Eyespot Disease in Corn

Northern areas of the Midwest Corn Belt are affected by the fungal pathogen that causes eyespot in corn. The disease pathogen, Aureobasidium zeae, overwinters in corn residue and is found in higher concentrations in no-till and conservation tillage systems. Corn on corn rotations can also increase the potential for eyespot appearing in corn. Favorable conditions for disease development include conservation tillage with infected residue, lack of resistance in corn products, and prolonged periods of cool, wet conditions.

Identifying eyespot in corn can be accomplished by inspecting corn leaves during the mid-vegetative to R1 corn growth stages. Look for small circular water-soaked lesions that can turn into tan spots that become surrounded by brown to purple rings complete with a yellow halo that looks much like an eye (Figure 1). Common and southern rust lesions are similar in size to eyespot but are raised above the surface where eyespot is flat on the leaf surface. This disease can also be confused with insect feeding damage; however, if no insects are present and the classic halo is present then eyespot is most likely the culprit. Disease progression starts in the lower canopy and works its way up as the corn nears maturity. Similar to Goss’s Wilt, backlighting an affected leaf, mid- or late season is a diagnostic tool because the lesions are visible even after the leaf dies. These lesions can appear in patches on a corn leaf and can progress to a point where the lesions join and affect large portions of the leaf surface. Disease onset can occur as early as the mid to late vegetative growth stage all the way to maturity in corn. Earlier infections with prolonged periods of cool wet conditions can reduce photosynthetic efficiency which increases the chances of yield reductions.

Eyespot management in corn can include residue management such as tillage and crop rotation to help reduce inoculum load, planting eyespot resistant corn products, and in the case of severe infection that could affect yield, fungicides applied at R1 corn growth stage have shown good efficacy at preserving yield potential in corn infected with eyespot. As with all pesticides, before deciding to use a fungicide it is best to contact your local extension office for Integrated Pest Management (IPM) guidelines and include economics in your decision to spray a fungicide. When diseases show up uninvited in your fields, look no further than your local Channel Seedsman to help diagnose the issue and help get your crop back on track.

Channel Agronomist
John Goeden

Sources:

Jackson, T. and Ziems, A. 2009. Corn disease update: Eyespot confirmed. CROPWATCH. University of Nebraska-Lincoln. https://cropwatch.unl.edu/corn-disease-update-eyespot-confirmed/.

Strunk, C. 2022. (Updated from Byamukama, E.) Southern rust, bacterial leaf streak, and eyespot are developing in corn. South Dakota State University Extension. https://extension.sdstate.edu/southern-rust-bacterial-leaf-streak-and-eyespot-are-developing-corn/.

Eye spot. Extension & Outreach. Department of Crop Sciences. University of Illinois. http://extension.cropsciences.illinois.edu/fieldcrops/corn/eye_spot/.

Malvick, D. 2018. Eyespot on corn. University of Minnesota Extension. https://extension.umn.edu/corn-pest-management/eyespot-corn/.

Wise, K., Mueller, D., Sisson, A., Smith, D., Bradley, C., and Robertson, A. 2016. A farmer’s guide to corn diseases. The American Phytopathological Society.

Websites verified 4/17/23. 1221_444551