In the 1930s, when William Arthur Roach was researching his pioneer study on “Plant Injection as a Physiological Method,” he reported that Leonardo da Vinci (1452-1519) was, apparently, the first person who conducted systematic experiments with trees being injected with liquids. But, genius that he was – he’s the quintessential “Renaissance Man” – Leonardo was following the thinking and tinkering of others. There were 12th Century Arabs, Roach reported, who described techniques for introducing solid substances directly into plant tissue to add perfumes, colors and medicinal qualities to fruits or flowers.


Obviously, in order to do that, or even guess about such things, some knowledge of the internal hydraulic workings of plants needed to be understood.

It wasn’t until about 500 years later that the human body’s vascular network was grasped in a similar way. It was 1628 when the theory of circulation was published, explaining what your heart was doing, and how the blood was carried by the veins and arteries. Those veins and arteries equate to xylem and phloem in trees … well, not exactly, of course. But a tree and a human each have a network of conduits conveying vital fluids throughout.

Photo courtesy: ArborSystems

It wasn’t until the 18th Century that vaccinations became common; it took 100 years for practical application of the knowledge of human circulation to reach the level of knowledge of those Arabs who modified the colors of flowers by tinkering with the plants’ veins.

But just as leading tree biologist Dr. Alex Shigo came to write, “We are bags of chemicals, and so are trees,” cross-species awareness occurred to Jim Mauget when he was getting his own xylem jabbed in the form of a post-operative IV drip in 1948. At the time, giving a tree an IV couldn’t have been much different than was described in texts by researcher Roach, when he was experimenting with adding nitrogen compounds to apple trees.

Roach describes a sort of vacuum-driven infusion device that was very likely cutting edge technology in 1936 – a 40’’-tall contraption sitting in a water bath. He and his partner’s “rapid continuous vacuum extractor” included a flask of 85% alcohol solution, an extraction vessel, a condenser with suction by means of a rotary oil air pump, separated by a calcium chloride trap and a gravity-driven non-return valve. The condenser was cooled by 30 feet of copper tube. The device had a thermostat to heat its water bath, and a means to regulate bubbling of the alcohol solvent.

Not really a suitable device to use on a house call for a mow’n’go crew.

But by ’64, Mauget and his partner Dale Dodds had developed a product and injection device with which to apply it called the Inject-A-Cide B, and the tree microinjection business was begun. From that tiny acorn a mighty oak has grown, because there are many good candidates for tree injection services.

There is an increasing environmental health awareness about spraying trees that decreases the instances when it’s appropriate to cover the crown with pesticide or fertilizer. Injection can be a welcome alternative for the customer, their neighborhood or the green industry professional himself who doesn’t want to come home covered in pesticide mist at the end of the day.

“The more they regulate spraying, the more people will look to injections,” says Chip Doolittle, president of Arbor Systems of Omaha, Nebraska. Some landscape contractors are simply looking for new ways to expand their business beyond their present services, and are looking for new ways to feed a tree and control its pests and diseases.

It doesn’t take a da Vinci to see the difference between having to hurl so much chemistry into the air and letting the natural hydraulic siphon action of the xylem and phloem distribute it through the tree. Tree injection is a method that can be applied in windy and wet conditions, and over open water. Ground applications of pesticides and fertilizers have issues regarding leaching, root competition and moisture, among others. Foliar applications are complicated by drift and the high-cost of equipment needed to apply what is a much greater amount of chemicals.

The benefits to helpful insects and other predators are also obvious. Only insects eating treated plant material ingest the injected chemicals. Consequently, the poison doesn’t really travel up the food chain. For example, a boring insect that dies inside a tree is unavailable to birds. A leaf-eating insect becomes unpalatable, and holds a small amount of chemical as compared to the amount that may have had to be sprayed to be effective.

Photo courtesy: Tree Tech

Caring for the environment by using tree injection is a characteristic sought in protecting exotic species under the meticulous needs of zoos and arboretums. Also, it is those characteristics that are vital in the fight against exotic species. That fight is dire. Arnold Farran, director of research at Mauget Company, says, “Exotic species are coming in all the time.”

Primary on that list is the Asian longhorn beetle, with a USDA eradication program covering a swath of the country from New York to Chicago. Various tree injection compounds are being used to suppress, contain, kill or inoculate against other pests also, with uses determined by regional regulations.

Targeted insects include adelgids, armored scales, aphids, black vine weevil larvae, elm leaf beetles, fall webworm, flatheaded borers (including citrus borer, bronze birch borer, emerald ash borer and alder-birch borer) and longhorned borers (including eucalyptus and cottonwood borers), Japanese beetles, lacebugs, leafhoppers, leafminers, mealybugs, psyllids, pine tip moth larvae, royal palm bugs, sawfly larvae, spider mites, soft scale insects, thrips, white grub larvae (such as Japanese beetle larvae, chafers, June beetle, Asiatic garden beetle and oriental beetle) and whiteflies.

Various fungicides are being used for oak wilt, Dutch elm disease, sycamore anthracnose, cedar apple rust, apple scab, and other leaf diseases of flowering crabapple. They are also being used for the suppression of fungi and the control of other plant diseases, including rust, powdery mildew, leaf spots, bacterial blights, wilt, root rot and cankers of various types.

In Guam, Hawaii and the Caribbean, injections are saving cycads, says Farran. In January’s USDA Exotic Insect Forum, the study that he and Dr. Terry Tattar did is being presented, describing going toe-to-scale with Aulacaspis yasumatsui. The research trial was first reported in last February’s Irrigation & Green Industry magazine. The abstract of that research study says, “Asian cycad scale populations were reduced in Imicide-injected cycads by 32% after 60 days, while scale populations increased by 268% in untreated control cycads.”

The leading use of tree trunk injections is in the Asian longhorned beetle battle; the USDA is injecting those many millions of trees with Imicide. Developed by the Bayer Company, imadcloprid is the active ingredient in Imicide, which has been formulated by the Mauget Company for use in micro-injection. Arbor Systems’ formulation of imadcloprid is Pointer. Bayer markets imadcloprid under the brand name of Merit, and it is otherwise used as a soil drench as well as a spray application, depending on the need and circumstance.

Photo courtesy: Mauget Company

In addition to the needs of the client, green industry professionals should consider their own needs for micro-injection systems. Often, injection compounds are prepackaged units of fertilizers, insecticides and fungicides. They are sold in sealed containers – labeled or color-coded and premixed, so the possibility of human error is kept to a minimum. Some products are sold in larger quantities, with some formulations engineered to be a cocktail of insecticides and fertilizers. An implant method deposits a gel-cap marketed as Acecap.

Different methods apply compounds under different pressures. Some are literally injected while others wick into the tree, more infusion than injection. Also, each supplier’s specific injection device will vary. A Mauget capsule is pressurized in the plunger action of pressing the top. Tree Tech’s injection unit is seated by the tap from a mallet, then the chemicals are pressed through their device and into the tree.

Most tree injection methods depend upon drilling a hole into the outer rings of the tree. Arbor Systems has a different approach. Doolittle, mounting a challenge raised in a five-day seminar with tree guru Shigo, went out and developed a different technique. Their Wedgle injection system uses a wedge-shaped insertion needle and a hand-pumped injection unit that penetrates the bark only.

There are a number of injection options for contractors, but often injection by some method is the only option.
The Hemlock Woolly Adelgid Action Team, a group of scientists and land managers created to fight the pest in Southern Appalachia, says on its “Save Our Hemlocks!” website that tree trunk injection “is the only method available for trees near open water, because trunk injection prevents contact between the water and the chemical.” Also, two New York counties in the Asian longhorn beetle battle prohibit anything but tree injection.

While circumstances grow for trunk injections, there may be a push to apply services when they aren’t warranted. Customers may well insist on tree injection, having heard or read about it, but it’s not right for every circumstance. Utah State University extension forestry specialist Michael Kuhns cites a parallel: “For example, some people want their trees topped, yet it's bad for the tree and shouldn't be done.”

Even though some green industry professionals are as wary as some customers might be of applying human and veterinary care concepts to trees, many of the manufacturers of micro-injection systems have detailed instructions and information on their websites, and some offer online seminars and/or certifications. In addition, technical support is just a phone call away. All of which will help a good sales staff in this service-provider business. From the TreeUtah newsletter, by way of Utah State University, Kuhns writes that green industry professionals need to be informed:

“1) Persons selling tree care services or products need a thorough knowledge of trees, and how to care for them. 2) Don't sell a product or service unless you know how (and if) it works. 3) Be skeptical before adopting a product. Ask for and read published scientific literature. 4) Avoid selling services that do not work or that do harm. At least warn people if a desired treatment is unnecessary or harmful.”

Some smart person may be finding better ways than piercing the bark – transfer agents at the cambium tissue possibly – to deliver the needed mixtures. Fresh applications are at the door such as plant growth regulators, to stop that olive from littering like a bird’s nest into the koi pond or to keep that ficus from getting up and under the balcony and sending its roots across the yard into the septic tank.

Plant growth regulators, Tree Tech’s Snipper deflowering agent for example, work like giving a birth control device to a tree’s male and female flowers. Hormones prevent the sex cells from being available when it’s time to complete reproduction, says Dr. Roger Webb, Tree Tech founder.

“We give it a headache,” Webb says, coming back to the idea of the tree/human parallel.

Maybe in that cyclic way that both ideas and nature have, someone will find a need for plants in their landscape to change color, or have a scent, or an added medicinal property, much like those 12th Century plant tinkerers. Green technologies may have both vital and cosmetic demands ahead. Who knows what would come of the ability to have mulberry trees smell like roses or have them match the color of liquidambars … or a customer’s shutters? Perhaps there’s a pest or virus whose infestation is avoided by a targeted change in color or smell. Maybe the result is the know-how to make the bark of common pines mimic rare Pacific yew trees and aid in the fight against cancer.

Such a thing might make Leonardo da Vinci quite proud.