Also known as yellow leaf spot, red smudge
Pyrenophora tritici-repentis (Died.) Drechs. [teleomorph]
Drechslera tritici-repentis (Died.) Shoemaker [anamorph]
- Symptoms: At first, lesions appear as tan to brown flecks, which expand into large, irregular, oval- or lens-shaped tan blotches with a yellow or chlorotic margin (see picture). As these spots coalesce, large blotches are formed. The development of a dark brown to black spot in the center of the lesion is characteristic of the disease. As the disease progresses, entire leaves, spikes, and even whole plants may be killed.
- Development: Initial infections come from diseased crop debris in the soil, or from diseased grass hosts. Usually the lower leaves are infected first, and the disease progresses to the upper leaves and leaf sheaths if conditions are favorable. This disease develops over a wide range of temperatures and is favored by long periods (18 hours or more) of dew or rain.
- Hosts/Distribution: Tan spot can affect wheat and several related grasses; triticale, barley, and rye are less frequently affected. The disease is found in the major temperate wheat-growing areas.
- Importance: When severe, tan spot can cause premature death of the leaves, thereby reducing yield by lowering test weights and producing a high degree of kernel shriveling. This disease has become more important with the increased adoption of minimum and/or no-till agronomic practices, which leave crop debris in place.
For extended information click here