WSU Extension


Lawn and Turf
2,4-D damage 
Anthracnose/Basal crown rot 
Brown blight 
Brown patch 
Curvularia blight (Fading out) 
Dog injury 
Dollar spot 
Fairy ring and mushrooms 
Leaf spot 
Microdochium patch (Pink snow mold) 
Necrotic ringspot 
Powdery mildew 
Pythium crown and root rot 
Red thread 
Septoria leaf spot (Tip blight) 
Slime molds 
Take-all patch 
Typhula blight (Gray snow mold) 
Yellow patch 
Chinch bugs 
European Chafer 
European crane fly 
Japanese beetle 
Japanese beetle 
Sod webworm 

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Caption: Thatch
Photo by: R.S. Byther
Lawn and Turf : Thatch
(revision date: 6/22/2015)

Thatch is a layer of plant debris which generally accumulates at the soil surface. It consists primarily of undecomposed stem, crown, and root materials. Grass clippings contribute little to thatch formation. In healthy lawns, thatch decomposition rates balance grass growth, resulting in relatively little accumulation. However, excess fertilization, overwatering, and improper mowing will aid thatch accumulation. Also, acid soils may result in reduced thatch decomposition rates. Thatch in excess of 1/2" should be removed, as it can prevent water penetration. Crowns and roots can develop in the thatch rather than in the soil, making frequent watering necessary and making lawns more prone to drought injury. Certain types of grass naturally develop more thatch. Creeping bentgrasses produce large amounts of thatch, and are not recommended for home lawns.
Management Options

Non-Chemical Management
  • Provide adequate fertilization.
  • Deep, infrequent watering encourages deep root growth.
  • Soil aeration may be necessary to improve water penetration.
  • Remove thatch as necessary, preferably in early spring, using a power rake or by hand. Work in two directions (i.e. N-S, then E-W), removing 1/2 of the total desired amount in each direction. Reseed as needed.
  • Mow regularly at recommended height.
  • For more information on proper lawn care see EB0482E, Home Lawns.
Select non-chemical management options as your first choice!

Chemical Management

None recommended


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Caption: Thatch
Photo by: R.S. Byther