A new soybean disease in Rio Grande do Sul, Brazil

Abstract

An epiphytotic of soybean downy mildew (Peronospora manshurica (Naoum) Syd. ex. Gäuman) occurred in Rio Grande do Sul during the crop year 1968/1969. The disease was observed by the authors in fields, and these findings were confirmed in the laboratory. Information on the presence of the disease also was obtained in the soybean growing areas of the state. Based on an extensive review of literature about the disease and on the observations made during harvest, the authors discuss the possibilities of reducing or eliminating the harmful effects of the soybean yield. In their conclusions they suggest: breeding for disease resistance and research on seed treatment with fungicides; annual surveys of the incidence and intensity of attack of soybean diseases; expanding and intensifying field inspections and checking of seed production and sales; quarantine measures of importations; extension work in order to alert the farmers about the damage that may be caused by the disease; and deep plowing and covering of the crop residues to aid in the control of the disease.