5/20/2024

As summer approaches, the focus of golf course superintendents shifts from spring Greenup to maintaining high-quality turf that can withstand summer stress. But as you know, there are many prevalent issues that come with the change of season. Here are 10 tips to keep your turf in top shape through the growing season.

1. Provide adequate fertility

Malnourished turf will not have the energy required to withstand and recover from summer stress. Providing adequate nitrogen and supplementing other nutrients as needed to prevent deficiencies will improve turfgrass stress tolerance and recuperative potential. Disease epidemics often increase in severity under deficient nitrogen conditions in both warm and cool season turfgrasses (Dant et al., 2020, Hempfling et al., 2014).

2. Incorporate Seaweed Extract and Fulvic Acid

Seaweed extract, fulvic, and humic acids are research-proven tools to enhance turfgrass stress tolerance and promote root growth. Seaweed extract protects photosynthetic efficiency during stressful growing conditions. Humic and Fulvic acids are excellent chelating agents that promote root growth and soil micronutrient availability.

Research has demonstrated a combination of seaweed extract and humic acid is more effective in promoting stress tolerance and root growth than applying either material alone (Schmidt et al., 2003). Application should begin in the spring before the onset of heat stress. Both materials are more effective when applied preventatively before heat stress has set in.

3. Adjust Mower Setup

Meeting green speed expectations and maintaining a healthy turfgrass sward can be a difficult balance to manage. A common approach to gaining putting speed is to lower the mowing height. Unfortunately, lowering the mowing height increases turfgrass stress (Young et al., 2015).

Bentgrass and Poa annua are less active physiologically during the summer months as a natural means to survive the stresses of summer. A low mowing height limits photosynthesis by significantly reducing the total leaf area of the plant. Raise mowing heights during stressful periods to maximize photosynthetic potential, increasing turf stress tolerance. While adjusting mowers to a taller mowing height, go ahead and switch out your rollers to solid instead of grooved rollers. This too will impart less stress on turfgrass plants.

4. Maintain Potassium Fertility

Potassium has been shown to increase the stress tolerance of turfgrass when maintained in leaf tissue at sufficient levels. Further, potassium is frequently deficient in soil tests. Spring core aeration is an excellent opportunity to amend soil macronutrients for the coming season. Consider an application of POLYON® 0-0-50 Micro at 2-4 lbs. K₂O per 1,000 square feet to open core aerification holes during the final spring aerification before summer for cool-season turf or the first aerification of the season for warm-season turf. Potassium will be released in a controlled manner for 16-20 weeks following Polyon 0-0-50 application.

5. Help Your Roots Breathe

Various issues related to summer stress are compounded by low soil air-filled porosity and poor atmosphere: soil gas exchange. The frequent use of quad tines or needle tines during stressful summer months will aid in enhancing gas exchange and increasing soil air-filled porosity. Ideally, small solid tines should be utilized on a biweekly basis, and the aerification holes left open to promote gas exchange. A simple rolling of the greens with a lightweight roller immediately following needle-tine aerification will close the holes enough to limit effects on putting quality. 

This is also a suitable time to supplement potassium while these small aerification holes are open. Apply POLYON® 0-0-50 Micro as a broadcast surface application at 1 pound of K₂O per 1,000 square feet (2 pounds of product) and simply turn the irrigation heads on for a couple of spins and POLYON 0-0-50 will disappear into the aerification holes.

6. Utilize Wetting Agents

Many greenkeepers overwater greens to keep them alive. This approach often creates more challenges as soil air-filled porosity reduces and heat retention increases. Further, challenges associated with excessive water in the top few inches of the profile may compound with excessive thatch, topdressing layers, or soil compaction.

The use of Fleet® 100 has proven effective in distributing water evenly through the soil profile. This is important in managing air-filled porosity and moderating soil temperatures. Fleet, when applied and watered-in sufficiently moves the wetting agent into the profile and enhances consistent water distribution throughout the wetted root zone.

7. Apply Title Phyte Systemic Fungicide

Harrell's ProtectMAX® Title Phyte® Systemic Fungicide is not only a quality potassium source; it also aids in the fight against turf stress and disease. University research has demonstrated the effectiveness of Title Phyte in mitigating turf stress, enhancing turfgrass quality, and suppressing pythium outbreaks. Title Phyte should be applied as part of a regular foliar fertility program throughout the growing season.

8. Apply Preventative Fungicides

Preventative fungicide applications are essential to maintaining high-quality playing surfaces throughout the summer months. Product selection and application timing are critical to ensure program success while keeping in mind the key factors that influence this. Site history, current weather patterns, disease pressure, and turf type are a few considerations for proper fungicide selection and application timing.

Many fungicide formulations provide plant health benefits beyond disease control. Syngenta's Action, Bayer's Stressgard®, and BASF's Intrinsic® line of fungicides are all examples of formulations that provide plant health benefits in addition to disease control. We recommend these fungicides as a key component of your summer fungicide rotation.

9. Air Movement

Air movement is critical to the evaporative cooling process. Without air movement, during the heat of summer, a high-humidity boundary layer is created immediately surrounding turfgrass leaves. As excessive heat accumulates and transpiration and evaporative cooling slows, photosynthetic efficiency can be dramatically reduced as the photosynthetic system begins to shut down.

Consider how vegetation or other obstructions adjacent to putting greens may negatively impact air movement. In some scenarios, it is beneficial to utilize a portable fan to encourage air movement or install a permanent fan in areas with chronic air movement limitations.

10. Consult your Harrell’s Rep

Your local Harrell's Representative is a wealth of knowledge who is always available to you as a resource. Each day Harrell’s Reps collectively visits hundreds of golf courses across the country. With these visits, Reps hear what other superintendents are seeing out there, what strategies are successful, and serve as a friendly ear during stressful times. If you find your turf up against a new challenge this season, a solution is likely just a phone call away.

References:

Dant, LA, SB Martin, LB McCarty, JP Kerns. 2020. Nitrogen source impacts Rhizoctonia leaf and sheath spot severity in ultradwarf bermudagrass. International Turfgrass Society Research Journal.

Hempfling, JW; BB Clarke, JA Murphy. 2014. Nitrogen Fertility, Mowing Height, and Topdressing Effects on Anthracnose of Annual Bluegrass. Proc of the Twenty-Third Annual Rutgers Turfgrass Symposium. Pp. 37-38.

Schmidt, RE; EH Ervin, X Zhang. 2003. Questions and answers about biostimulants. Golf Course Management. June pp. 87-99.

Young, J, M Richadson, D Karcher. 2015. Creeping bentgrass putting green response to combined mowing, rolling, and foot traffic under environmental stress. Agron. J. 107:6:1959-1966.