Numerous races of the pathogen have been identified, but cultivars with resistance to all races are available. Low, poorly drained fields with a history of Phytophthora should be avoided. The cause of SDS is unknown, but a Fusarium species has been implicated. Sudden death syndrome appears to be favored by the presence of soybean cyst nematodes, irrigation, and cool, wet weather. Losses can be high due to a reduction in pod number and seed size.
Symptoms first appear at flowering as yellow spots between the veins.
Severely diseased leaflets fall leaving the petioles attached to the plant. The root systems are reduced with a light brown vascular discoloration. Foliar symptoms of SDS are similar to stem canker. Sudden death syndrome can be distinguished from stem canker by the lack of a canker, the vascular discoloration, the white pith, and the dropping of severely infected leaves. Since the cause of SDS is uncertain, control measures are not available.