Playing surfaces where direct sunlight and air movement are limited are more likely to experience turf health issues when hot and humid weather conditions are experienced. Similar to a drainage plan, every golf course with more than a few trees should have a tree management plan where turf health and playability are prioritized. Tree removal can be an emotional topic and it is important to establish with stakeholders early on that a golf course is being maintained, not an arboretum. Fans have proven successful at improving air movement and they are beneficial in almost all climates when putting greens are located in pocketed environments.

Another key part of summer success is recognizing and accepting the fact that some areas need to be treated differently when the weather gets tough. There will always be parts of the course that struggle earlier or more often than others. Sometimes the reason is clear, sometimes it isn’t. Regardless, using the same agronomic program there as you do in stronger areas is a recipe for trouble. Maintaining more-vulnerable playing surfaces differently to protect turf health during stressful periods is essential. For example, some greens may need to be rolled less often, or mowed at a slightly higher height of cut, or mowed with different rollers on the mower to minimize mechanical stress and give turf that is prone to struggling the best chance of survival.

Adjusting Application Schedules

When the weather does not cooperate, adjusting the timing of plant protectant applications is necessary. High temperatures and humidity will increase disease pressure, so shortening the interval between fungicide applications is recommended to ensure outbreaks do not occur. If there is excessive rainfall, the schedule will need to be adjusted based on access to the course. For example, if the forecast is unfavorable on a planned application day, applying the plant protectants ahead of schedule to ensure disease coverage is in place produces better results than waiting until the weather improves to make the application.

Consideration must also be given to how different FRAC codes are rotated. DMI fungicides can have a growth regulating effect and issues can develop if these products are applied during higher temperatures. Using products that will not have growth regulating effects during the hottest stretches of the summer will benefit turf health while preventing disease outbreaks.

Excessive rainfall in the spring and early summer will cause the barrier created by preemergence herbicides to break down sooner than expected, resulting in weed encroachment later in the summer, especially in areas where turf is thinning. This is a scenario we have seen several times in recent years, specifically with crabgrass and goosegrass breakthrough. Split applications of preemergence herbicides can help extend control, but regardless of the preemergence program, scouting throughout the summer is important for determining when and if postemergence applications need to be made. It’s always better to get ahead of any breakthrough before playability and course appearance are significantly impacted.

Nitrogen applications also have to be adjusted to avoid issues during hot summer weather. High temperatures stimulate microbial activity in the soil, causing organic matter to break down faster and release more nitrogen than when temperatures are cooler. Research conducted at the University of Tennessee found that, in a controlled environment, as much as 1 pound of nitrogen per 1,000 square feet can be released from organic matter breaking down when soil temperatures were 77 degrees or higher over an eight-week period. The amount of nitrogen released is influenced by the amount of organic matter present in the rootzone.

Continuing to apply nitrogen when temperatures are high will only stimulate excessive growth, impacting both turf health and playing conditions as well as contributing to organic matter accumulation. Disease issues, having to mow more frequently, an increased risk of scalping and slower green speeds later in the day can all result from applying too much nitrogen. Reducing or suspending nitrogen applications when temperatures are high has proven successful at many golf courses. It is also important to consider the nitrogen source. Products with water-soluble nitrogen will release much faster than slow-release forms of nitrogen, resulting in rapid growth.

When temperatures are higher, plant growth regulators (PGRs) are metabolized more quickly by the turf. As a result, regulation will not last as long as it does when temperatures are mild. Using a growing degree-day (GDD) calculator and monitoring clipping volume can help determine when PGR applications are necessary to maintain consistent growth during the summer months.

Modifying the Mowing Schedule

Tough summer weather also requires making adjustments to the mowing program to protect turf health and avoid self-inflicted damage from mechanical injury. Heavy summer rains limit access to the course and mowing before or after rain events when the course is dry enough is recommended. Depending on the forecast, making this adjustment could mean scheduling extra staff to mow more of the course before a storm, mowing later in the day during a break in the weather, or scheduling extra staff on the weekend to mow more of the golf course than usual. If the putting greens are typically walk mowed, switching to a triplex for a period of time can free up some staff for mowing other areas if you need to get ahead or catch up.

Prolonged high temperatures and minimal rainfall necessitate reduced mowing so unnecessary mechanical stress is not placed on turf that is hardly growing or in drought-induced dormancy. Superintendents should be especially careful about wear and tear in areas that are not irrigated or have limited coverage. Adjustments could include only mowing portions of the rough that need it, or mowing fairways one less time each week until more-favorable weather conditions return. It may even be necessary to forgo mowing in the afternoons so additional stress is not placed on the turf during the hottest part of the day. Increasing hand watering is a sound option for reallocating labor if mowing frequency is reduced during hot and dry weather. In extreme situations, it may be necessary to restrict or limit carts to reduce traffic on dormant turf during dry weather. While golfers might not be happy about this decision, it is a discussion worth having when the forecast indicates that prolonged hot and dry conditions are on the horizon.

Fairway and putting green edges, and putting green collars, need to be monitored closely as stressful weather persists because these areas are extremely prone to turf issues. Using a mower with a solid roller and/or set at a slightly higher height for cleanup passes can help. Using turning boards for walk mowers and changing where the roller starts and stops are all strategies that can be used to protect putting green edges. The beginnings of fairways and curves near bunkers also tend to be among the first areas to show signs of wear during summer. These areas still need to be mowed, but having the operators lift and drive around them once a week can reduce the amount of stress. Additionally, cart traffic should be directed away from these areas as much as possible, especially if they start thinning.

Autonomous mowers have proven beneficial during a variety of adverse weather conditions. The light footprint of these mowers makes it possible for mowing to continue when the ground is soft. Because they are lighter than traditional rough mowers, less stress is placed on the turf, which also keeps grass healthier heading into a hot and dry stretch.

Data Collection

Data collection provides an objective way to evaluate how different playing surfaces are performing and how adjustments to the maintenance program impact playability. This is especially valuable for managing putting greens during the summer months because you don’t want to perform any practices that are not necessary. If you are not yet collecting data, measuring clipping volume is a good place to start because it provides insight into the impact of fertilizer, PGR applications and weather conditions on growth. When clipping volume is compared to putting green speed, trends can be observed that may indicate opportunities to mow or roll less frequently during difficult weather while still providing the desired playability.

The USGA GS3^™ ball takes measuring putting green performance metrics to the next level by making it possible to quantify smoothness, trueness and firmness in addition to speed. Trends can then be monitored and used to evaluate surface management practices to optimize turf health while delivering the desired conditions.

For water management, the data from moisture meters is extremely valuable to help guide irrigation decisions. While these tools are most commonly used on putting greens, they can also be used to map soil moisture in fairways to accurately locate wet and dry areas that may be prone to turf loss during extreme summer weather. Another way data can be used to guide irrigation decisions is with ET-based irrigation scheduling. “Feel” will always be part of water management during tough weather, but data adds objectivity to your intuition that will help you make effective site-specific adjustments to irrigation.

In addition to improving decision-making, data collection can help you communicate more effectively with golfers and stakeholders. This is critical during summer when playing defense can have a temporary impact on playing conditions. Establishing ranges for metrics like green speed and firmness and tracking results over time makes it possible to educate golfers about how putting greens are being managed to meet expectations while adapting to the weather. This is by no means a recommendation to post green speeds by the first tee, but there is great value in being able to talk with golfers and decision-makers about measured putting green performance rather than perception. Collecting data throughout the year will also help you explain the impact of defensive maintenance practices on playability. You can show how temperatures in the high 90s prompted reduced mowing and a slight decrease in green speed, only for speeds to return to normal a week later when the weather cooled. Instead of having a golfer’s perception of playing conditions based on one day, this information helps them see the full process unfold. 

Summary

Every golf season produces a unique set of challenges that must be navigated, but you can rest assured that summer is going to have some tough stretches almost every year. Being prepared to adjust when the difficult times come can be the difference between success and serious problems. Turf health, past experience and the weather forecast all need to be evaluated as changes are considered. Sacrificing some playability in the short term may lead to golfer frustration, but repairing dead areas will have a much longer impact on playing conditions. Do not underestimate the value of communicating with golfers and stakeholders about why adjustments are being made throughout the summer, especially if you can bring some hard data to the conversation. Every summer will have its struggles, but investing in a strong agronomic foundation and being prepared to adapt daily management on a site-specific basis will help keep your grass healthy and your golfers happy.