Anthracnose stem blight of soybean
Anthracnose stem blight is caused by the fungus Colletotrichum truncatum, and is generally a late season disease prevalent on maturing soybeans. Irregularly shaped red to dark brown blotches on stems and petioles can appear during early reproductive stages. Petiole infection can result in a shepherd's crook (curling or "hooking" of plant tissue). Near maturity, black fungal bodies that produce small, black spines and spores are evident on infected stems, petioles, and pods.
Warm, wet weather favors infection and disease development.
Crop rotation and tillage can reduce inoculum. Foliar fungicides made during the early to mid-reproductive growth stages can reduce disease, although there are limited situations where fungicide use targeting anthracnose stem blight will be profitable. Early anthracnose stem blight stem lesion. Image: D. Mueller
Shepherd's crooking of foliage is a symptom of anthracnose stem blight. Image: D. Mueller