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Agronomic Crops Network

Ohio State University Extension


Corn Disease

C.O.R.N. Newsletter Articles

  1. Author(s): Pierce Paul , Author(s): Francesca Rotondo

    Tar spot is beginning to show up in a few corn fields across the state, but based on some of the samples received and questions asked, there is still some uncertainty about the correct diagnosis or identification of this disease, particularly during the early stages of its development. When fully developed, the stromata are easy to see and feel on the surface of leaves (or ear husks later in the season) as slightly raised black spots resembling sprinklings of tar that give the disease its name.

    Issue: 2023-26
  2. Figure 1. Gray leaf spot
    Author(s): Stephanie Karhoff, CCA , Author(s): Jason Hartschuh, CCA , Author(s): Pierce Paul

    A dry early June delayed disease progression in corn, but we have received reports of gray leaf spot (GLS), tar spot, and to a lesser extent, northern corn leaf blight (NCLB) after recent wet, humid conditions. Corn growth and development is variable across Ohio, ranging from VT to R3 (“milk” stage). Continued scouting is needed, especially in fields with susceptible hybrids and a history of foliar diseases. Scouting efforts should also focus on continuous-corn, no-till fields, since fungal pathogens causing disease can overwinter on crop residue.

    Issue: 2023-26
  3. Author(s): Taylor Dill , Author(s): Laura Lindsey , Author(s): Osler Ortez , Author(s): Stephanie Karhoff, CCA , Author(s): Luke Waltz

    Episode 21 of Battle for the Belt is now available:     

    Issue: 2023-25
  4. Gibberella ear rot in corn
    Author(s): Jason Hartschuh, CCA , Author(s): Pierce Paul

    Ear rots and mycotoxins: Ear rots are beginning to show up in pockets across the state, leading to concerns about mycotoxin contamination of grain. So far, we have received images and samples with Gibberella, Diplodia, Fusarium, and Trichoderma ear rots, four of the most common ear rots in the state. Of these, Gibberella (GER) and Fusarium ear rots are of greatest concerns, since grain harvested from affected fields will be contaminated with mycotoxins, particularly vomitoxin in the case of GER.

    Issue: 2022-34
  5. Author(s): Pierce Paul

    Most of the corn across the state of Ohio is now between the late-R1 (silking) and late-R3 (milk) growth stages, with a few late-planted fields at late vegetative stages. Concerns about tar spot, but more likely, a sense of security provided by relatively high grain prices have led to several fields being sprayed with a fungicide at or shortly after R1 and questions being asked about spraying additional fields that are now at mid reproductive stages (between late-R2 [kernel blister] and R3 [milk]) of development.

    Issue: 2022-27


  1. Abnormal Ear Diagnosis Poster,  ACE-1. Farmers frequently encounter abnormal corn ears in their fields when the crop has experienced a major stress, such as drought, temperature extremes, disease, insect injury, or misapplied chemicals. These abnormalities often affect yield and grain quality adversely. In this poster, ten abnormal corn ears with distinct symptoms and causes are highlighted. The purpose of the poster is to help corn growers and agricultural professionals diagnose various ear disorders.

  2. Corn Disease Management in Ohio, Bulletin 804. Five to 15 percent of Ohio's corn crop is lost to disease each year, amounting to nearly $100 million in lost farm income. Corn diseases include seedling diseases, leaf blights, stalk rots, ear and kernel rots, and viruses. This bulletin describes the disease symptoms, provides color images, gives the environmental factors favoring the disease, the method of transmission and infection, and management options for the major diseases affecting corn in Ohio.

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