The Heat is On!

Posted on June 29th, 2018

Dr. Kevin W. Frank and Dr. Joe Vargas, Jr.
Michigan State University
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With temperatures forecast into the 90’s and heat indices into the 100’s, this weekend is going to leave not only us but the turf feeling oppressed. 

1. Check the Irrigation System

This may seem obvious but it might not be a bad idea to go out and actually observe the irrigation system operating in critical areas. Any inefficiencies, misaligned, or malfunctioning heads may have been disguised by cooler temperatures or rainfall to this point, will not be in the next week. Areas that reveal poor irrigation coverage first are typically edges of fairways, banks of greens, tees, and bunkers, and the rough.  Many of these areas are also high traffic areas that are subject to another stress, compaction.

2. 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. Dr. 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 90’s every day, the superintendent will usually have 3 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 later in the day around 4 to 6 p.m. Syringing late in the afternoon might make the difference this year between healthy, heat stressed turf.

3. 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.

4. Wetting Agents

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

5. Scout and Plan for Diseases

High temperatures will be accompanied by high humidity and warm night-time temperatures. 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 day time high temperatures are in the 90’s and night temperatures above 70°F 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 (CRA) can also be a problem in the warm weather on annual bluegrass greens especially if the warm weather is accompanied by excess moisture from frequent rains. Wide spread resistant of Colletotrichum cereale, the CRA fungus, to the benzimidazole and the Qo I fungicides has been reported. Alternative fungicide chemistries should used to control CRA. Adequate nitrogen fertility is also necessary the control this disease.

Summer patch is becoming an ever-increasing problem.  The early 65 and 75-degree 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. If you can keep the crown of the plant healthy the plant will survive no matter how many roots become infected.

6. Hydrate

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

Dr. Frank’s and Dr. Vargas’ work are funded in part by MSU’s AgBioResearch.

This article was published by Michigan State University Extension. For more information, visit To have a digest of information delivered straight to your email inbox, visit To contact an expert in your area, visit, or call 888-MSUE4MI (888-678-3464).

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