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Causal organism - Pyrenophora tritici-repentis
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Wheat but can also attack barley, rye and some grasses.
Tan spot can be seed borne and infect seedlings, resulting in small tan to light brown flecks on young leaves. Symptoms are normally seen later in the season in the middle and upper canopy. First symptoms of infection are small tan to light brown flecks, with a chlorotic halo, often with a dark spot at the centre. Later these develop into light brown oval lesions with slightly darker margins with a light coloured spot at the centre. Under wet conditions the lesions produce spores which can make lesions darker in colour. Under ideal conditions these lesions coalesce to produce large areas of dead tissue.
