National Institute of Food and Agriculture, U.S.Paul, MN: The American Phytopathological Society. This will allow the spores to be observed, which are fusoid, uni-septate, and two-celled. If pycnidia are present in the leaf blotches, they can be removed with a needle, mounted under a cover slip in water, and crushed by applying light pressure. Also, maintaining adequate amounts of nitrogen without excessive fertilizer application has shown to be helpful. Irrigating early to knock off the dew and irrigating deeply and infrequently (without causing stress) can help control this disease. Mowing a grass species at the recommended height is important along with maintaining sharp clean mowing blades when trying to avoid spread. Mowing – Maintain grass recommended height for species is a cultural practice that tends to help the spread of Ascochyta blight. Cultural practices such as mowing, irrigation, and fertilizing can be important factors in managing disease outbreaks. For this reason, fungicides are rarely recommended for control. Frequent mowing, particularly during leaf wetness periods can encourage disease spread.Īscochyta blight is a common occurrence on grasses in many parts of the world, including the United States, Great Britain, Europe, Russia, Mexico and South America.Īlthough conspicuous, Ascochyta blight is generally not a severe disease that causes permanent damage. Leaf wetness events such as periods of high humidity, heavy dew events and frequent irrigation favor disease occurrence and spread. The pathogen enters through cut leaf tips caused by mowing and grows toward the leaf base. The pycnidia release conidia during wet periods, which are transferred to uninfected leaves through splashing or mechanical dispersion. The leaf lesions are circular or elliptical, usually white or brown in color, and may develop red or thin off-brown borders.Īscochyta survives as mycelium and pycnidia in debris. Individual leaves die back from the tip when infected. A uniform or localized blighting results in a bleached, chlorotic stand symptom that is loosely aggregated in the landscape. The disease is most commonly observed and conspicuous on Poa pratensis L. rarely infect the crown of the turfgrass plant and cause permanent damage. Conidia are hyaline to pale yellow colored, uni-septate, and fusoid. The outer most layer of the pycnidial wall is rust sepia colored with the inner layers hyaline. Pycnidial wall is stromatic with many layers of cells. They are more common in groups and are more dominant on the upper leaf surface. Pycnidia are 70 – 200 μm in diameter and yellow brown, rust brown, or brick red. Ascochyta blight of turfgrass has been associated with a number of Ascochyta spp., which are dothidiomycetes.
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