Managing tree maladies

Successfully treating biotic problems that target trees requires commitment and understanding of the ailments.


Filed to: Trees, Disease

Aerial view of Ghost Creek golf course
Caring for trees on a golf course requires a basic understanding of the diseases, pests and other ailments that target them. Adobe Stock photo

Tree insects, diseases and abiotic influences are sometimes baffling. They often leave us wondering what to do and when to do it. When it comes to biotic maladies — those caused by living organisms — a superintendent often has a little more control or at least a few more intervention options than those of the abiotic variety. The strategies involved are best utilized in a systematic approach, which leads to a significant reduction in damage to woody plants on the golf course.

Abiotic influences are often imparted by various “unchangeable” influences, such as sun reflection from the clubhouse windows, radiated heat from the patio, super-hot summer weather, strong winter winds, lack of natural rainfall, etc. Sure, some abiotic causal agents are within the superintendent’s control, such as making sure that seasonal hires use string trimmers correctly and installing white PVC collars in winter to prevent sunscald and critter damage to thin-barked species, but most are difficult to influence. 

Though still hard to control, the damage from most biotic maladies can be lessened, at least to some degree, by the people who care for the trees. How so, and what are the methods? They are many and varied, and the more of them that are utilized, the better the efficacy.

Aerial view of Ghost Creek golf course
Root damage often leads to decay and a cessation in uptake of water and nutrients. Photos by John Fech, James Kalisch and Tracy Bahle

Scout and monitor

The bottom line of looking for tree pests and maladies: Do it often, and don’t skip a week. Finding and treating insects is much, much easier when they are small than when they have reached full size or when they have shifted from their damaging life stage (either larval or adult) to their resting or overwintering stage. 

Bagworms and scales are good examples. They are relatively easy to control when first detected in the early larval stages, but next to impossible to manage once they have reached maturity or even half maturity. Monitoring also tells you if the preventive strategies you have implemented, such as cultural control methods and sanitation, have been effective. 

Early detection is also crucial for managing tree and shrub pathogens. For example, noticing when the spores of cedar apple rust are beginning to disperse from their fruiting bodies is helpful in fine-tuning the application of fungicides for crab apples on the course. For insects and biotic diseases, making thorough notes regarding dates, life stages and growing degree days helps to perfect control programs in following years. Early detection applies to nonpest biotic issues, such as the development of co-dominant leaders. If one is removed early in the tree’s life, recovery almost always occurs within a few years and prevents major restrictions on water and nutrient flow later in the tree’s life, just when it’s starting to become an asset.

Aerial view of Ghost Creek golf course
Essential tree anchorage is also often compromised by root damage.

Unfortunately, when implementing scouting, it can be an easy thing to send to the bottom of the “to-do” list. It can feel less productive than performing many of the other pressing tasks involved in the care of a golf course; sometimes you may not find anything while scouting, and it can feel like a waste of time. Building a dedicated monitoring program, though, will benefit you and your team in the long run. To help make sure scouting sticks, make it a dedicated part of select team members’ duties. Not only will this create pressure to perform the task, but it makes the monitoring more effective by cutting down on variability. If the same folks are doing it — and doing it well — you can trust the data they collect to be accurate.

Regarding the actual scheduling and implementation of scouting, since each course is different in terms of budget and available staff, it helps to be flexible. It may be that it’s best to assign a couple of crew members to scout as a part of their full-time job, or at least make it their highest priority as they go about their workday. Another approach is to ask each worker to be on the lookout for biotic pests as a part of their overall assignments and report their observations daily. Either way, the key is to be committed to scouting and consistently make observations.

Aerial view of Ghost Creek golf course
Decay or other biotic damage to trunks limits essential water and nutrient conductivity. Unfortunately, there is no control for these issues, underscoring the need for routine monitoring.

Identify the beast

Once you have captured or discovered something during your scouting efforts, the next necessary step will be accurate identification. There are dozens of insects that feed on trees and shrubs planted on golf courses, as well as quite a few pathogens that are infectious with the capacity to cause short- and long-term injury. 

Fortunately, there are good references for identification, in print and electronic form. Two of the all-time standards for print references are “Diseases of Trees and Shrubs” and “Insects that Feed on Trees and Shrubs,” both written by Wayne Sinclair, Warren Johnson and Howard Lyon. Another stalwart is “Garden Pests of North America” by Whitney Johnson. A few online sources of information to consult are the “Guide to Insect Pests of Woody Plants” from the University of Kentucky (, and, a site designed to assist in the identification of plants and animals while also generating data for science and conservation.

Every golf course maintenance operation should be familiar with at least a couple of these references so they can be utilized with no hurdle to access. Other sources of information on identification are local International Society of Arboriculture-certified arborists and land-grant university plant pathologists, entomologists, horticulturists and arborists. 

Aerial view of Ghost Creek golf course
Though they may look really threatening to tree health, infestations of the ash flower gall rarely result in long-term damage.

Setting priorities

When beginning a biotic scouting program, it can be daunting to imagine checking every woody plant for a problem. In truth, certain trees and plants in a golfscape are simply more important than others. A good question to ask yourself is, “Which trees are the most important in terms of return on investment?” In most cases, the location, species and tangible payoffs will help identify these. The key to success is to focus available budget dollars on these specimens.


The provision of shade, the screening of undesirable views and protection barriers between adjacent fairways are good examples of the tangible benefits associated directly with location. Others include backdrops for greens and identification of dogleg turns. When trees provide these specific benefits, they tend to rise to the top of the list for allocated resources.

Aerial view of Ghost Creek golf course
Many tree cultivars are naturally resistant to pests such as apple scab and fireblight, while others are quite susceptible.


Targets are items of high value, such as the clubhouse, golf cart storage, pro shop, maintenance facility, etc., as well as those of the highest value — your golfers and crew members. Whenever a tree is close to one of these, it’s important to consider its condition and how likely it is to cause injury or damage as a result of tree failure or branches falling. Regular inspection by an ISA-certified arborist and implementation of their recommendations will greatly reduce the potential for undesirable outcomes. In addition to regular scouting by staff members, routine consultation with a qualified professional is greatly beneficial as well.

Species names

Some species have historic, local or sentimental value. For example, the state tree of your state, the name of the course, a tree planted by a founding member of the club, and local notable or influential stakeholders are worthy of attention. After all, words mean things, and in this situation, the names of trees convey respect or a tip of the cap; these specimens usually deserve a little more attention than a run-of-the-mill elm or eucalyptus.

Aerial view of Ghost Creek golf course
A location on the course where people congregate helps to prioritize tree value. Photos by John Fech

Signature trees

In some cases, a golf course is known for a well-placed or signature tree. Architects and designers often specify trees and shrubs in certain areas to denote feelings or a sense of place. Signature trees usually are prioritized in the “of high importance group” as well.

Aerial view of Ghost Creek golf course
In some cases, the species name may help prioritize the attention paid to a certain tree, such as the state tree (in this case, a Kentucky coffee­tree), or when the course name includes a tree species, such as Sycamore Ridge.

Where to look

Generally, it’s best to focus on the permanent parts of the tree in terms of prioritization. In most situations, leaves, stems and even branches can regrow; however, the base, roots and trunk must be preserved in order for the tree to remain a healthy fixture on the golf course. In order of concern (and a few examples of biotic tree maladies that affect these parts of the tree):

  • Base/bole — for example, Armillaria root rot, roundheaded apple tree borer.
  • Roots — Ganoderma root rot, black vine weevils, root aphids.
  • Trunk — white rot, brown rot, turkey tail fungus, oyster mushrooms, hardwood borers.
  • Branches — Zimmerman pine moth, cytospora canker, valsa canker, armored scales.
  • Leaves/crown — Japanese beetles, spider mites, apple scab.
  • Flowers — ash flower gall, camellia petal blight.

In some cases, all or most parts of a tree are affected. When this is the case, when all the bad stuff hits the fan such as with oak wilt, anthracnose, Dutch elm disease and pine wilt, a “super pest” category is reached. 

And then there are cases of “mimics,” when maladies aren’t maladies at all — they’re malady look-a-likes. These are features that look a bit out of the ordinary, often causing a person to scratch their head and mumble to themselves, “Is that a bug or a fungus, or is it supposed to look that way?” Examples of these include exfoliating/peeling bark, two- or three-colored leaves, most conifer flowers and lots of browning inner foliage. The key to managing mimics is to become thoroughly familiar with them and spread the word that this is a natural part of the tree and not to worry about it.

Aerial view of Ghost Creek golf course
Extensive damage usually puts a tree in the “too much is too much” and “need to remove” category, especially if it’s in an area commonly frequented by golfers or crew members.

Confronting the issue

When seeking to manage pests and pathogens that are creating problems in golf course trees, there are many options for suppression and management. Chemical management strategies tend to be the option many turn to first, but despite their efficacy and ease of use, sometimes there are other options that can provide long-term suppression and reduce the need and budget for inputs. The time-tested strategies of scouting, identification, prioritization, consideration of the part of the plant that is damaged, and the concept of “right plant, right place” are key elements.

In some cases, natural or genetic resistance is available. Most often, the opportunity to utilize this method exists when planting or managing species of trees and shrubs with more than one cultivar, such as crab apple, rose, spruce, pine, hawthorn and poplar. For example, there are easily over 500 cultivars of crab apple on the market today. At least half of them are susceptible to apple scab, fireblight, cedar apple rust or combinations thereof. Being specific about the cultivars chosen and installed on the course can make a huge difference in terms of the need for future disease-control applications.

Finally, how much is too much? Through the process of identifying the malady, monitoring for its presence, prioritizing the tree’s importance, and scheduling and implementing various treatments, it’s important to determine when the negatives outweigh the positives and the removal of the problem tree is the best course of action. Navigating this process is tricky and requires knowledge, experience and patience. The salient elements of this consideration include original purpose, location, benefits, costs of management and political resistance to removal. Still, in some cases, tree removal is a best management practice that should be taken.

Aerial view of Ghost Creek golf course
Deterioration of the bole often indicates loss of function of the roots and trunk and is a tree part to inspect routinely.

John C. Fech is a horticulturist and Extension educator with the University of Nebraska-Lincoln. He is a frequent and award-winning contributor to GCM. Jonathan L. Larson is an assistant professor and Extension educator at the University of Kentucky in Lexington.

Filed to: Trees, Disease

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