Monitor Pod and Stem Blight in Soybeans

Categories: HARVEST, SOYBEANS
Harvest is the time of year to check your soybean crop for signs of pod and stem blight, particularly fields for seed production. Check for signs of disease now because combining infected fields sooner rather than later helps reduce pod and stem blight pressure, especially when harvest is delayed due to wet weather. Pod and stem blight is caused by the Diaporthe and Phomopsis fungal disease complex, and it is found throughout most soybean producing areas of the U.S. 

Symptoms
  • The infection is only visible on dead plant tissue.
  • Stems develop linear rows of black specks, known as pycnidia, or fruiting structures.
  • Pods may be infected and show scattered pycnidia specks.
  • Infected seed appears shriveled, cracked and with a white, chalky mold.
 
Linear rows of pycnidia on the stem of an infected soybean plant. Source – Syngenta.

Development
  • Fungal pathogen overwinters on infected soybean or other crop residue.
  • Infection usually occurs early in the summer from water splashing spores onto the plant.
  • Symptoms don’t develop until the plant begins to reach maturity.
  • Disease symptoms are favored by warm, humid conditions at plant maturity.
  • Moisture at maturity plays a major role in disease development. The plant can be covered with pycnidia in wet years at maturity, whereas in dry years, pycnidia are confined to areas of the plant closer to the soil.
Management
  • Since the disease overwinters on infected crop residue, tillage and crop rotation will help reduce the infection. 
  • An R3 to R6 fungicide application, such as Trivapro®, can help mitigate disease and improve seed quality, but it is generally only recommended for soybean fields grown for seed. 
  • For the year ahead, UMN recommends planting high-quality, pathogen-free seed. When considering varieties for 2019 planting in affected acres, choose ones that are resistant to pod and stem blight.

Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.

Photos are either the property of Syngenta or used under agreement.

Syngenta hereby disclaims liability for third-party websites.
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