Is it easier to push a boulder up a hill or down a hill? That was the seminal question posed to me by one of our colleagues a few years back. Other than the issue of heavy rock management, what was he getting at?
Actually, his question could apply to many things in life – car repair, credit troubles and time management – but in this case he was referring to preventing turf diseases. The key message here is that pathogens and abiotic conditions are almost always easier to prevent than to cure. Plus, a bonus that comes along with implementing preventive techniques is that the turf just looks better than when one relies on curative methods alone.
Considering that we are focusing on prevention and looking ahead, the future begins with the past for turf diseases. Because many turf diseases tend to repeat themselves in the same or adjacent locations, it’s helpful to look back at notes made in previous growing seasons.
Notations about where and when infections occurred can be very helpful in managing pathogens in upcoming years. Regardless whether it’s electronic or pen and paper, records are foundational to disease prevention. In many instances, occurrence will relate to a specific weather condition that should also be noted.
Digging deeply into the historical accounts, it’s helpful to do so in a variety of ways. In addition to reading the notes such as “Pythium root dysfunction infection on No. 3 tee and No. 7 approach,” other helpful information can be gleaned by checking through records of fungicide applications and asking for recall from other workers at staff meetings.
Read more: Taming turf disease
Historically, weather records can also be viewed to learn about the timing related to temperatures, etc. However, usage of exact calendar dates should be avoided as weather patterns can vary widely from year to year. Regardless of the method, bringing incomplete records up to date and filling in the gaps where necessary is a good place to start.
Seeing and inspecting
With thorough records in place, it’s time to fast forward to the current. In order to perpetuate diseases, it’s important to recall that a significant part of the well- established trifold equation, aka the disease triangle, is the pathogen itself. For many root and shoot diseases, simply knowing where the diseases have been and are likely to be again is key to controlling them – thus the need for monitoring and record keeping.
Monitoring, sometimes called scouting, can be accomplished in several ways, but the common action(s) are seeing, observing, inspecting and correctly identifying the problem. One way is focused and intentional, where certain staff members set off to a specific area of the course where records have indicated previous infections and surveying the current conditions.
Read more: Battling bermuda disease
Another is adding another dimension to the necessary tasks of the day, such as changing cups and moving tee markers. Each method, and even a hybrid of the two, has its place; no matter which is chosen, our recommendation is to implement which is the best fit for the unique features of the course. As turf in various locations is inspected, it’s important that descriptions and observations be entered into current year records.
The second part of the disease triangle is the susceptible level of the host. Certain turfgrass species are known for their tendency to become infected with particular diseases. Within those species, specific cultivars have been documented to be more likely to become infected under the same growing conditions than others. For example, Kentucky bluegrass has historically been linked with variable susceptibility to Bipolaris/Helminthosporium leaf spot.
Depending on which trial you are looking at, it’s likely that about a third to a half of the cultivars will be very susceptible, a third or so somewhat resistant and a third highly resistant to infection from the fungus.
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The phenomenon of genetic resistance of the species and cultivar harkens back directly to the previously mentioned anecdote of pushing a boulder up a hill. Ignoring the inherent susceptibility can certainly be done, but why? Wouldn’t you rather push it down the hill? Good sources of disease resistance information include the National Turfgrass Evaluation Program (NTEP) trials, land grant universities, on-course demonstrations and seed producer fact sheets.
The third part of the disease triangle – suitable environmental conditions – is one that can sometimes be controlled and sometimes not. Often, the contour and surroundings of a golf course lead to the onset or the delay of pathogen development. Most fungal and bacterial species are favored by humid and/or moist environments. Golf course architecture and layout often lead to reduced airflow and therefore disease development.
Two actions that can be taken to prevent or at least reduce infection are the installation of fans to move air over the turf surface, and tree removal or pruning to allow greater sunlight penetration and air movement. In many situations, some golfers and green committee members may object to the presence of fans. As well, many stakeholders like to see and enjoy shade from trees while they play.
Removal can certainly reduce stagnant air and increase sunlight to the turf surface, greatly improving turf-growing conditions. But like many other actions one could take, change often brings along negative consequences. Judicious implementation of both may be the best approach.
Aeration: a routine method
Especially with root diseases, good drainage and air penetration into the turfgrass root zone is essential to encouraging vigorous growth and discouraging the development of pathogens. As such, deep-solid tine, hollow core and other methods of aeration have become routine.
As with other actions on the course, such as pruning cane-growing deciduous shrubs like lilac, dogwood and viburnum, an initial reduction in appearance and function occurs. However, the long-term benefits of improved rooting, water penetration, oxygen penetration and disturbing of soil layers usually results, thereby justifying the procedure.
Read more: Aeration essentials
From a prevention standpoint, consideration of historical records, course conditions, weather patterns, thickness of thatch, future planned events and species tendencies are good considerations for the frequency and extent of aeration methods.
For most diseases, (powdery mildew is an exception) abundant moisture is required for infection to occur. Unfortunately, vigorous turf growth also depends on abundant (or at least not lacking) moisture. As such, there is always a balance between keeping the turf too moist or too dry.
To a certain extent, the desired irrigation frequency and amount is a function, or at least should be, related to the other conditions on the golf course.
For example, if one is struggling with heavy clay fairways, applied water will tend to be retained. If frequent deep soakings are applied, the voids between soil particles are likely to fill with water and be retained for many days beyond favorable, leading to the demise of the root system and encouragement of subsurface pathogens. When irrigation is applied, morning is the preferred timing to reduce dew layers and dry the turf more rapidly.
A final aspect of disease prevention is the prudent application of fungicides. Again, back to the boulder narrative: Preventive fungicides tend to be more effective than curative ones.
One central reason is that preventive products are applied to healthy plants, while curative agents are applied to turfgrass with weakened roots and shoots. In addition, the volume of inoculum or disease propagules is much greater once the disease has started development to any extent. In the previous example of leaf spot, curative fungicides can be applied. However, at that point they will be sprayed on turf plants with weakened stems, senescing non-photosynthetic leaves and struggling roots.
Read more: Talking fungicides
For these products, the aim is to arrest the disease long enough for the turf stand to regain health and vigor and re-establish healthy plant parts. Both curative and preventive products offer benefits for disease management.
All in all, preventing turf diseases on the golf course is a complicated and multifactor endeavor. The factors of recordkeeping, monitoring, species/cultivar selection, airflow modification, aeration, irrigation management and judicious usage of fungicides all play a key role in success.