It’s a gross understatement to say that trees are great. They provide many benefits to property owners and society at large. Living in a world without winter color, wildlife enhancement, songbird habitat, framing, creation of a sense of place and space, a variety of textures and, perhaps best of all, shade would be a very different experience.

As tree care providers, your job is to keep existing trees healthy and to help property owners select good replacement specimens that will provide benefits for future generations. When it comes to insect pests such as borers that threaten the health of hardwoods, the best way to do so is through inspection, proper placement, separating trees from turf, creating good growing conditions and effective treatments.

Why? With the exception of the emerald ash borer, borers are attracted to stressed trees. So, reduce the stress, reduce the borer population. Good tree care means controlling borers once they infest your customers’ trees and working with other green industry professionals to help prevent them in the first place.

Separation of turf and ornamentals is always a good practice, helping to provide beneficial growing conditions for each. Photo: John Fech

Prevent borers via separation

Landscape designers stress the importance of separating trees from turf. This is not only a functional benefit. By doing so, the technique of mass/void is implemented into the landscape, where trees, shrubs and perennials are highlighted and made to be more impactful when cast against the void of turfgrass or other monochromatic or mono-textural elements.

Still, the functional benefits are many and should not be overlooked. Mowing efficiency and irrigation efficiency are the first two — keeping each on its own turf so to speak. In terms of the time and effort required to mow a lawn, solid blocks of turf present a much more efficient element in the landscape than ones filled with trees that slow the operator down by requiring them to circle or mow at angles to accomplish the goal.

Separation of trees and turf also provides large efficiencies in terms of irrigation. As with mowing, large, solid blocks of turf are much easier to irrigate than ones with trees, light poles or shrubs in them. As the heads cover the grassed area, the capacity to cover without distorting the spray pattern is preferable. Also, since most hardwoods require about a third of the water turf does, removing them prevents overwatering, resulting in less overall stress on the trees.

Prevention of damage to the bark and sapwood is another important benefit. By separating the turf from the tree, the need for close trimming of the turf with string trimmers and mowers is eliminated. Often relegated to 16-year-old boys that just want to get it over with, mowing is one of the most destructive and stressful operations for trees that exist.

Placement — size does matter

Adequate space for rooting is a big factor in creating good growing conditions for trees. Many other articles in this publication have imparted the knowledge that the root systems of trees extend for distances far beyond the drip line. It is your duty as a tree service provider to inform your clients of this fact and to help them understand that the activities that take place far away from the tree trunk can have a stressful influence on the trees in their landscape.

In most scenarios your input into the placement of new trees in the landscape will most likely occur soon after you remove one that has died. Clients usually want to replace the removed tree as soon as possible, which allows the opportunity to analyze the site and make recommendations based on the function of the new tree, the space available is a classic right plant, right place consideration.

Naturally, each situation is different. If the removed tree is the only one in the backyard, then almost unlimited options exist. If, on the other hand, the existing landscape was designed by a zealous plant lover that insisted on cramming dozens of woody plants into a relatively small property, the removal will leave a space that is best suited for a small to medium-sized crabapple or Japanese tree lilac rather than a sycamore or red oak.

Adult emerald ash borer. Photo: David Cappaert, Michigan State University, Bugwood.org

Regular inspection

As part of responsible tree care, regular inspections are essential. If your approach is to simply spray for borers on a predetermined schedule and send the client a bill, you’re doing a great disservice to the client, as well as your company. This protocol is problematic in that it applies product to trees that don’t need it, the arboricultural equivalent of fraud, and overlooks the ones that are already infested. Instead, begin a program of regular inspections. Charge the client for your time and effort to identify the signs and symptoms of borer invasion instead of how much volume of an insecticide that can be pumped on a tree. Inspections should note stressful conditions (such as soil compaction, trenching or overwatering) that often lead to the infestation of borers in a landscape. This routine will prevent damage and provide quality service to the customer.

Treatment methods

In addition to the prevention techniques listed earlier, direct treatments are sometimes called for. Each method has advantages and disadvantages. Trunk injection has become a popular method in recent years. Rob Gorden, director of urban forestry and business development with Arborjet, says, “Tree trunk injection treatments offer many advantages. They are environmentally friendly since they are sealed inside a tree. Nothing goes into the surrounding air, soil or water. They can be performed during nearly any type of weather on any size tree. They work quickly and, depending on the treatment, can last a season or act as a quick knockdown product.” On the other hand, injection is an invasive technique – a small amount of damage occurs when a hole is drilled or a needle-like apparatus enters the bark. Holes in bark can lead to pathogen invasion and decay. This approach can be effective for borers already in the tree, but feeding by borers may have destroyed the conductive vessels, limiting product uptake.

Emerald ash borer Photo: David Cappaert, Michigan State University, Bugwood.org

Before the advent of injections, trunk sprays were the main method used to control borers. It remains viable today. On the plus side, liquid applications of a residual insecticide applied to the lower 15 feet of the trunk bark offers good borer control without injury to the tree. Of course, timing for trunk sprays is crucial. They must be applied before the eggs hatch and borers enter the tree. Additionally, close attention must be paid to the length of residual for these products so the tree is not left unprotected during extended or multiple egg-laying periods. Also, any time a product becomes airborne, the potential for movement to nontarget species or landscape elements exists.

Soil treatments offer a third method for borer control. The plus side of soil treatment is that it doesn’t injure the tree. In addition, because these products should be watered in for maximum effectiveness, application on days when light rain is falling is still permissible. Unfortunately, soil treatments are not a good fit for properties with a slope because there is a greater tendency for runoff as well as uneven infiltration. Also, slower uptake is likely when the rootzone is compacted or limited in size, such as in a tree pit, or compromised in some other way by the presence of concrete.