The plant develops reddish-brown lesions, which are similar to Phytophthora root rot damage but usually higher on the plant.
Stem canker lesions enlarge, turning brown to black and indenting slightly. Eventually they will surround the stem and cut the flow of water and nutrients in the plant. The result can be premature, and often sudden, plant death. Interveinal plant yellowing follows, with leaves dying but remaining attached to stems.
Wet weather aids stem canker development.
Description of Stem Canker
Soybean stem canker is caused by a soilborne fungus called Diaporthe phaseolorum.
The prevalence of stem canker depends on the amount of rainfall received during the early stages of soybean growth. The fungus produces many tiny spores on soybean debris, and the spores are carried by splashing rain to healthy soybeans.
Plants with stem canker are often first noticed in field areas where the crop stand is thin.
Life Cycle of Stem Canker
Stem canker infects soybeans in the early vegetative stages, causing symptoms as the plant enters the reproductive stages.
Stem canker often appears in the latter half of the growing season.
Management of Stem Canker
To manage this disease, plant varieties tolerant to stem canker and avoid extremely early planting, particularly in wet fields.
Rotate crops to break the stem canker cycle and limit overwintering opportunities.