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Pod and Stem Blight: Kentucky Soybean IPM

Pod and Stem Blight


Symptoms

Seeds infected with pod and stem blight produce diseased seedlings that frequently become blighted and die. Generally, pod and stem blight is first observed occurring on fallen petioles near the base of attachment or on stems just above petiole attachment.

pod and stem blight
pycnidia on stem

Tiny black specks (pycnidia) can be observed, usually arranged in rows, on the stems and leaf petioles of older infected plants.

Infected pods will also have scattered pycnidia and pods may be poorly developed. Infected seeds will be shrivelled, cracked, and may be encrusted with a white fungal mass. Seed may be internally infected and show no symptoms.

blighted pods and seeds

Pod and stem blight has little effect on crop yield, but seed quality can be greatly affected. The disease is principally of concern to soybean seed producers.

Pod and stem blight can be confused with anthracnose. Warm, humid weather favors the development of both diseases. Occurring late in the season, both diseases frequently occur together on the same plants.

Cause

Pod and stem blight is caused by various specious of the fungi Diaporthe and Phomopsis. The fungi survive the winter in both infected seed and crop residue. Infected crop residue can lead to high levels of pod and stem blight in fields. Seed infection occurs only if pods become infected. Pod infection can occur any time starting at flowering, but extensive seed infections will not take place until plants have pods that are beginning to mature (R7 growth stage).

Damage to pods by insects will favor the development of both pod and seed infections. Early maturing soybean varieties and early plantings tend to be affected more than later maturing cultivars and late plantings. This is because the early maturing and early plantings mature during more disease- favorable conditions than the late maturing and late plantings. Delayed harvest can significantly increase pod and stem blight in both early- and late- maturing cultivars.

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References and Additional Information


This site was created and is maintained by Pat Dillon, Department of Entomology, University of Kentucky, S-225 Agricultural Science Ctr North, Lexington, KY USA  40546-0091 (phone: 859/257-3571). Please send questions or suggestions to: pdillon@uky.edu