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Causal organism - Oculimacula yallundae and Oculimacula acuformis (formerly Tapesia species)
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Wheat, barley, oats, rye and many grass species.
In late autumn and early spring, eyespot symptoms are very difficult to distinguish from those of the other stem base diseases caused by sharp eyespot and fusarium. Frequently all that is visible is a brown smudge on the leaf sheath at the stem base. If crops are early-sown eyespot lesions may penetrate one or two leaf sheaths, making identification more conclusive. Lesions caused by fusarium and sharp eyespot are frequently confined to the outer leaf sheath. Later in the season eyespot symptoms become more distinct and appear as an eye-shaped lesion with a dark margin, usually below the first node. Later still, the margin of the eyespot lesion is often dark and diffuse with a central black 'pupil' occasionally visible. When severe attacks of eyespot occur, whiteheads are commonly seen scattered through the crop. The effects of eyespot on plants is often very much more severe if plants are also suffering from take-all. Moderate levels of both diseases, which alone may not produce obvious symptoms, can produce premature ripening with whiteheads. The whiteheads frequently become colonised by sooty moulds later in the season, producing severe blackening of the ears.
