Tree Care: A Shot in the Trunk

Trees don’t cough or sneeze. Their eyes don’t water and they never get fevers or complain of body aches. Even during the most chilling winters, trees don’t succumb to colds – but they can get sick.

As the spring season starts, many tree care workers who may have received flu shots in December are donning their own doctor gear in preparation for some large patients. Insects and diseases that attack trees as the weather warms are currently planning their takeovers, targeting weakened and sometime even healthy trees as they come out of dormancy.

But, as with several human ailments that can be treated or prevented with a quick shot in the arm, many trees also are candidates for curative and therapeutic injections by way of micro- and macroinjection. Though different from human vaccinations in many ways, injections are becoming popular treatments for arboreal ailments.

MICRO MANAGEMENT. If Dad’s allergic reaction to poison ivy left a rash on his arms and legs, would the rest of the family ask to be doused in cortisone along with him? Unlikely. Similarly, many tree care clients who request pesticide sprays to eliminate insect problems have neighbors who would rather not be exposed to the pesticides. Moreover, recent legislation is restricting pesticide spraying amid environmental concerns over spray drift and water quality.

"There’s a lot of concern now about the drift of products moving off target," comments Mike Ventura, president, Ventura’s Pest Control, Rancho Cucamonga, Calif. "With microinjection, it’s a closed system, so you know the material is going right where you need it, it’s safe for the environment, and from a workers’ compensation point of view, it practically eliminates the possibility of any material getting on the applicator."

Though the process differs slightly depending on the manufacturer, most microinjection applications call for drilling an 11/64-inch (less than ¼ inch) hole into a tree’s root flare – where the trunk widens at its base in transition to the root system – and inserting the nozzle of a plastic or metal unit filled with injection material into the hole. The tree’s vascular system then slowly pulls in the injected material. Other processes eliminate the need to drill by injecting a syringe-style applicator and depositing the chemical directly into the tree’s active xylem tissue.

"Drilling through the bark and only into the outer conductive tissue of the tree – the active xylem tissue – is what allows systemic fungicides and insecticides to work properly," explains Nate Dodds, president, J.J. Mauget, Arcadia, Calif. "Systemic means ‘becoming part of the system’ and the conductive tissue is the system that carries water and nutrients throughout the tree. By getting the material in there right away, the tree accepts the flow of product that’s being injected, just as it would accept water or nutrients."

Of course, the microinjection materials are stronger than water and nutrients, and are mainly aimed at killing or reducing insect and disease problems. Injections are popular for treating Dutch elm disease and other fungal pathogens like oak wilt, in addition to several insects. "Leaf-feeding insects, such as aphids and spider-mites, as well as piercing and sucking insects, like some caterpillar stages or leaf beetles, are controlled very well with injection," explains Roger Webb, president, Tree Tech Microinjection Systems, Morriston, Fla. "They’re mostly feeding on the succulent leaf tissue, which is really the end point of chemicals that are injected into trees, so they’re feeding right where the insecticide will end up."

Additionally, many tree care workers use injection when fighting boring insects that are not accessible through spray applications. "Boring insects are the most difficult to control because they’re working from underneath the bark," Dodds comments. "You cannot see their activity, and most pesticides won’t penetrate deep enough to control those insects. You need to use an insecticide that can become part of the tree’s living system where the insects are feeding."

But as "boring" as some pests may be, insects and fungi can damage trees quickly. For that reason, most fungicide applications should be made early in the season. "The optimal time to inject fungicides is in late summer," notes Chip Doolittle, president, ArborSystems, Omaha, Neb. "The injection should be made before leaf-out, so this late summer timing is perfect to allow the chemical to be taken up before the tree goes dormant and to keep it there through the spring."

Ventura also recommends making applications before leaf-out, but times his applications for early spring. "The benefit of injecting at the beginning of the growing season is you’ll have more time on your hands as the season gets going," he says. "In February and March, the trees are still dormant and you can get a lot of injection done before other maintenance services begin."

In terms of insecticides, Webb notes that many insect infestations can be treated curatively in mid-season or as they appear. "However, you have to get to borer infestations when they are relatively new because as the adults go through mating and egg-laying cycles and begin to breed, the problem becomes too magnified to be treated effectively," he says.

Efficacy is an important part of microinjection, which requires injecting small, concentrated amounts of material – usually no more than 3 milliliters in volume – at multiple points around the tree. To determine the number of injection points, most manufacturers recommend dividing the diameter of the tree at breast height in inches (DBH) by two and making that number of injections about 6 inches apart at the root flare. A tree with a DBH of 10 inches would require five injection points spaced evenly around the base of the tree.

Depending on the process, microinjection can take as little as a few seconds per injection to treat an entire tree. Ventura found this to be a selling point of the process. "We’re selling time, and the whole process only takes about 90 seconds," he comments. "It trims a lot off of our labor costs, and because you can make treatments in almost any weather, you don’t lose the time and productivity that you would when you’re scheduling spray applications around the weather or clients’ schedules."

To price microinjection, Ventura begins by using the DBH he measures for the initial treatment. "Pricing is based on the DBH of the tree, which tells you how many injection sites you need," he says, explaining that contractors must recover their costs for each unit of injection material. "For large projects with several trees we take the average cost to treat each tree and add our mark-up. For sites where we’re only treating one or two trees, we charge a flat rate."

Dodds mentions that most contractors charge between $3 and $10 per caliper inch for microinjection, depending on the number of trees treated, the type of chemical and what the market will bear. He also notes that a rule of thumb in the industry is to have a service charge of three to four times the chemical cost.

HOLY MACRO. If "microinjection" means quick flu shot-style applications, then "macroinjection" must equate to invasive surgery, right? Not exactly.

"Macroinjection – or macroinfusion as it is more frequently called – sounds like a big injection hole, but it’s really just a large amount of material that’s going into the tree," explains Tom Prosser, president, Rainbow Treecare, Minneapolis, Minn. "With a microinjector you’re usually putting in around 1/10 of an ounce of material per injection site, but with macroinfusion you may use 30 or 40 gallons of material for one tree."

Additionally, Prosser noted that macroinfusion is more often used for disease control than insect management, but alternative methods for pest control on trees should be examined before any injection treatments are used. "The first order of any practitioner is to do no harm," Prosser continues. "But there are reasons to use injection for very specific purposes. If you have a boring insect inside the tree, it may take 60 days for a soil application to get into the tree, but through trunk injections you can kill the pest at that moment. Also, Dutch elm disease and oak wilt are both internal vascular fungi and injection is one of the only methods now that has good results in terms of protecting the tree."

To treat Dutch elm, oak wilt and other diseases with macroinfusion, tree care workers use application techniques similar to microinjection. The process first involves drilling a 15/64-inch hole into the tree’s cambium layer where the active tissue resides, followed by inserting plastic "tees" attached to each other with heavy plastic tubing. Because macroinjection involves diluting chemicals in gallons of water rather than injecting concentrated material, many tree care workers using this method will mix the product with water in a large tank or trashcan. Using an electric or hand-powered pump at about 15 to 20 psi, the material is pushed from the tank, through the tubing and into the tees, which direct the chemical to the tree’s vascular flow.

According to Prosser, proper macroinjection should allow the tree to take up all the material in less than an hour. While this may sound far less productive than microinjection, many applications for Dutch elm disease, as well as Sycamore anthracnose can be controlled for as long as three years with one macroinjection application.

Still, arborists recommend reminding clients that, while treatments may last a long time, macroinfusion is only meant to control diseases – not cure them. "Injections are not vaccinations," says Vic Foerster, sales manager, West Michigan Tree Service, Grand Rapids, Mich. "When you think of a tree getting a shot, which injections look like, clients can sometimes confuse them with some kind of tree vaccination where you’re introducing an antitoxin that the tree will retain forever like a person would. That’s not the case, so control is always the optimal word for any disease treatment in particular."

To educate clients on tree injection, Foerster and other tree care professionals leave informational fliers during visits. "We have a lot of preprinted information that we leave with our clients during estimates to introduce them to the concept and there’s verbal communication that’s going on all the time," Foerster says.

Prosser and Foerster both note that macroinfusion is more expensive that microinjection, but is often requested by clients who are willing to spend the money on "heirloom" trees or landscape staples they want to keep healthy. Additionally, Prosser notes that his company offers clients a guarantee on the health of their trees, refunding clients’ money if a tree dies from the disease for which it’s been treated.

"Our cost for a Dutch elm disease treatment that will last three years is about $170 for an average tree and we charge in the neighborhood of $400 for that treatment," Prosser says. "We do raise our prices to cover our expenses and also to cover the loss to our guarantees. We know we’re going to lose about 7 percent of the trees we treat for Dutch elm, so we’ll mark up the cost about 10 percent to cover the guarantee."

Regardless of whether a tree care worker is making a micro or macroinjection application, most contractors agree that the key to proper applications is good education.

"The department of agriculture in our state mandates several hours of training for injection application," comments Steve Geist, plant pathologist, Swingle Tree & Lawn Care, Denver, Colo. However, the majority of Swingle’s technicians perform soil injection applications, which require only a few days of classroom training and then on-the-job supervision. For trunk injection work, such as treating Dutch elm disease, more education is required. "Trunk injection is seen as a prestigious job at our company," he comments. "Students or applicators who show exceptional aptitude are given an extra day of training in-house and almost a week of intensive training out in the field. I work with them one-on-one to make sure they get my full attention and learn all the specific steps."

Foerster agrees on the importance of education. "The training and education available now as compared to 20 years ago has leaped ahead," he comments. "But there can be instances where the products are so easy to use that anyone can use them, so you have to make sure that you have the insect and disease knowledge to accompany the mechanical knowledge. Injection is an important part of what we do to take care of trees, but education is key."

The author is assistant editor of Lawn & Landscape magazine and can be reached at lspiers@lawnandlandscape.com.