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How To Scout for Physoderma Brown Spot and Stalk Rot in Corn

Categories: HARVEST, CORN
If you’ve received particularly wet weather this year, keep an eye out for Physoderma stalk rot. Scouting for the disease will help determine which remaining fields need harvested first. Physoderma stalk rot (PSR) is caused by Physoderma maydis, which also causes Physoderma brown spot (PBS) in corn. Physoderma can cause stalk rot and reduce yield. Prioritize harvesting fields with more than 10-15% PBS lodging to reduce standability issues.

Disease cycle and symptoms
  • More common in low tillage fields and continuous corn, where the pathogen can survive in soil up to 7 years.
  • Wind and rain disperse sporangia, or reproductive structures, on corn plants.
PSR SymptomsPBS Symptoms
Favorable under abundant rainfall and temperatures from 73-86° F.

Occurs when water is held in the plant whorl, where sporangia germinate and infect the plant with small lesions.
Dark purple to black spots show on lower stalk nodes where the infected plant will easily break. Dark purple to black oval spots appear down the leaf center and usually around stalk nodes.
PSR-infected plants often look healthy and grow large ears, and may never exhibit PBS signs.

Symptoms of PSR and PBS pictured above. At left, dark purple to black PSR spots appear near a lower stalk node. Shown right, dark purple to black oval PBS spots occur down the leaf center. Photo source: Dr. Alison Robertson, Iowa State University Extension and Outreach

Plant stresses and stalk rot
  • Severe PSR outbreaks have been prevalent in recent years across the Corn Belt, especially when wet weather is severe.
  • Lowered photosynthetic capacity causes the corn plant to move more sugars from the stalk to the ears, resulting in early maturity.
  • Roots and stalks lose pathogen resistance, allowing Physoderma stalk rot to thrive on early maturing tissue.
  • Over time, stalk strength weakens to the point of easily breaking at lower node, negatively impacting yield.
•    Since pressure largely depends on rainfall, anticipating disease management is difficult.
•    Reduce infection risk by rotating crops on fields with a disease history or on acres with poor drainage.
•    Crop rotation and tillage may help reduce disease pressure.
•    An R1 fungicide application such as Trivapro® may reduce disease severity and improve overall plant health. Trivapro fungicide is the hardest-working, longest-lasting fungicide for corn. With 3 active ingredients, including Solatenol® fungicide, Trivapro delivers long-lasting disease control and plant health benefits to maximize yield potential. 

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

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