Eyespot of Cereals

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Pathogen Facts

Eyespot of cereals is caused by the fungal organisms Oculimacula yallundae (wheat strain) and Oculimacula acuformis, (rye strain).
Disease development is favored by cool temperatures (44-55 °F) and wet leaf conditions (humidity, raindrops).
Eyespot is difficult to identify on younger plants, and infections are localized on a field by field basis.
Although the causative pathogens are not the same species, their management practices can be utilized interchangeably.

Photo - Variation in eyespot lesions on lower wheat stems.

Variation in eyespot lesions on lower wheat stems. Photo courtesy of Mary Burrows, Montana State University, Bugwood.org

Identification

Lesion development begins on lower stems near soil surface.
Perimeter of elliptical or eye-shaped lesions are dark brown, whereas the inside of the lesions are a yellowish-brown.
Lesions may contain darker pseudoparenchyma fruiting bodies.
White colored mycelium can be found in split stems.
Infected plants can have shrunken kernels due to interference with carbohydrate transport from girdled vascular systems.

Disease Cycle

Oculimacula yallundae and Oculimacula acuformis overwinter in crop residues, like straw.
Spores are dispersed from crop residue to new shoots by raindrop splash.
Spore germination infects the outer leaf sheaths before progressing inward to the vascular system, girdling the stem.
- Mycelial masses on the leaf sheaths form a black scurf that is often described as charred in appearance.
Girdled stems can weaken and lodge, reducing yield potential.

Photo - Closeup of eyespot lesion.

Close-up of eyespot lesion. Photo courtesy of Mary Burrows, Montana State University, Bugwood.org

Management Considerations

Early planting, higher seeding rates, and spring fertilizer applications can result in faster canopy closure, increasing humidity under the canopy and favoring pathogen development.
Although this pathogen overwinters on crop debris, spring tillage is not recommended because it can cause disease favoring pockets of moisture around the crowns of wheat.
Crop rotation away from wheat and barley can lower inoculum loads, but will not eliminate eyespot entirely due to the speed of inoculum buildup.
Burning crop reside is not effective or recommended to combat Oculimacula yallundae and Oculimacula acuformis.
Resistant varieties are available to combat eyespot of cereals.

Fungicides should be considered when 10% of the foliage is visibly infected.
Oculimacula yallundae and Oculimacula acuformis can be resistant to fungicides. Consult local agronomists and university extension to determine the best method for control.
Timing of fungicide application is critical, and should be done prior to stem elongation.

References

CAHNRS & WSU EXTENSION. (n.d.). Eyespot. Retrieved from Washington State University.
Hagerty, C., D.R. Kroese, C.C. Mundt,, A.F. Heesacker, and R.S. Zemetra, 2019. Eyespot of Wheat: How to identify and control this common fungal disease. Retrieved from OSU Extension Catalog.