COURSE CARE
Thatch Leads To Localized Dry Spot In Bentgrass Fairways August 14, 2012 By Brian Whitlark

(L) Localized dry spot is severe on these bentgrass fairways where thatch levels have accumulated over time. (R) Ideally, thatch depth in fairways should be maintained less than ¾ inch, but thatch in these bentgrass fairways has accumulated to nearly 2 inches (as indicated by the pitch mark repair tool).

On a recent visit to a golf course in New Mexico, the sand-capped fairways that once provided firm and fast conditions now produce soft, spongy surfaces as a result of thatch accumulation. Moreover, the thatch on top of the sand profile shows severe localized dry spot. This update provides a glimpse of how the benefits of sand capping can diminish when thatch accumulates to high levels and how this superintendent plans to improve conditions.

What thatch depth is considered excessive on bentgrass fairways?

On these fairways that were sand capped and formerly produced firm conditions to play on, thatch depth has accumulated to approximately 2 inches (photo). Ideally thatch depth is maintained between 3/8 inch to 3/4 inch in bentgrass fairways.

What are the implications of the excessive thatch?

The fairways are soft and spongy, are prone to scalping and have developed localized dry spot (photo). Although salt levels are not high enough to result in turf injury at this time, elevated salts were measured in the thatch when compared to the profile underneath. Should the salt level increase in the irrigation water, salinity in the thatch may increase above the tolerance levels for bentgrass.

How is this superintendent addressing the situation?

A large piece of equipment was purchased that is able to verticut and vacuum simultaneously.  This machine is robust enough to verticut deeply without any struggles and leaves behind only minimal cleanup (photo’s). Plans are in place to verticut deeply from 3-4 times per season, weather permitting. This superintendent is considering running the verticutter in two directions during weather periods where recovery is optimal to maximize thatch removal.

How do you remedy the localized dry spot?

A variety of wetting agents are currently being utilized to minimize localized dry spot, but the efficacy of such applications are thought to be compromised due to the excessive thatch. Once thatch levels are reduced, it is likely the wetting agents will offer more effective and repeatable results.

For more tips on combating thatch, localized dry spot and additional agronomic strategies, please do not hesitate to contact Mr. Pat Gross: pgross@usga.org  or Mr. Brian Whitlark: bwhitlark@usga.org, or call the Southwest regional office at (714) 542-5766.