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Stem Canker (Diaporthe phaseolorum var. caulivora)
Johnnie P. Snow
Louisiana State University (retired)
Stem canker has caused widespread damage in the southwestern United States in recent years. The disease can be very destructive because it kills plants from flowering to maturity. The fungus overwinters on diseased stems and infected seed. Initial symptoms are observed after flowering. The incidence of disease is greater in wet seasons.
Although symptoms vary on susceptible and resistant cultivars, the first symptoms are small reddish-brown lesions at the base of the branches or petioles. These lesions elongate, become sunken and may girdle the stem. Leaves exhibit an interveinal yellowing which becomes necrotic. Leaves on dead plants wither but remain attached.
The disease is controlled by using pathogen-free seed and planting resistant cultivars. Crop rotation will reduce overwintering inoculum.