Ascochyta Leaf Blight

June 3, 2018
  • Ascochyta

Ascochyta Leaf Blight

Ascochyta leaf blight is a common but minor turfgrass disease plaguing Kentucky bluegrass, perennial ryegrass, tall and red fescues, and bentgrasses. It can be attacked by one of several species of the fungus Ascochyta. Extended periods of wet weather or frequent watering; followed by wet conditions or drought-stressed turf can cause Ascochyta. It survives in the thatch and infects grass leaves during periods of rain. The fungus enters through freshly cut leaf ends and grows toward the base of the leaf. Frequent mowing, particularly with a dull mower, increases infection. Ascochyta can appear quickly; your lawn could look flawless, but can be blighted overnight.

Ascochyta blight may cause large areas of turf to be blighted or it may appear only in localized patches. Individual leaves die back from the tip and take on a bleached color. When the disease occurs in localized patches, it somewhat resembles dollar spot except that the individual lesions do not have reddish-brown margins. When a turf is uniformly infected, it resembles the injury from a dull mower blade.


Injury from Ascochyta blight is seldom extensive so control measures are rarely necessary. No fungicides are registered for use specifically against it; however, most broad spectrum turfgrass fungicides will provide some protection.

General weekly and yearly lawn practices can help to manage the disease. When Ascochyta is present, it is best to reduce mowing frequency and increase your mowing height. Do not mow when your turf is moist as it will provide more opportunity for infection. Regular fertilization helps to stimulate the growth of grass. The quicker the grass grows, the quicker the disease will grow out on its own. Thatch can be reduced by a yearly core aeration; this can allow for better water penetration in the future.

It is important to remember that the blight will not kill your lawn; it will grow out within a few weeks. Your lawn simply needs to heal and grow on its own using the tips mentioned here.