Thatch and Mat
Problems of Turfgrass

Curtis E. Swift, Ph.D.
Colorado State University Extension
Tri River Area


What is Thatch?

Thatch is an intermingled organic layer of dead and living shoots, stems and roots that develops between the green vegetation and the soil surface. Thatch has a high lignin content and resists microbial breakdown.

What is the difference between thatch and mat

Mat is thatch intermixed with mineral matter. Thatch may be transformed into a mat as a result of top dressings or when turf grown on a flood plain becomes covered with silt due to flooding. Like thatch, mat develops between the green vegetation and the soil surface. Mat develops on putting greens and other areas of turf that have been top dressed. Golfers often describe the feel of mat as a `cushion'.

Does thatch or mat cause problems?

Insects that Inhabit Thatch
Hairy Chinch Bug Blissus leucopterus hirtus Montandon Southern Chinch Bug B. insularis Barber
Bluegrass webworm Parapediasia teterrella (Zinck.) Corn root webworm Crambus caliginosellus Chem.
Larger sod webworm Pediasis trisecta (Wlk.) Pretty crambus Microcrambus elegans (Clem.)
Silver barred lawn moth Crambus sperryellus Klots Striped sod webworm Fissicrambus mutabilis (Clem.)
Black cutworm Agrotis ipsilon (Hufnagel) Variegated cutworm Peridroma saucia (Hubmer)
Bronze cutworm Nephelodes minians Guenee Armyworm Pseudaletia unipuncta (Haworth)
Fall Armyworm Spodoptera frugiperda (J.E. Smith) Lawn Armyworm S. mauritia (Boisduval)
Fiery Skipper Hylephila phyleus (Drury) Bluegrass weevils Hyperodes spp.

Thatch and mat increase the turfgrass's susceptibility to heat, cold and drought stress by encouraging the growth of the grass crowns, rhizomes and roots in these layers losing the protection of the soil. The more thatch and mat, the greater the tendency for scalping the turf.

Are there any benefits from thatch or mat?

A moderate level of one-quarter to one-half inch thickness has the following advantages:

Causes of Thatch and Mat

Thatching tendency of Turfgrass
High
Medium
Low
Zoysiagrass Kentucky bluegrass Perennial ryegrass
Bermudagrass Creeping bentgrass Tall fescue
Creeping red fescue Hard fescue Buffalograss
Chewings fescue

Do grass clippings contribute to thatch?

In a word - NO!

Research shows that turf clippings are from 85 to 95 percent water. During the summer months these leaves decompose quickly leaving nitrogen and other beneficial nutrients for the turf. Clippings remaining on the lawn in the fall may not decompose until warmer weather returns in the spring.

Plant parts differ in cell wall content, with roots, rhizomes and stolons containing the greatest levels of lignin and are resistant to decomposition. Leaf blades contain cellulose and hemi-cellulose that are readily broken down by microbes. Grass clippings contain little lignin.

Grass clipping should be left on the lawn because:

The removal of grass clippings to help control crown- or root-rot diseases is not effective, as collecting clippings has little effect on inoculum levels of such disease organisms.

How do I know if my lawn has a thatch or mat problem?

What can be done about thatch?

The following steps can be taken to help reduce thatch accumulation. Keep in mind that reducing thatch is a long-term process and must be accomplished over several years. Thatch and mat prevention and correction is not an occasional practice. It requires proper turf management to correct the balance between accumulation and decomposition of thatch.

Should you dethatch your lawn

One researcher answers this question by asking how much weight you gained during the winter. Vargas suggests that if you gained a lot of weight, the exercise of running the power rake might be good for you. But, if you are out of shape, it might kill you. He continues by explaining that this process does little but remove winter-killed grass that will breakdown anyway, but you will not remove the thatch or correct a thatch problem.

Gardeners who hand rake or power rake in the spring normally only collect the grass clippings that did not decompose the previous fall. A power rake that is set to cut deep enough to remove thatch is often quite injurious and disruptive to the turf. Core aerating while removing less thatch causes less problems.


reference gif References Used:

Ali, A.D. & C.L. Elmore. 1989. Turfgrass Pests. Extension, University of California, Division of Agriculture and Natural Resources.
Koski, A. 1995. Turfgrass Management - Master Gardener Training. Colorado State University Extension.
Beard, J.B. 1986. Thatch. Grounds Maintenance, November, pages 36-40
Couch, H.B. 1995. Diseases of Turfgrasses: Third Edition. Krieger Publishing Company, Malabar, Florida.
Erusha, K.S. & T. P. Riordan. Thatch Prevention and Control. 1990. NebGuide G85-751, Extension, University of Nebraska-Lincoln
Koski, A. and C. Wilson. E.A.S.Y.* Lawn Mowing: Environmental Action Starts in your Yard. Colorado State University Extension and United States Environmental Protection Agency, Region VIII, Denver Colorado.
Shearman, R.C., A.H. Bruneau, E.J. Kinbacher, and T.P. Riordan.Thatch Accumulation in Kentucky Bluegrass Cultivars and Blends. 1983. HortScience 18(1):97-99.
Shurtleff, M.C., T.W. Fermanian & R. Randell. 1987. Controlling Turfgrass Pests. Prentice-Hall, Inc. Englewood Cliffs, N.J.
Tashiro, H. 1987. Turfgrass Insects of the United State and Canada. Cornell University Press.
Vargas, J.M., Jr. 1994. Management of Turfgrass Diseases; Second Edition. Lewis Publishers


Placed on the Internet August 26, 1996

Comments should be addressed to
Dr. Curtis E. Swift, Area Extension Agent, Horticulture
Colorado State Extension
2775 US Hwy 50, Grand Junction, CO. 81503
voice: 970-244-1840
fax: 970-244-1700

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