Heat Stress

The following is an article from the GCSAA that helps explain what heat and humidity do to the turf and the management practices that we alter or eliminate during these periods.

Prolonged periods of high temperatures – and in some cases excessive rainfall – and high humidity can make life uncomfortable for golfers and golf courses alike, with Mother Nature holding all the cards for true relief.

“The simple fact is the cool-season turfgrasses such as bentgrass, fescue, bluegrass, annual bluegrass (Poa annua) and others are stressed when temperatures climb and humidity is high," Bob Randquist, CGCS, and president of the Golf Course Superintendents Association of America, said. "Golf courses in many parts of the country experience this every year, however what can make the situation so dire is the high levels of extended heat and humidity, and the sizeable part of the country affected (Midwest, Mideast, Northeast and Mid-Atlantic). We are already seeing this is an issue that could potentially match the conditions of last year."

Why heat stress is so difficult on golf course turf

According to Randquist, golf facilities and those entrusted with managing the golf course – golf course superintendents – are not alone in this battle with the elements. However, the nature of their product makes their challenge greater.

"Certainly homeowners, athletic fields and businesses suffer turfgrass damage brought on by these kinds of conditions," Randquist said. "What makes it more difficult for golf facilities are the mowing heights are much lower and traffic is much heavier. That just adds to the stress on the turfgrass."

Randquist indicates that golf course superintendents are addressing the issue with a variety of management practices to make sure turfgrass survives. While there may be some short-term impact on playability of the course, the alternative is the loss of grass, the closure of the course and the additional costs of re-establishing playing surfaces (primarily putting greens).

He also cautioned golfers from thinking that water, whether from rain or irrigation, is the answer to the ills. There is a difference between heat stress and drought stress. Adequate irrigation will alleviate drought stress. Adequate irrigation will not alleviate heat stress. It is not only possible, but likely, for a turfgrass plant to be adequately watered and still suffer from heat stress under extended periods of high temperatures.

Managing turf under heat stress

Randquist indicated that during periods such as this, it becomes easy to compare golf course conditions and pressure decision makers into actions that might prove detrimental to the long-term health of the playing surface. "We know the weather conditions will become more agreeable. What is important right now is to manage the golf course in a manner so that turf can be kept alive until that point. Relying on the expertise of the golf course superintendent and understanding the focus in on the long term is the best guide for facilities."

Among the practices that superintendents are implementing to manage golf courses include:

• Raising the mowing heights of playing areas, most notably putting greens.
• Alternating daily practices of mowing and rolling putting greens, with consideration to skipping a day if the schedule of play allows.
• Forgoing double mowing, topdressing, verticutting or grooming greens.
• Watering to provide adequate soil moisture, but not over watering, as saturated soil will cause the turfgrass to decline rapidly.
• Hand watering as much as feasible. If a green has a dry spot or two, superintendents will hand water the dry spots only and will not water the entire green. When the entire green shows stress from a lack of water, superintendents use the overhead sprinklers and water the entire green.
• Avoid aerifying using large diameter tines that penetrate deeply into soil and remove a core of soil. If a superintendent feels the putting surface is sealed, venting using small diameter solid tines or other similar technique is employed.
• If fertilizer is required, small amounts of fertilizer are applied via a sprayer and observation of the response occurs before fertilizing again.
• Monitoring and adjusting golf car traffic patterns to minimize stress to turf.