However, seeds infected with downy mildew can be mistaken for white mold-infected seeds, and such a misidentification occurred many times during the 1997 planting season. The pathogen also can survive in crop residues. Aphids are the vectors that spread the disease during a growing season. The dry summer this year may have favored the development of this disease. However, this discoloration should not be considered as a reliable indicator of SMV because other stresses can cause such mottling.
Seed testing is necessary to determine the presence of the infection.
Phomopsis species and Anthracnose species were frequently isolated from premature, dying plants after mid-August of this year. Typical symptoms were bright yellow leaves on the top of the plant followed by death of tissues from the top down. These two fungi can be seedborne. Seeds infested with Phomopsis may be cracked and shriveled and usually have a low germination rate. If these seeds are used, they may result in low emergence or seedling blight.