Eyespot of Wheat

Eyespot of Wheat


Eyespot occurs on wheat grown in North and South America, Europe, Australia, New Zealand and Africa. In the United States the disease is most common in the Pacific Northwest. It occasionally occurs in the Great Plains and can easily be mistaken as take-all because of the similarity of symptoms. Eyespot has at least two other common names, foot rot and strawbreaker. The disease is caused by Psedocercosporella herpotrichoides (Fron) Deighton (teleomorph Tapesia yallundae Wallwork & Spooner). The fungus infects cereals including wheat, oats, barley and rye as well as many grasses. Eyespot is most severe where continuous wheat is grown and the climate is cool and moist. Disease severity is greater on winter than on spring cereals. The fungus overwinters as mycelium on crop debris or on fall seeded crops. Winter survival on debris decreases dramatically when residue remains on the soil surface. Conidia are produced in late winter or early spring. The optimum conditions for sporulation are temperatures between 47oand 54oF and humidity close to 100% near the soil surface. Conidia are water-splashed to the crown and basal culm or foot area of the plant. Roots are not infected. Spores germinate and invade coleoptiles and leaf sheathes directly or through stomata. The fungus grows through the leaf sheath and into the culm. Mycelium may be present inside the culm. Conidia are also formed on external tissue four to 12 weeks after primary infection. Secondary conidia and the infections they incite are not important in disease development during the current season but initiate the disease cycle for the following season. Eyespot tends to be more severe when winters are mild and springs are cool. Early seeding and dense canopies also favor disease development. The fungus becomes dormant when temperatures are greater than 16oC and the atmosphere becomes dry.

Symptoms


Typical eyespot lesions are most commonly visible after jointing but may be seen on younger plants. Lesions are initially seen as lens shaped areas on the leaf sheath. The center of the lens is white or tan and the margin is brown. The pointed ends of the eye are oriented longitudinally on the lower stem, 4 cm above or below the soil line. Lesions extend into the culm with age and black stroma-like clumps of mycelium form in the center. The mycelial clumps resemble tiny pieces of charcoal. Stems may be girdled when lesions expand in girth. The lower stems shrivel, and plants lodge random directions. Large areas of plants lodge when the disease is severe. In cases of light infections or when infected plants are some distance from each other, affected tillers are supported by healthy ones and lodging does not occur. Heads on affected tillers may be small, poorly filled and mature early, producing white heads.

Plant Health Management

References

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Caveat

This description is presented for information only and no endorsement is intended for products listed, nor criticism meant for products not mentioned. Always consult the product label before purchasing and using any pesticide.

Material contained on the Links from the page are the responsibility of the linked page's author(s).

This page was researched and drafted by: Jane Christensen, Department of Plant Pathology, University of Nebraska-Lincoln

Disease images were provided by: Dr. David Wysong, Department of Plant Pathology, University of Nebraska-Lincoln

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This page is authored and maintained by:
Dr. J.E. Partridge, Department of Plant Pathology, University of Nebraska-Lincoln

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Copyright (C) 2003 J.E. Partridge, University of Nebraska-Lincoln. All Rights Reserved.