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Category: Environmental Stress

Management Guides to Reduce Winterkill in Warm-Season Turfgrasses

Posted on by Teresa Roberts

By Ross Braun, Ph.D., Kansas State University 

It is September, winter is coming, now is the time to think about strategies to reduce winterkill risks in your warm-season turf. Last winter (2024-2025) was a tough one on some of our warm-season turfgrass managers. There were extensive reports of winterkill in zoysiagrass and bermudagrass areas on golf courses and sports fields in Kansas, Missouri, and many other areas in the transition zone. Winterkill injury is not easily identified until the warm-season grass is finished greening up in the spring (usually mid-to-late May in KS). At which point, you notice dead turf areas that never greened up with no active growth (Figure 1). What also didn’t help this spring was the below-average temperatures in May, with slightly below-normal precipitation amounts at the same time. This slowed down the spring green-up of our warm-season turfgrasses (zoysiagrass, bermudagrass, and buffalograss) and delayed the recovery needed in some areas, so that it did not start until mid-June or later. These winterkill risks will always be present, and some years we unfortunately see it more than others, but I still think warm-season turfgrasses are a solid choice for turfgrass managers in the transition zone because we can reduce a lot of management inputs (water, fertilizer, pesticides, mowing) compared to growing cool-season turfgrasses.

Over the past two years, my colleagues at other universities and I have collaborated to create “management guides” for bermudagrass and zoysiagrass managers, especially those in the transition zone that experience greater risks of winterkill. You will likely recognize that the authors include many familiar names of turfgrass scientists, as well as the wealth of knowledge they bring to these articles. These guides are written to help you identify potential vulnerable areas, the causes of winterkill, and offers solutions to prevent and recover from winterkill. I encourage you to check out these articles; they are both “open access,” meaning the authors have already paid for them to be freely available to the public (not behind a paywall). You can read them online or download each as a PDF to read on your computer or phone. I hope these management guides assist in decision-making and help to reduce potential winterkill risks in warm-season turfgrass systems.

Management strategies for preventing and recovering from zoysiagrass winterkill https://doi.org/10.1002/cft2.70050

Management strategies for preventing and recovering from bermudagrass winterkill https://doi.org/10.1002/cft2.20302

 

Figure 1. Increased winterkill in West Lafayette, IN, in 2018–2019 in low-lying, poorly drained areas. The site was ‘Meyer’ zoysiagrass (Zoysia japonica Steud.) maintained as a golf course fairway. The photo was taken on May 24, 2019 by Aaron J. Patton.

Wet Spring will Likely Lead to Quick Drought Response as Summer Approaches

Posted on by Teresa Roberts

By Jack Fry, Professor and Commercial Turf Extension Specialist

Frequent rainfall reduces the necessity for grasses to produce deeper roots, and also enhances more shoot growth.  As summer approaches and an extended period of time without rainfall occurs, drought stress will be occurring more rapidly that it sometimes has.

Uniform irrigation is important so that water is distributed nicely over a lawn, golf course, sports field, or other area.  In addition, you can estimate the amount of water that has been lost from the turf over time, which is called evapotranspiration (ET).  Evapotranspiration includes water evaporation from the soil and transpiration from the leaves.  Here is a site from Kansas State University that provides weather information and allows you to determine the level of ET that has occurred:

https://mesonet.k-state.edu/

You can click on the location near you on the KS map when this website comes up.  Then, go to the upper left corner of mesonet (click on the 3 lateral bars) and select any information desired.  To determine water use, go to weather – historical weather – enter the dates that are of interest for you.  After doing so, click submit and you’ll see weather details returned.  On the far right of the image, click on grass ET and you’ll see an estimate of ET for that area.  Here’s an example of the ET that I looked at for Olathe, KS:

The ET that you see is based upon a formula called Penman-Monteith, which uses temperature, humidity, solar radiation, and wind to create the estimate.  As a reminder, the ET that you view is based upon assumption that the soil moisture is high.  In other words, as soil dries down in a turf area, the ET is likely going to be lower than estimated on this site.  That said, this information is useful to provide guidance on the amount of irrigation that may be needed to apply to the turf area. To confirm the amount of water applied from your irrigation system, use a sprinkler gauge that indicates the amount of water applied for a given amount of time.

Deeper, less frequent irrigation will enhance rooting as time progresses.   To do this, you may desire to wait until you begin to see wilt occurring on the turf.  As an alternative, you can determine what the soil moisture measurement is when wilt is just beginning and irrigate just prior to that soil moisture level.  As summer heats up and less rainfall begins, it is quite likely that following this strategy will still require irrigation be applied often due avoid extensive wilt.  It is possible that over time, irrigation frequency can be reduced.

There are number of different research articles below that demonstrate all turf species can get enhanced rooting with a deeper, less frequent irrigation strategy.

Tall Fescue:

Huang, B. and J. Fu.  2001.  Growth and physiological responses of tall fescue to soil surface drying.  Intl. Turfgrass Soc. 9:291-296.

Fu, J., J. Fry, B. Huang.  Tall fescue rooting as affected by deficit irrigation.  HortScience 42:688–691. 2007.

Creeping Bentgrass:

Fu, J., P. Dernoeden.  2009.  Creeping bentgrass turf response to two summer irrigation practices: rooting and soil temperature. Crop Sci. 49:1063-1070.

Jordan, J.E., R. H. White, D.M. Vietor, T.C. Hale, J.C. Thomas, and M.C. Engelke.   2003.  Effect of irrigation frequency on turf quality, shoot density, and root length density of five bentgrass cultivars.  Crop Sci. 43:282-287.

Zoysiagrass:

Qian Y. and J. Fry.  1996.  Irrigation affects zoysiagrass rooting and plant water status.  HortScience 31:234-237

Above is the photo from the zoysiagrass research noted above in 1996 (a number of years ago). The zoysia on the left had been irrigated daily for an extended period of time and then water was turned off.  On the right, zoysia had been irrigated deeply and infrequently (based upon ET measurement) and then water was turned off.  Obviously, the deeper, infrequent irrigation enhanced its tolerant to drought.

Thinking Ahead to Factors that Can Impact Freeze Injury of Warm-Season Grasses

Posted on by Jack Fry

 

Winter injury in certain areas where warm-season grasses grow in the transition zone is not unusual.  Specifically, here are the things that can have a significant impact on winter injury of zoysiagrass and bermudagrass:

 

 

 

  • Selection of a less cold hardy warm-season grass: There is a relatively short list of bermudgrass and zoysiagrass cultivars that are best adopted to the transition zone, including Kansas. Here are a few of each of those species that are relatively good through winter, but that doesn’t mean they can’t suffer winter injury:

Zoysiagrass – Meyer, Innovation, Zenith (seeded), Chisholm

Bermudagrass – Tahoma 31, Latitude 36, Northbridge, Yukon (seeded), Monaco (seeded)

 

  • High Nitrogen levels: High levels of nitrogen fertilizer through the growing season, or nitrogen applied in the fall can have a more significant impact on winter injury.

 

  • Shade: Shade reduces photosynthesis and carbohydrate production by grasses, and can significantly reduce the potential for a species/cultivar to survive cold temperatures.  Trimming trees or removing them may be required to enhance cold hardiness.

 

  • Traffic: Significant traffic on the soil and turf prior to winter can have a significant impact on the turf and result in higher levels of winter injury.  Traffic control (not allowing excessive traffic) and effective aerification can help enhance its survival.

 

  • Excessively wet soil: It’s not unusual for warm-season turf that sits in a low area (often on golf course fairways) where water accumulates can have a greater impact of winter injury.  High levels of water in the soil will impact these grasses when severe cold arrives.  Improved drainage can help protect these areas.

 

  • Lack of snow cover: Snow is very beneficial to protect warm-season grasses prior to excessively low temperatures.  For example, several years ago we had snow cover in Olathe, KS when temperatures were at least -15 F and no winter injury occurred.

 

  • Grass not fully acclimated for cold temperatures: There is a greater chance of freezing injury if temperatures get quite low when the grass had not fully acclimated to cold. Example – excessively low temperatures in November or December can have a significant impact.  Likewise, the same may occur during late winter or early spring when warmth approaches and then that is followed by excessive cold.

 

  • Exposure to wind on high level areas: This can often cause desiccation in winter if exposed to strong wind when there is no snow cover.  If expected in the near future, it may be useful to apply water on these elevated areas before the excessive cold arrives.  Or…some type of cover to protect the surface.

Wet Spring will Likely Lead to Quick Drought Response as Summer Approaches

Posted on by Teresa Roberts

By Jack Fry, Professor and Commercial Turf Extension Specialist

It’s been a wet spring through much of Kansas.  In Olathe, KS there has been 11.3 inches from March 1 to June 10.  Frequent rainfall reduces the necessity for grasses to produce deeper roots, and also enhances more shoot growth.  As summer approaches and an extended period of time without rainfall occurs, drought stress will be occurring more rapidly that it sometimes has.

Uniform irrigation is important so that water is distributed nicely over a lawn, golf course, sports field, or other area.  In addition, you can estimate the amount of water that has been lost from the turf over time, which is called evapotranspiration (ET).  Evapotranspiration includes water evaporation from the soil and transpiration from the leaves.  Here is a site from Kansas State University that provides weather information and allows you to determine the level of ET that has occurred:

https://mesonet.k-state.edu/

You can click on the location near you on the KS map when this website comes up.  Then, go to the upper left corner of mesonet (click on the 3 lateral bars) and select any information desired.  To determine water use, go to weather – historical weather – enter the dates that are of interest for you.  After doing so, click submit and you’ll see weather details returned.  On the far right of the image, click on grass ET and you’ll see an estimate of ET for that area.  Here’s an example of the ET that I looked at for Olathe, KS:

The ET that you see is based upon a formula called Penman-Monteith, which uses temperature, humidity, solar radiation, and wind to create the estimate.  As a reminder, the ET that you view is based upon assumption that the soil moisture is high.  In other words, as soil dries down in a turf area, the ET is likely going to be lower than estimated on this site.  That said, this information is useful to provide guidance on the amount of irrigation that may be needed to apply to the turf area. To confirm the amount of water applied from your irrigation system, use a sprinkler gauge that indicates the amount of water applied for a given amount of time.

Deeper, less frequent irrigation will enhance rooting as time progresses.   To do this, you may desire to wait until you begin to see wilt occurring on the turf.  As an alternative, you can determine what the soil moisture measurement is when wilt is just beginning and irrigate just prior to that soil moisture level.  As summer heats up and less rainfall begins, it is quite likely that following this strategy will still require irrigation be applied often due avoid extensive wilt.  It is possible that over time, irrigation frequency can be reduced.

There are number of different research articles below that demonstrate all turf species can get enhanced rooting with a deeper, less frequent irrigation strategy.

Tall Fescue:

Huang, B. and J. Fu.  2001.  Growth and physiological responses of tall fescue to soil surface drying.  Intl. Turfgrass Soc. 9:291-296.

Fu, J., J. Fry, B. Huang.  Tall fescue rooting as affected by deficit irrigation.  HortScience 42:688–691. 2007.

Creeping Bentgrass:

Fu, J., P. Dernoeden.  2009.  Creeping bentgrass turf response to two summer irrigation practices: rooting and soil temperature. Crop Sci. 49:1063-1070.

Jordan, J.E., R. H. White, D.M. Vietor, T.C. Hale, J.C. Thomas, and M.C. Engelke.   2003.  Effect of irrigation frequency on turf quality, shoot density, and root length density of five bentgrass cultivars.  Crop Sci. 43:282-287.

Zoysiagrass:

Qian Y. and J. Fry.  1996.  Irrigation affects zoysiagrass rooting and plant water status.  HortScience 31:234-237

Above is the photo from the zoysiagrass research noted above in 1996 (a number of years ago). The zoysia on the left had been irrigated daily for an extended period of time and then water was turned off.  On the right, zoysia had been irrigated deeply and infrequently (based upon ET measurement) and then water was turned off.  Obviously, the deeper, infrequent irrigation enhanced its tolerant to drought.

Pine Problems in Kansas

Posted on by Teresa Roberts

By Judy O’Mara, Diagnostician, K-State Plant Disease Diagnostic Lab

It was pretty cold in mid-January 2024, the low temps in January sent me to the K-State Mesonet (https://mesonet.k-state.edu/weather/historical/) to take a closer look at the weather patterns during that time period. The Mesonet is a collection of weather stations across Kansas that can be used in a variety of ways but my favorite is to take a look BACK in TIME at the historical weather patterns. The temperature dropped pretty low on Jan 14th (-10.5F) and Jan 15th (-10.6F) in Manhattan, KS. Brrr.

In any given year, it is not uncommon to see extreme weather patterns impact plant growth and health. Winter damage to pine trees frequently shows up on the north or northwest side of the tree, although it can hit the top of the tree as well. Winter damage can hit multiple trees or can show up on scattered trees within a planting. The outer needles tend to be scorched with the inner needle growth remaining green. The more exposed foliage is more susceptible to desiccating winter winds. Winter damage on pine trees can be confused with some common Kansas pine diseases such as pine wilt, Diplodia pine tip blight and Dothistroma needle blight.  One tip that can help to differentiate between these problems is the TIMING of the damage. Pine trees generally enter the winter looking good and then get hit by low temperatures and/or desiccating winds sometime between December-February. A look at the K-State Mesonet can help pinpoint the weather event that caused the damage.

Winter damage can look pretty dramatic but it is best to wait until early to mid-May to assess recovery potential. Even though the pine needles are scorched, the dormant buds frequently escape damage and push out new growth in the spring. The damaged needles eventually shed and the overall appearance of the tree will gradually improve. Another quick way to check recovery potential is to pop off a few buds at the end of the branch and see if they are still green inside.

Winter damage can be confused with some common Kansas pine diseases. For help sorting out these problems reach out to your local county extension office. The K-State Plant Disease Diagnostic Lab can also provide assistance.  https://www.plantpath.k-state.edu/extension/plant-disease-diagnostic-lab/

Winter Desiccation

Posted on by Teresa Roberts

By Dr. Jack Fry, Professor and Commercial Turf Extension Specialist

Winter desiccation on a creeping bentgrass green that had significant thatch accumulation.

Winter desiccation is a form of “winter injury” that can often occur in February and March during extended periods of dry weather. Most susceptible are seedlings that were seeded late in autumn, and established turf that has excessive thatch. If you seeded in late October and turf is not yet mature, consider applying water if we get into an extended dry period.  Lack of maturity means limited root growth and more frequent water is needed.

Creeping bentgrass is quite susceptible to desiccation, particularly when it accumulates some thatch.  In fact, winter desiccation injury often more common on fairway height turf that has accumulated thatch compared to that growing on putting greens.  Roots become elevated in the thatch and are unable to absorb water from soil.  Creeping bentgrass growing on elevated sites that are most exposed to wind is most susceptible.  Again, water application may be needed during extended dry periods to reduce the risk of desiccation.  This may required methods of water application other than just irrigation.  For example, sometimes boom sprayers are used to deliver water – multiple passes may be needed.  In areas where desiccation is common on bentgrass greens, it not unusual for superintendents to topdress heavily in the fall, or provide some kind of cover on the surface through winter – sometimes synthetic cover or using branches from cedar trees or other evergreens –  to help reduce wind effects.  Click links below for more information.

USGA article

Sportsfield Management article

 

Pushing Snow

Posted on by Cheryl Boyer

Many of you are busy “pushing snow” with the recent cold weather, and there will likely be more snow to push in the next couple of months. Please take a few minutes to train your staff on protecting ornamental plants when clearing hard surfaces like parking lots.

While clearing the lot, driveway, or sidewalk is the most critical objective, “do no harm” should also be a goal. Far too many plants are crushed by the push and weight of snow in winter months. Sometimes, the mystery summer problem is actually a clear winter problem.

There is a tendency to pile snow on top of green spaces in parking lots. However, plants in those spaces continue to need to photosynthesize (evergreens) and exchange gases and are likely to die or suffer severe dieback if the cold weather persists and the snow takes a significant time to melt. Piling snow in planting areas can also contribute to soil compaction and root decline, causing problems later in the growing season.

De-icing chemicals are often mixed into snow that is pushed into landscape settings. As the snow melts, it dumps salt into the planting area, damaging shoots and roots for the long term. To minimize the landscape impacts of clearing snow, consider alternative de-icing salts like calcium chloride and calcium magnesium acetate and follow the label instructions when possible. Sand can also help provide traction.

With your staff, practice identifying an appropriate place to pile snow that isn’t in landscape areas, offers a place to collect runoff, and won’t result in slush that can splash onto plants. When possible, make these decisions before snow is on the ground—snow can cover a lot of detail and make it easy to lose track of the areas that need to be preserved.

Study each site individually and develop a plan for human, pet, and plant safety when winter storms hit to avoid problems in the future and establish trust with your clients.

Summary of Extreme Temperatures

Posted on by kennelly

By Megan Kennelly, KSU Dept of Plant Pathology

We have all been feeling the heat lately. I hope everyone has been staying safe and hydrated.

Just how hot has it been? The KSU Mesonet weather team provides a helpful summary here with interesting perspectives and historical context:

https://eupdate.agronomy.ksu.edu/article_new/a-hot-day-for-the-record-books-in-kansas-august-19-2023-559-8

 

 

Here is one of their maps – click the above link for additional data and figures. Source: Kansas Mesonet https://mesonet.k-state.edu/

Historic Dry Spells Lead to Tree Stress: Help Ensure Your Trees Are Healthy Enough to Handle It

Posted on by Teresa Roberts

By Jason Griffin, Professor, Extension Specialist

Extension personnel across the state have been answering questions about dying/dead trees and shrubs since early spring. Symptoms have ranged from dead, to partially dead, to unusual growth, and late leaf emergence. While it is always good to scout for damaging insects (bagworms anyone?), disease pathogens, and physical injuries such as repeated mower damage to the trunk or recent construction projects that compromised root systems, this year we can blame a lot on our old friend mother nature. Since late summer 2022 through May 2023 rainfall has been scarce, a hard freeze came early, and summer heat exposed any weak landscape plants.

The National Weather Service office in Wichita (@NWSWichita) describes the
period from July 1, 2022 to April 23, 2023 as the 5th driest in history and the driest since 1989. Under those conditions, trees fail to accumulate adequate carbohydrates for the approaching winter, making them more susceptible to winter injury.

As drought continues through winter and spring, trees lack adequate moisture required for new spring growth. The result is trees failing to leaf out in the spring or pushing new spring growth that looks abnormal. If the plants were compromised by pests or physical injuries, environmental stress effects are magnified.

Trees do have mechanisms to deal with elevated temperatures. Unfortunately for the plants, heat rarely occurs as a single isolated event, and it is impossible to talk about heat without mentioning its partners in crime. As seasonal temperatures rise, precipitation becomes less frequent (or absent). Additionally, the Kansas wind machine gets fired up and cloud cover becomes less abundant.  This quadruple whammy reduces a plant’s ability to tolerate elevated temperatures. Trees and shrubs use transpiration to cool themselves. When soil moisture is lacking, transpiration is reduced, thereby exacerbating the issue. If the situation does not improve, long-term damage can occur. What we see now are the effects of months of drought, a cold winter, and summer heat.

Of course, most plants made it into 2023 with little noticeable difficulties, attesting to their resiliency. What can be done to reduce the stressors that lead to tree decline?

Winter Injury Noticeable on Warm-Season Grasses

Posted on by Jack Fry

Winter injury has shown up in Kansas and many other states on some warm-season grasses, including bermudagrass and zoysiagrass.  Low temperatures came in mid-December at levels that were not common for warm-season grasses to deal with when they have not reached maximum cold acclimation.  For example, daily low temperatures did not exceed 10 F between Dec. 22nd and 27th in Olathe, KS. In addition, little or no snow cover was out to help protect turf and wind speed was high (approached 30 mph during this period in Olathe) which could have caused desiccation damage as well.  Temperatures during this period reached a low of -7 F.  Winter injury has also been reported in Oklahoma, Texas, and Arkansas on both bermuda and zoysia.  Injury tends to be most common in areas that have high levels of traffic, shade, or excessive thatch.  There are also many different “micro-climates” across areas that can result in different levels of injury – from excessive to none.

‘Latitude 36’ bermuda experienced winter injury at the Olathe, KS Horticulture Center.

Injury on a Z. matrella variety in KS.  Varieties of this species tend to me more cold sensitive.

 

 

 

 

 

 

 

 

 

Winter injury on zoysia cultivars in the National Turfgrass Evaluation Program in Olathe. Those damaged are Z. matrella cultivars, used primarily in the southern U.S.

‘Meyer’ winter injury on golf course fairway with north-facing slope.