Relationship between spraying schedule of fungicides and occurrence of Cercospora leaf spot of sugar beet in 2000
2002
"Watanabe, H. (Nippon Beet Sugar Manufacture Co. Ltd., Sapporo (Japan)) | Hayasaka, M. | Funahashi, S. | Kawashima, T. | Nagashima, S. "
"Cercospora leaf spot of sugar beet occurred heavily throughout Hokkaido in 2000. Large difference was often observed in the level of disease occurrence among neighboring fields. Growers of each of 33 locations were divided into two groups, a severely damaged ( group H ) and a lightly damaged group ( group L ). Then they were investigated as to the spraying schedule, kind of fungicides used, root yield and sugar content. The rate of decrease in root yield and sugar content of group H was higher than that of group L in 2000, comparing with that in an average year ( 1993-1999 ). It then was supposed that the difference of decreasing rate was due to the difference of disease severity between two groups. Average number of spraying was 3.8 for the group H and 4.1 for the group L. In terms of fungicides, DMIs was used in about 50% of sprayings and Mancozeb or Kasugamycin and copper were used in the rest of sprayings for the both groups. Since a little difference was observed in the number of sprayings and kind of fungicides between two groups, it was estimated that spraying schedule was most significant for the occurrence of the disease. Examination of disease control measures revealed that the group L started spraying always earlier than the group H, and obviously used DMIs during the period of disease development. It was concluded that early and timely spraying of DMIs were apparently effective in controlling the disease."
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