To most laymen, trees are just “there.” Year after year, they sprout leaves, get flowers and fruits, go dormant . . . and then repeat the cycle in the spring. But professionals know that the care and feeding of trees is a major undertaking. You need to be concerned with pests, fertilization, feeding, disease control . . . at times, it can almost be like raising a child! There are several approaches to treating trees.
Although spraying was a very common method many years ago (and still has its place in the tree care spectrum), the technique is often labor- and capital-intensive.
If you’re in the Midwest and dealing with certain leaf diseases, you’ll need to spray twice each spring. The elm leaf beetle (common to California) goes through three hatching cycles every year— which means that conscientious applicators will spray three separate times.
Timing of the spraying program is also critical. Spray in the middle of the ladybug’s feeding cycle, and you risk killing off a natural form of pest control—a beneficial insect that can eat up to 25 aphids per day.
Environmental concerns are very real as well, because these chemicals are poisonous.
Mike Ventura, president of Ventura’s Tree Management, Cucamonga, California, sums them up.
“If the wind is more than 15 mph, the sprayed chemicals can drift away from the trees and cause phytotoxic reactions on turfgrass and other plants,” he says. “They can also drift into nearby pools of water, thereby contaminating them. And there’s always the risk of people feeling sick from the chemicals you’ve used. Spraying sounds simple, but I think it can be a wide-open ticket for trouble.”
Wind drift can also hamper the chemicals’ effectiveness on-site, simply because a portion of the “dose” simply doesn’t reach its destination. There are dollars-and-cents concerns as well, says Jim Haas, owner of Lincoln Tree Service, Lincoln, Nebraska.
“Investing in a sprayer system—including the tanks, the motors, pump and truck—can run around $45,000. You also have to consider the annual costs of maintenance, winterizing the equipment and warehousing it in the off-seasons.”
Soil-drenching is another approach, and it’s a self-describing one: chemicals are diluted with water, and then deposited around the base of the tree.
“Drenching is a reasonably effective method,” says Dr. Roger Webb, president of Tree Tech Microinjection Systems, Morriston, Florida, “but there are several very practical concerns about it.”
One of them, says Nate Dodds, president of Mauget, Arcadia, California, is that you need to put a large amount of chemicals into the ground . . . and even the “proper” dosage might not be enough. For one thing, he says, “Anything else in the ground is going to be in competition with the tree’s roots for the elements you’ve added.” Will the tree actually be able to absorb what it needs? Hard to tell.
The ability of the ground to absorb moisture is another determining factor in soil drenching. It’s fine if the soil is dry enough to quickly take up what you’ve added. But if it’s not, you might actually experience product runoff—with the associated risk of poisonous chemicals finding their way into drainage systems and possibly into a municipal water supply.
That’s not a far-fetched idea. According to Roger Webb, the New York State Department of Environmental Conservation found imidacloprid (an insecticide often used in agriculture, forestry and for ornamental plants) residue in private wells on Long Island about five years ago. Linked to excessive use of the bug killer, that discovery led to a ban on soil-drenching in that community.
Another difficulty is that this technique won’t work on fungi or certain insects, says Wayne White, a certified arborist for Emerald Tree Care in White Lake, Michigan.
Another approach to pest and disease control is the use of chemicals mixed with a bark penetrant (many times a non-ionic surfactant, such as Pentra-Bark). Webb says the penetrant is designed to open gas exchange pores in the bark, in order to let the applied fluids pass through the underlying xylem and phloem layers, and thus into the tree’s vascular system. He adds that the procedure is a way to control bark-feeding insects—you can kill them as they are boring into the tree, or later, as the adults are emerging.
There are many good applications for this technique, says Chip Doolittle, ArborSystems LLC, Omaha, Nebraska, but you can’t avoid the fact that it’s still a form of spraying insecticides, and many arborists aren’t convinced that the benefits outweigh the risks. “It’s one thing to put it on leaves that are 20 or 50 feet in the air,” Doolittle says, “and another thing to put it on bark.”
Webb adds that good safety precautions include wearing a protective full body suit, an aspirator and eyewear while spraying the trunks. He adds that it’s common to repeat the procedure every three weeks until the project is complete.
But a midst these messy, awkward and potentially dangerous techniques is one that’s economical, easy to use and relatively safe: tree injection.
The technology behind tree injection is actually centuries old, says Dodds.
He says the first documented use of the method can be credited to Leonardo da Vinci. In the courtyard of his home in Italy, Dodds says, Leonardo had several fruit trees, which were frequently the targets of neighborhood thieves who wanted to have fruit without the work of growing it themselves.
In order to discourage their pilfering, da Vinci bored holes into some of the trees and forced arsenic into the holes. The trees’ vascular systems transported the poison and deposited it in the fruit.
You can bet it didn’t take very long for the thieves to start hitting someone else’s orchards!
Drilling small holes around the base of a tree.
Today, although we frown upon poisoning fruit poachers, that ancient technology is still an effective means of controlling non-human pests and diseases in trees.
Essentially, the injection method is similar to the use of IV medications in human patients. Although oral antibiotics are useful treatments, direct injection of them is often more appropriate. The patient’s circulatory system will carry the medication throughout the body and take it directly to the source of the problem . . . bypassing the need to go through the digestive system and other tissues.
Trees are similar in that regard. Fungicides, pesticides, fertilizers and other chemical treatments are often more effective when they are injected, because they go directly to the plant’s vascular system and don’t have to rely on slower absorption through roots or leaves.
Although injection technology continued to be used over the next several hundred years, it got a huge boost in 1948, when Jim Mauget was recuperating in a hospital, receiving post-op intravenous treatments. It occurred to him that a similar method might be practical for use in trees.
Mauget’s passive system is touted as being the least invasive and least traumatic method for putting chemicals into a tree. According to Nate Dodds, the concept came from Dr. Alex Shigo, whose extensive research determined the effectiveness of making a small, shallow wound, and allowing the tree’s own transport system to take in the chemical mix at its own rate.
Today, that basic idea has been adopted and adapted by several other companies. And although the products differ in the details, they have much in common.
Tree injection is a fairly simple process. The applicator assesses the tree to determine the exact nature of the problem, then measures the tree’s diameter in inches at chest height. Divide that number by two, and you’ve determined the proper number of injections needed to do the job.
With the Mauget system, applicators drill a series of small holes around the base of the tree, using a surgical quality high-helix bit to minimize damage to the tree cells. The injection tube is inserted, and the applicator squeezes the top of a small container of pre-dosed chemicals to gently pressurize it.
It can be used to administer antibiotics, fertilizers, fungicides, insecticides, and combinations of insecticides/fungicides to avoid the need for multiple injections.
The equipment needed for the job is pretty simple:
• Cordless drill
• Tape measure
• Protective gloves
• Rubber mallet or similar tool
Uptake rate depends on many factors, such as the type of tree and its particular cell structure, the tree’s ability to move large volumes of liquid through itself . . . even the time of year. Dodds points out that it’s important to recognize the ebband-flow cycles of the tree. In winter, it will be dormant; but in spring, as it grows new foliage, the vascular system will be more active, drawing in loads of water each day.
Kirk Floyd, a plant healthcare specialist with ArborCare, Inc. in Rockville, Maryland, has used this injection system. “The Bethesda Urban Partnership had been treating its many trees for powdery mildew by spraying three times a year,” he says. “Previously, the spraying company had to drive trucks through town in the middle of the night to avoid pedestrian traffic. And there were many complaints about the spraying and its aftermath. With Mauget, my crews were able to treat the trees in the middle of the day, and complaints went way down. Although my bid price was higher than the sprayer’s, the partnership is happier with my results.”
ArborSystems offers the Direct- Inject QC system, which forces a small amount of chemicals just underneath the tree’s bark.
It differs from Mauget because it requires no drilling into the tree, and uses pressure (rather than gravity) to deliver the chem icals.
Applicators use a punch tool to remove a small plug of bark from the tree, and then insert a small, self-sealing rubber device into the tree. (It acts much like the rubber plug inside a basketball’s inflation hole.)
Chemicals are loaded into the delivery tool, and the applicator simply forces the injection needle through the rubber seal and squeezes the handles. The chemical load is deposited into the tree’s cambial layer (under 3-5 psi pressure), without disturbing the tree’s vascular system.
Reportedly, this type of shallow injection doesn’t damage the sapwood and prevents air from entering the wound. Proprietary chemicals include various insecticides, fungicides, nutritional supplements and growth regulators.
Wayne White has battled the emerald ash borer for many years. He prefers the ArborSystems product for this application because, “I need to protect the area under the bark, along the whole trunk. If I went in too deep, I suspect the chemicals would go up through the tree, instead of ‘sideways’ to protect the bark. It’s quick, too,” he says. “Usually, I average more than 100 trees per hour.”
You might also consider using the Tree Tech micro-injection system. Its basic operating principle and injection technique are similar to those of Mauget, but Tree Tech offers the option of pressurizing the load or simply allowing the chemicals to drain into the tree by force of gravity.
Webb notes that this choice will have a definite effect on uptake rates: “If you inject a water-based solution under good conditions—a warm, sunny day, with adequate soil moisture and a good vascular system—the fluid will drain in about 15 minutes if it’s pressurized, and 30 to 45 minutes if it’s not.” He adds that a fungicide (using a heavier solvent) could take 30 minutes or more to drain under pressure, and up to several hours without it.
“I think it’s a wonderful design,” says Ron Danise, a certified arborist, educator and owner of Southern Organics in Charlotte, North Carolina. He has deep concerns about the environment, and prefers to avoid chemicals when possible. But, “This technique uses 2 or 3 mL per injection—that’s about 2 or 3 ounces for an entire tree. It maximizes the benefits and minimizes the side effects,” Danise says.
“Plus, the trucks and other equipment used in spraying leave a bigger carbon footprint.” Spraying can use thousands of gallons.
Obviously, there are many ways to treat ailing trees, but direct injection seems to have an edge in terms of ease of use, applicator and public safety, and productivity. And it offers a benefit to your clients as well.
“The response time of an injected tree is very rapid, compared to other methods. You can often see results in a week or two,” says Dodds.