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Table 2. Field Fungi on Soybean Seed

Disease: Pod and stem blight and Phomopsis seed decay
Pathogen: Phomopsis sojae or Phomopsis longicolla
Symptoms: Pod and stem blight infected plants may be stunted and stems discolored. Black pycnidia or fruiting bodies of the causal fungi develop on the lower portion of the main stem, branches and pods as plants reach maturity (Fig. 1). The pycnidia may be limited to small patches of usually near the nodes or may cover dead stems and pods. On stems, the pycnidia are usually arranged in linear rows while on pods they are randomly scattered. Prolonged periods of warm, wet weather during flowering and pod fill favor the development of pod and stem blight. When conditions are wet late in the season the fungus may grow through the pod and infect the seed as well. Infected seed tends to be misshapen and moldy.

Disease: Purple seed stain
Pathogen: Cercospora kikuchii
Symptoms: Cercospora kikuchii can infect soybean seeds, pods, stems and leaves but is most commonly found on the seed. Infected seeds show a conspicuous discoloration varying in color from pink to pale purple to dark purple (Fig. 2). The discoloration may range from small specks to large blotches which cover the entire surface of the seed coat. Warm, humid weather favors disease development. Yields are usually not reduced but a high percent of seed stain may be evident at harvest.

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