According to Brewer, however, it usually comes down to product preference. He sees good success with Arbotect 20-S from Rainbow Ecoscience on beech leaf disease, but that product is specifically indicated for macro-infusion only. “There’s not really much that can only be treated through macro-in- jection anymore,” he said. “It comes down to product choice… It’s not about one being more effective than the other. It’s just how you choose and what research you choose to use as your system.” Macro-infusions may also outperform micro in terms of their speed of dis- tribution and mobility in trees, Belter said, especially to the terminal ends of long branches. Just beware that if the chemical is phytotoxic, you could see a higher risk of it actually killing the tree. “Regarding large trees or long-term control,” he said, “the chemical for- mulation and the allowed label rates matching actual severe infection rates of a tree with said body mass is a deci- sive factor.” Macro is typically not as effective when uptake is slowed by high soil moisture or on very hot or cold days, and trees with compromised vascular systems may also not see great results.
UNDERSTANDING THE RISKS: WOUNDS, PRESSURE, CROSS- CONTAMINATION
The QUIK‑jet is a cost effective injection tool built for lower‑dose treatments, and it can also serve as a diagnostic device to evaluate tree health and vascular function.
While micro- and macro-injections can easily be credited for saving countless trees, the techniques aren’t without risks. Drilling creates wounds, however small they may be, and repeated treatments around the tree year after year can add up to a lot of wounds. Macro-injections, for example, can require 75 injection sites on one 50-inch tree. According to Belter, the pressure re- quired for some of these injections may also be problematic.
While micro-injections make up the vast majority of his company’s treat- ments, Cleveland said he still regularly uses macro for systemic fungicides for Dutch elm and oak wilt. He’s also seen better results when treating sycamore anthracnose. “There are micro-infusion treatments for it, but we’ve just had better results with the macro-infusion,” he said. “You pay more for the macro, but it lasts lon- ger and it’s better.”
chemical, macro-injections use a high volume of water-diluted solution — think gallons instead of milliliters. “When Dutch elm disease came through and wiped out block after block of trees, there wasn’t any way to stop it,” Cleveland said. “So, when this macro infusion came along, it can pre- vent the disease from spreading. It’s basically an inoculation or a vaccine that lasts two or three years.”
20 | Summer 2026 ArborTIMES ™
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