Field Insights

Defeat Gray Leaf Spot in Corn This Season

Controlling gray leaf spot requires a combination of agronomic practices and proven fungicide applications.

Gray leaf spot is one of the most yield-limiting corn diseases in the Corn Belt. The pathogen that causes gray leaf spot, Cercospora zeae-maydis, thrives in extended periods of warm, humid weather. Its only known host is corn and it overwinters in crop residue. This makes gray leaf spot especially concerning for farms that operate with corn-on-corn planting and minimum tillage.

The University of Minnesota Extension describes the first sign of the disease as small, pinpoint lesions surrounded by yellow halos. Further along in development, lesions become long, narrow and rectangular, and can vary from brown to gray in color.

Growers can differentiate between gray leaf spot and Northern corn leaf blight by examining the underside of affected leaves. Unlike Northern corn leaf blight, gray leaf spot lesions are typically limited to the veined side of leaves.

Although scouting is a crucial part of disease management, the incubation period for gray leaf spot can be 27 days or more, so crops can be infected well before lesions appear in the weeks leading up to tasseling. This can lead to significant unexpected yield loss.

Severe gray leaf spot infections hinder photosynthesis and therefore decrease yields in two ways:

  1. University of Nebraska-Lincoln Extension research shows reduced photosynthesis limits the number of kernels produced by each ear.
  2. When corn plants can’t draw enough energy from the sun for grain-fill, starches are drawn from the stalks, which can increase lodging at harvest.

Proactive disease management is key to minimize the risk of damage and yield loss. There are several steps growers can take before finding gray leaf spot in their fields.

  • Plant tolerant hybrids. No current corn hybrids or inbreds have complete resistance to gray leaf spot, but some more tolerant hybrids can do well in moderate to high disease pressure.
  • Consider conventional tillage and crop rotation. This strategy can help reduce the amount of pathogen buildup in your fields.
  • Apply a reliable foliar fungicide with proven activity against gray leaf spot. Miravis® Neo fungicide delivers broad-spectrum preventive and curative control to protect corn yields and help boost your bottom line. Trivapro® fungicide delivers long-lasting residual control of gray leaf spot and other key diseases. Miravis Neo and Trivapro both also deliver plant-health benefits to help better preserve potential yield under high or low disease pressure.

A combination of these practices can help maximize yield and ROI potential even under heavy disease pressure. For more information about Miravis Neo, Trivapro and gray leaf spot, reach out to your local Syngenta representative or retailer.

June 2024 | By Syngenta Thrive / Design by Matt Rouse
  • Gray leaf spot is one of the top yield-reducing corn diseases in the Corn Belt.
  • The incubation period of gray leaf spot can be up to 27 days, meaning that corn is at risk of unexpected yield loss.
  • Miravis® Neo fungicide and Trivapro® fungicide both provide control of gray leaf spot to help minimize risk and yield loss.