Physoderma Stalk Rot and Brown Spot in Corn

Categories: HARVEST, CORN
Though harvest 2018 is entering the home stretch, keep an eye out for Physoderma stalk rot if you’ve received particularly wet weather this year. Scouting your fields for signs of disease will help determine which remaining fields need to be 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 fields with more than 10-15% PBS lodging to reduce standability issues.

Disease cycle and symptoms
  • More common in low tillage fields and in continuous corn where the pathogen can survive in the soil for up to 7 years.
  • A combination of wind and rain disperse sporangia, or reproductive structures, onto corn plants.
PSR Symptoms
PBS Symptoms
Abundant rainfall and temperatures from 73-86°F are favorable conditions for PSR.

Development occurs when water is held in the plant whorl, where the sporangia germinate and infect the plant with small lesions.
PSR results in dark purple to black spots around lower stalk nodes where the infected plant will break easily. 
Dark purple to black oval spots occur down the center of the leaf and usually around stalk nodes.
Plants with PSR often look healthy with large ears, and may never exhibit signs of PBS.

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Symptoms of PSR and PBS are 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 center of the leaf. 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, crown and stalk lose resistance to pathogens, allowing stalk rot diseases such as Physoderma stalk rot to thrive on early maturing tissue.
  • Over time, stalk strength weakens to the point of easily breaking at lower nodes and negatively impacts yield.
Management
•    Disease management is difficult to anticipate since pressure is largely dependent on rainfall.
•    To reduce the risk of infection, avoid planting corn hybrids in fields with a history of infection or on acres that drain poorly.
•    Crop rotation and tillage may help reduce disease pressure.
•    A fungicide application such as Trivapro® at R1 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.

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

Syngenta hereby disclaims liability for third-party websites.

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