AB-The Micro & Macro Wave: Micro vs. Macro - FOCUS: Tree Care

Just as blood flows through human arteries carrying oxygen, a substance called xylem moves through trees’ vascular vessels circulating sap.

Tree and human circulatory systems also bear similarities when it comes to treating infection or illness. As intravenous injections are administered to people for the purpose of conquering disease and promoting recovery, microinjection and macroinjection treatments can be introduced into trees to combat insects and diseases or add micronutrients.

Tree injection treatments provide technicians with additional options when treating sick or malnourished trees. They also may be safer on the environment and the operator administering the treatment because the potential for drift and product exposure is reduced, pointed out Nate Dodds, president, J.J. Mauget, Arcadia, Calif.

But to choose the right treatment method and to ensure that it works properly, technicians must understand how these treatments work and learn how to accurately dispense them.

ARSENIC & OLD LACE. Though tree injection treatments seem to be growing in popularity today as suppliers develop pesticides available in injection formulations or produce new methods of infusing products into trees, they are actually mature procedures, dating back to the 16th century. In fact, Leonardo da Vinci was the first person to utilize a tree’s veins to transport chemicals. "Da Vinci injected arsenic into the apple tree in his front yard to discourage passersby from stealing its fruit," Dodds explained.

Despite the fact that they are called "injection" treatments, the process in trees is more like an IV, where a balanced, slow-dripping bag of glucose solution, for instance, is introduced into a person’s circulatory system, pointed out Roger Webb, president, Tree Tech, Morriston, Fla. "Tree injection isn’t like in the doctor’s office where he is forcing a material into your body in a short period of time," he explained. "It is more like an infusion process where the speed of evacuation isn’t the primary concern. It’s about the proper access of fluid into the tree’s circulatory system. The tree will then uptake the product, and this can occur with or without pressure."

Injection treatments control a wide range of vascular-feeding insects. "Even bugs sucking on a leaf are tapping into a tree’s sap stream and can be controlled this way," Dodds said.

These treatments also can manage diseases that exist in the water-connecting tissue of a tree, added Tom Prosser, president, Rainbow Treecare Scientific Advancements, St. Louis Park, Minn., stating that macroinjection focuses on three major tree diseases: Dutch elm disease, oak wilt and sycamore anthracnose. "Although sycamore anthracnose shows symptoms on tree leaves, 95 percent of its lifecycle is in tree twigs and stems, which is why injection treatments can control it."

Certain products that are sprayed, but risk breakdown due to sun and wind exposure, also can be injected. As long as a tree’s vascular system functions properly, a product’s residual increases due to this lack of outside exposure, commented Chip Doolittle, president, ArborSystems, Omaha, Neb. "This could be a 10-day outside residual vs. a 12-month residual with injection treatments," he said.

Contractors who use injection treatments also claim that less product is misplaced. "You’re utilizing a tree’s own transport system for distribution," remarked Jerry Naiser, president, Arbor Consulting, dba Tree Masters, Austin, Texas. "Since each injection point is independent, there is less chance for waste due to leakage. No air, soil or groundwater contamination occurs. No overspray, no drift, no spill, no waste."

But while there are benefits to using injection treatments, Rex Bastian, vice president of field education, Hendrickson – The Care of Trees, Wheeling, Ill., stressed that no one product or application method can work every time, particularly with trees. "It all depends on the tree," he said. "A lot of people want to make treating insects and diseases on trees simple, but it’s not. You have to figure out what works best based on the specific tree and the specific problem. As contractors, we have to be familiar with all techniques and know their advantages and disadvantages. And we have to use treatments in a responsible manner."

MICRO & MACRO. The size of the holes used to administer products in trees is the main factor that distinguishes microinjection from macro-injection. Hole size is typically at or below ¼ inch for microinjection and at or slightly above ¼ inch for macroinjection, according to Bastian, who uses both methods in his tree care program.

In microinjection, each injection point around the tree is independent and in macroinjection, each injection point shares a common product supply line, pointed out Naiser, who also uses both treatments, but prefers microinjection because in macroinjection "the applicator is responsible for mixing products and making sure that no leaks develop," he said. "With macro, it is possible to lose all product on the ground, if you are not carefully monitoring the tree."

But macroinjection involves the distribution of more product into the tree – 30 to 60 gallons, Prosser explained, while microinjection uses anywhere from 2 to 14 milliliters of product, Webb said.

There is some debate among contractors about the amount of product injected into a tree through injection and what it means in terms of length of disease and insect control. Jim Rediker, owner, Scenic Hills Nursery, Kerrville, Texas, who specializes in oak wilt treatment and prefers macroinjection, said more product means better distribution throughout the tree, because "how high up into the tree can that small amount of chemical [in microinjection] reach?"

Bastian, on the other hand, said length of control isn’t a result of the delivery approach. Instead of being a function of the type of treatment or amount of product used, he said product residual is a result of the chemistry employed. "Some materials can be injected and give a longer period of control than others, regardless of whether they are administered through micro or macroinjection," he said.

In terms of cost, most contractors agree that macroinjection can cost less than microinjection, but more time is needed to administer the product. A complete set of reusable equipment, including 75 tees, a pump and tubing, can cost approximately $200. And treating an average tree can cost between $50 to $130, depending on the process and what disease is being controlled, Prosser said.

To treat an 8-inch diameter tree for insect control with microinjection, the pesticide can cost between $8 to $12, and an injection gun can range from $100 to $500, Doolittle said. Dodds figured it differently, stating that the cost of microinjection treatments can be anywhere from $1.25 to $2 per a tree’s diameter inch, plus the cost of labor. While microinjection costs more, "a typical 20-inch diameter tree taking 10 capsules can be treated inside of five minutes," Dodd said, pointing out time saved on the job.

"Although microinjection packaging may cost a little more, money is saved on labor and equipment because it does not require the intense monitoring that macroinjection does," Naiser related.

TIPS OF THE TRADE. Many of the hot and cold feelings contractors have about either macro or microinjection may derive from mistakes made during application. Webb said the most common mistake is drilling too deep or not drilling deep enough into the tree. "The first movement you feel is the drill torque down at the outer xylem," Webb explained. "It will feel like a different substance. Once you hit this change in drill torque, withdraw from the tree and check to see how far the wood fibers have come up through the spirals of the drill bit. This is where the waste wood is forced into and up behind the tip of the drill bit. If the waste wood has come up the drill bit channel a ¼ inch, then stop. If it’s less, go a little deeper. It’s a technique that is developed through experience."

Poor timing also can negatively impact injection treatments. Most contractors and suppliers recommend injection treatments in early spring just after bud break when a tree becomes more active. Also, Naiser said the best uptake of product will occur in the morning on sunny days.

"We don’t recommend injections in hot climates after 11 a.m. because a tree is experiencing maximum water flow and floods of resin will bleed out of the injection holes," Dodds warned. "Contractors should stop doing injections before the heat of the day."

Also, burn risk increases with some products when applied in hot climates, pointed out John Fishbach, Medi-Ject Tree Injection System, Lincoln, Neb. "The transpiration out of leaves is so great in the heat that sometimes they will suck in the solution so fast that one or two branches will burn," he said. "There is less risk of burn closer to fall. Even though the tree may be shutting down, injections at this time ensure that iron and zinc will be there for the tree next spring."

Contractors and suppliers also recommend the following injection tips:

• Heavy, thick or loose outer bark can be carefully shaved to form a smoother injection point and to ensure that the drill penetrates to the xylem.



• A slight downward angle hole is recommended for complete product drainage.



• Use a new drill bit after every 40 units. A sharp bit will cut cleaner, with no heat, thereby giving maximum product uptake.



• Disinfect the drill bit between trees with Lysol or a 20 percent solution of bleach, then rinse the bit with clean water.

Humans tend to put trees under a lot of stress, so treating them correctly is crucial, Dodds said. Contractors should learn about these treatments and add those they become comfortable using to their insect and disease control arsenal, Bastian said. "There isn’t one perfect system for treating trees," he explained. "As long as you become educated on all your viable choices and can present this information and all the risks and benefits to your clients, then they can make a final decision on the care of their trees that they are comfortable with."