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What is killing my lawn? It was fine in the spring, and now this summer, it is looking dead in patchy spots.

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There are several diseases that could be affecting your lawn during the hot summer months.  Brown patch (Rhizoctonia) causes irregular brown patches on the lawn.  Fading  (Curvularia sp.) also causes irregular dead areas.  Both of these diseases can spread rapidly during high temperatures, especially when turf is stressed.  Brown patch can infect the entire plant if conditions are suitable or can cause a crown and root rot.  Both pathogens survive on dead leaf blades and debris that reside in the thatch layer of the lawn.  

The best way to manage both diseases is to improve the health of your soil and turf.  When mowing during the hot summer months, keep the grass height at 2 ½" to 3" to alleviate stress.  Remove clippings to reduce sporulation on decayed leaves, and mow to a shorter height at your last mow in the fall, when the grass has stopped growing.  Fertilize only in the fall. 

An excessive thatch layer can contribute to disease development.  Thatch should be kept at ½ ″ thickness so that water and air can penetrate to the roots.  Aeration can improve air circulation to the root system.  Be sure to use an aerator that takes soil cores out of your lawn.  The machines that punch holes in your lawn only increase compaction.  This should be done in the spring or fall when the weather is cool and provides a less stressful environment for your turf to recuperate. 

Proper watering is very important.  Ideally, water your lawn deeply about once/week when natural rainfall does not occur.  Apply the water in the morning to allow the leaf blades to dry quickly. This reduces the moisture available for the fungus to develop and allows for better moisture retention in the soil.  Infrequent and deep watering promotes root growth which supports the crown and leaves. 

Posted on 22 Feb 2007

Marion Murray
Intergrated Pest Management Project Leader

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