxyl and mancozeb |
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| Authors: | H W Platt |
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| Institution: | 1. Research Station, Agriculture Canada, C1A 7M8, Charlottetown, Prince Edward Island
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| Abstract: | Disease development was monitored weekly in field plots inoculated withPhytophthora infestans and treated with metalaxyl, mancozeb or metalaxyl/ mancozeb combinations. Late blight pressure was moderate to severe in 1981 and 1983 and was slight to moderate in 1982 and 1984. In 1982–84 all treated plots had significantly less foliar damage and late blight tuber rot than untreated plots. Use of metalaxyl alone resulted in the greatest increase in disease (up to 80% defoliation) in the latter part of the growing season. Under slight to moderate disease pressure, metalaxyl/mancozeb and mancozeb treatments provided significantly better disease control than metalaxyl. Under moderate to severe disease pressure, high levels of disease (65% defoliation) occurred by the end of the season with mancozeb and metalzxyl/mancozeb on 7- and 14-day spray schedules, respectively. However, significantly better control (about 20% defoliation) was obtained during early season, rapidly developing epidemic conditions when only three applications of metalaxyl/mancozeb were included in a 7-day mancozeb spray program. |
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