The heat is on: Protect golf course turf during high temperatures

High temperatures will stress turfgrass in the next week. Here are simple reminders as the heat ramps up.

Syringing putting greens. All photos by Kevin Frank, MSU.

Syringing putting greens. All photos by Kevin Frank, MSU.

It’s already been a crazy weather year with unusually warm temperatures in February followed by more seasonable temperatures in March and excessive rainfall in April and May. June has started nicely, but the forecast for the next week is going to leave us and turf feeling oppressed, with high temperatures forecast in the high 80s and low 90s combined with high humidity.

Michigan State University Extension offers some simple reminders as the heat ramps up this weekend. 

Check the irrigation system

For the most part, irrigation systems have been resting this year as Mother Nature has blessed us with cool temperatures and adequate rainfall. Everyone has certainly used their irrigation system by this point in the year, but it might not be a bad idea to go out and actually observe the system operating in critical areas. Any inefficiencies, misaligned or malfunctioning heads may have been disguised by rainfall to this point, but that will not be the case in the next week.

Areas that reveal poor irrigation coverage first are typically edges of fairways, banks of greens, tees, bunkers and the rough. Many of these areas are also high traffic areas that are subject to compaction—another stress.

Syringing

In an effort to compensate for poor irrigation coverage and improve water management, hand watering is commonplace on golf courses. In Michigan, we are accustomed to syringing greens during periods of drought, but usually not fairways.

MSU Department of Plant, Soil and Microbial Sciences professor Joe Vargas has reminded me that in Mediterranean climates like southern Europe, where it does not rain from the middle of May until the middle of September and the temperatures are in the 90s every day, the superintendent will usually have three or more people assigned every day to syringe fairways. When we have similar conditions, it may become necessary to syringe fairways. We’re not necessarily talking about the hose crew, but rather a short irrigation cycle.

It is commonly perceived that noon is the warmest part of the day, when in reality it is often around 4 to 6 p.m. Syringing late in the afternoon might make the difference this year between healthy and heat-stressed turf.

Heat tracking

Heat tracks will be an issue on home lawns and golf courses. Anytime you put traffic from a cart, mower or spreader on turf that is nearing the wilting point or has already wilted, you will likely see a track in the following days or week. If possible, avoid mowing during the heat of the afternoon.

Wetting agents

Wetting agents are critical tools in the arsenal for alleviating localized dry spot. However, even with wetting agents, hand-watering may be necessary if it stays hot and dry.

Localized dry spot on turfgrass.

Localized dry spot on turfgrass.

Scout and plan for diseases

High temperatures will be accompanied by high humidity and warm temperatures at night. Conditions may become favorable for dollar spot, brown patch and even Pythium blight. Most superintendents treat for dollar spot and brown patch on a regular basis.

Pythium blight is not normally treated for on a regular basis in Michigan, but when daytime high temperatures are in the 90s and night temperatures above 70 degrees Fahrenheit following a rain, chances are optimal for a Pythium blight outbreak. If caught in time, the turf should recover from the dollar spot, brown patch and Pythium blight, which are primarily foliar diseases.

Crown rot anthracnose can also be a problem in warm weather on annual bluegrass greens, especially if the warm weather is accompanied by excess moisture from frequent rains. Widespread resistance of Colletotrichum cereale, the crown rot anthracnose fungus, to the benzimidazole and the Qo I fungicides has been reported.

Alternative fungicide chemistries should be used to control crown rot anthracnose. Adequate nitrogen fertility is also necessary to control this disease.

Summer patch is becoming an ever-increasing problem. The early 65 F and 75 F models for scheduling fungicide applications that worked so well for so many years have not worked that well recently in our research trials. We are now suggesting fungicide applications the first of June, July and August.

The products of choice should be the DMI fungicides and they should be watered into the top inch of the turf where the elongated crown of the turfgrass plant is located. If you can keep the crown of the plant healthy, the plant will survive no matter how many roots become infected.

Hydrate—drink plenty of fluids

Just a reminder to keep yourself hydrated during the hot weather. There are bound to be some long days and if you’re acclimated to temperatures in the 60s and 70s, temperatures in the 90s may cause us to wilt as much as the turf.

Dr. Frank’s work is funded in part by MSU’s AgBioResearch.

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