Pest control is a category of much attention in the golf course maintenance budget and labor schedule. Regardless of whether it’s pathogens, weeds, nematodes or insects, all capture superintendents’ interest and demand expertise in diagnostic ability.
The degree of difficulty can be high when dealing with individual pests, beginning with determination of the causal agent, establishing a threshold for damage, researching the best timing for application of products for control and selection of effective products.
All plants on the golf course have pests. In addition to turfgrass, there are trees, shrubs, perennials, groundcovers, annuals and vines that are susceptible to infestation, and they must be monitored in both the dormant and actively growing seasons. In a general sense, the strategies that are foundational for turf also serve well for woody and herbaceous plant materials.
Preventive, curative methods
Just as with turfgrass pest control, preventive and curative approaches should be utilized. Preventive actions are best used when a known pest has been documented in the previous season, and an intervening strategy (pesticide application, pruning, mulching, fertilization, aeration, etc.) can be employed to break the life cycle of the biotic pest or boost the overall health of the tree. In many cases, a single or just a few treatments can go a long way toward keeping a tree in the category of an asset rather than a liability.
When an odd symptom is observed for the first time, it’s wise to compare that to what is seen and what the tree is supposed to look like. Abnormal growth is not always an actual pest; it just may appear to be one. For example, peeling bark or falling needles may be normal for the tree in question. As such, it’s helpful to get to know each specimen in order to be able to distinguish normal from abnormal.
Curative approaches are effective in situations where immediate action can have a positive influence in the short term, causing the responsible agent to cease or reduce its negative effects. Examples of effective curative actions include insecticide application for control of soft-bodied leaf feeders and removal of stems heavily infested with scale insects. In some cases, the curative should be considered as a one-shot action; in others, it should eventually dovetail with future preventive applications/actions.
It pays to scout
Curative and preventive approaches are much more effective if they are utilized as part of an overall plant heath care or tree pest control program. As with other pests on the golf course, such as anthracnose, yellow nutsedge or sod webworms, historical documentation and present-day scouting are crucial to long-term control. The documentation part is rather straightforward; it can be as simple as a notebook (or electronic form thereof) with a listing of each hole, set of tees, etc., with monthly notes about observed pest infestations and the action taken – either none, monitoring or the form of curative action employed.
In one way or another, regular tree inspection needs to occur in order to be proactive and effective. It may make sense to categorize the course in terms of priority areas, such as donor or high-value stakeholder locations. Another high-priority category could be the areas on the course with high target value, such as spots under trees with items of great importance, such as where people congregate. Practice greens, tees with nearby trees and refreshment stands can fall into this group. Weak, young or aged trees often make up a third category. If they serve a valuable function and are worthy of being retained on the course, these trees should be inspected as a group, as their needs are often higher.
Regardless of whether it’s hole by hole or by priority area, inspection requires labor and talent to get the job done properly. Simply put, scouting requires an outlay of cash and a line item in the golf maintenance budget.
Generally, there are two ways to pay for scouting:
1. Hire and train in-house golf course employees to perform the job on a regular basis.
2. Subcontract with a reputable tree care service to routinely inspect trees in each of the categories.
Tree by tree
Many tree species have known maladies, both abiotic and biotic, as part of the overall regional ecosystem. In fact, (though it’s not recommended) some beginning arborists, pathologists and entomologists learn tree identification through spotting certain pests and then learn to recognize the specific tree that is associated with them. Examples of certain closely associated pests include:
Crabapple – apple scab, cedar apple rust, fireblight.
Elm – Dutch elm disease, elm leaf beetle, elm bark beetle.
Hawthorn – leaf miner, aphids.
Pin oak – chlorosis, gooseberry leaf gall.
Hackberry – nipple gall, lacebug.
Sycamore – anthracnose, lacebug.
Linden – leaf miner, Japanese beetle, lacebug.
Cottonwood and poplar – petiole leaf gall, cytospora canker.
Ash – emerald ash borer, ash flower gall mite, ganoderma root rot.
Norway, red and sugar maple – sunscald canker, susceptibility to mower blight, tar spot, verticillium wilt, leaf scorch.
White oak – oak wilt, armillaria root rot.
Long-needled pine – pine needle scale, pine tip moth, dothistroma needle blight, sphaeropsis tip blight, lophidermium stem blight.
Black tupelo – forest tent caterpillar.
Arborvitae – root rot, twig blights, Berckmann’s blight, aphids, spider mites.
Blue spruce – spider mites, valsa canker, leucostoma canker, rhizosphaera needlecast.
Pest by pest
Half of the following are biotic pests and the others are abiotic, which are caused by nonliving organisms but still considered pests. It’s most helpful to think of them as maladies, rather than jumping to the conclusion that the symptoms are indicative of an insect, mite pathogen.
Foliar insects – Damage commonly appears as round, serpentine or blob-like holes in leaves; sometimes as speckled or peppered as if stuck with pinpricks. A simple 10x hand lens helps to see small objects on a leaf or needle.
Foliar diseases – Many plant diseases have a pattern. Distinct ovals and round spots often are symptoms of leaf disease. Others may quickly kill a stem, which are usually referred to as a blight.
Borers – Holes in the trunk and lower limbs are the most obvious symptoms of borers. Many holes, lots of sawdust-like frass and leafless stems, are serious symptoms.
Stem-girdling roots – Sometimes visible, sometimes not, wayward roots grow around the trunk instead of outward from it. As girdling roots expand in diameter, they impinge on the trunk tissue and other roots, causing a restriction of the rate of movement of water and nutrients within the tree.
Vascular wilts – Pathogens clog the water-conducting vessels and plant wilting results. Many of the vascular wilts, such as verticillium, are soil-borne and invade through a tree’s root system.
Herbicide drift – Distortions of young stems and leaves, often observed as curling, cupping, thickening, pronounced veins and twisting, are symptoms of herbicide drift.
Soil compaction – Compressed soil particles exclude soil oxygen and decrease lateral and vertical movement of roots. Soil issues are manifested by limited root growth (easily seen in turf) and reduced branch growth (seen on trees and shrubs).
The rule is: right tree, right place. All plants have preferences about the conditions they grow in: sun, shade, moisture, wind, soil type and surrounding plant compatibility.
Review, Repair, Replace
Curative pest control can be thought of as repairing a tree. Overall, the chronology of tree pest control for the golf course goes like this:
1. Scouting observations
2. Identify the malady or causal agent.
3. Review and evaluate the severity and extent of the malady.
4. Consider the possibility of treatment in terms of timing, importance of the tree in the golfscape, existing condition and health of the tree and cost of treatment options.
5. Appropriate treatment or replacement
6. Evaluation of effectiveness later in the growing season
In some cases, repair is best; in others replacement is the appropriate choice. Generally, if a tree exhibits a classic symptom for the species early in the tree’s life, replacement is the better option, as it likely will return again and again as a malady to be dealt with. Of course, each situation, malady, disease, insect and golf course, are different and consideration of each should be made on a tree-by-tree basis.