Controlling Leaf Blight in Your Lawn

In Spring on June 10, 2013 at 9:29 pm | Written by green-admin

The weather in the St. Louis area is warming up but the wet conditions along with the heat create the right environment for leaf blight.  This fungal disease attacks Kentucky bluegrass and fine fescue during warm, damp or humid weather that is typical of late spring and late summer.  Leaf blight causes large patches of a lawn to become discolored which many homeowners wrongly diagnose as chemical burn or heat stress.  It is important to be able to identify leaf blight damage in order to control the situation.


The main warning sign of leaf blight is bleached, straw-colored turf in uniform patches that can vary greatly in size.  Damage from leaf blight can be distinguished from heat stress or chemical burn by the bleached leaf tips of the grass blades.  Leaf blight causes grass blades to die or wilt from the tip down and can even leave hour glass shaped lesions on the blades.


Leaf blight thrives in warm, moist weather typical of the late spring and early fall, but it can also be a problem through the summer as well if humidity levels are high.  The fungus that causes leaf blight is the most active at temperatures between 60 and 80 degrees.  While the weather is undoubtedly a factor in the occurrence of leaf blight, these actions may also contribute to its development:

  • Excessive watering
  • Mowing when the lawn is wet
  • Mowing with dull blades which tears the grass


Dry weather conditions are usually enough to cause leaf blight to disappear but it will leave the lawn substantially thinner.  If prolonged periods of humidity or wet conditions persist, then leaf blight may last further into the summer and require action to alleviate the problem.  Here are the three best strategies for controlling leaf blight:

  • Aeration: Removing excess thatch and reducing soil compaction through aerations can help prevent the disease.
  • Fertilization: A healthy, strong root system is a lawn’s best defense against all diseases and proper fertilization is the best way to maintain a strong root system.  Fertilizer with adequate nitrogen levels can help damaged lawns recover from thinning caused by leaf blight.
  • Proper Mowing and Watering: Practicing good mowing and watering techniques will minimize turf stress and leave your lawn less vulnerable to diseases.  Watering should only be done in the morning hours if the rain fall is insufficient and mowing should be done when the grass is dry with a sharp mower blade.
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