Disease Guide
University-rated fungicide efficacy, pricing per acre, and spray timing for eyespot (Aureobasidium zeae). Based on Crop Protection Network 2025 data.
Eyespot is a foliar disease of corn caused by the fungus Aureobasidium zeae (syn. Kabatiella zeae). It gets its name from the distinctive "eye-shaped" appearance of its lesions — small, circular spots with a tan center, dark brown to purple ring, and yellow halo. The disease is most common in the northern Corn Belt, particularly in Wisconsin, Minnesota, and northern Iowa.
Eyespot favors cool temperatures (60-75°F) and extended periods of leaf wetness from heavy dew, fog, or frequent rainfall. It is most prevalent during cool, wet growing seasons and typically appears in the vegetative stages (V6-V14). The fungus overwinters on infected corn residue, so continuous corn and reduced-tillage systems are at higher risk.
Yield impact from eyespot is generally minor. While severe infections can produce hundreds of small lesions per leaf, the cumulative effect on photosynthetic area is typically less than diseases like gray leaf spot or NCLB. Eyespot is most significant as a component of a multi-disease complex — when it appears alongside other foliar diseases, the combined effect can justify fungicide intervention even if eyespot alone would not.
Efficacy ratings from the Crop Protection Network 2025, based on multi-year university field trial data. Only products with tested ratings are shown — untested or not-listed products are excluded.
| Product | Mode of Action | Eyespot Rating |
|---|
Source: Crop Protection Network 2025. Ratings reflect multi-year, multi-location field trial performance.
Efficacy ratings cross-referenced with real purchase prices. Products sorted by efficacy rating — best performers first.
| Product | Eyespot Rating | Best $/Acre |
|---|
Prices as of early 2025 from AgChem, FBN, and Farmerceag. Actual pricing varies by geography, volume, and timing.
Standalone treatment is rarely needed. Eyespot is typically a minor disease that does not justify a dedicated fungicide application. If eyespot is the only foliar disease present, the economic return on a fungicide application is unlikely to be positive.
Incidental control from other applications. If you're already spraying at VT-R1 for tar spot, gray leaf spot, or NCLB, you'll get strong eyespot control as a secondary benefit. Most fungicides rate Very Good to Excellent for eyespot, so there's no need to choose products specifically for this disease.
Consider eyespot in the disease complex. When eyespot appears alongside other foliar diseases (gray leaf spot + eyespot, or NCLB + eyespot), the combined leaf area loss can push a borderline situation toward justifying a fungicide application. Assess the total disease load, not just individual pathogens.
Both triazoles and strobilurins work. Eyespot is well-controlled by products from both FRAC Group 3 (triazoles) and FRAC Group 11 (strobilurins). Even budget options like Tilt (propiconazole) rate Excellent for eyespot, making it one of the cheapest diseases to control if treatment is needed.
Efficacy ratings for all 26 products across 7 diseases, pricing from 3 suppliers, decision frameworks, and an ROI calculator.
View full guide →Search and filter 9,196 yield records from 867 university field trials by year, state, and crop.
Browse data →Fungicide ratings, pricing, and timing for tar spot (Phyllachora maydis).
View guide →Fungicide ratings, pricing, and timing for gray leaf spot (Cercospora zeae-maydis).
View guide →Fungicide ratings, pricing, and timing for NCLB (Exserohilum turcicum).
View guide →Fungicide ratings, pricing, and timing for southern rust (Puccinia polysora).
View guide →Fungicide ratings, pricing, and timing for anthracnose (Colletotrichum graminicola).
View guide →Fungicide ratings, pricing, and timing for common rust (Puccinia sorghi).
View guide →Based on Crop Protection Network 2025 data, the top-rated products for eyespot include Headline, Tilt, Xyway 3D, Proline 480 SC, and Quilt Xcel — all rated Excellent. Headline AMP also rates Excellent. Both triazole (FRAC 3) and strobilurin (FRAC 11) products perform very well against eyespot.
Eyespot produces small (1-4mm), circular lesions with a tan center, a dark brown to purple ring, and a yellow halo — giving them a distinctive "eye" appearance. Lesions are most visible when backlit. They typically appear scattered across the leaf surface and can be numerous but rarely coalesce like gray leaf spot or NCLB lesions.
Eyespot is generally a minor disease that rarely causes economically significant yield loss on its own. It is most common in cool, wet seasons and in the northern Corn Belt. While heavy eyespot infections can reduce photosynthetic area, the disease is typically overshadowed by more aggressive pathogens like gray leaf spot, tar spot, or NCLB. Standalone fungicide applications targeting only eyespot are rarely warranted.
Eyespot typically appears during cool (60-75°F), wet periods from V6-V14. It favors extended leaf wetness from dew, fog, or frequent rainfall. The disease is most common in the northern Corn Belt (Wisconsin, Minnesota, northern Iowa). Like most corn foliar diseases, eyespot is more prevalent in continuous corn and reduced-tillage fields where infected residue persists.
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