Micro-injection has become the new delivery standard for many pesticides, micronutrients and fungicides, delivered by drilling a small, shallow hole around the root flare.
Micro Vs. Macro Making the Right Call with Tree Injections By Matt Smithmier
Even in the age of the laser-guided “in- telligent sprayer,” the shift away from broad-spectrum foliar spraying is only ac- celerating. First, there’s the issue of simple ineffective- ness: After all, depending on wind, sunlight and the time of year, a good number of those chemicals may never reach the target plant. These sprays also like to go wherever they want — including where they shouldn’t: A 2024 study from the Illinois Department of Natural Resources looked at 185 differ- ent woodland, grassland and wetland sites across the state and found 41 different chemical compounds — with at least one found at 97% of the sites. Of course, liability for arborists is also high- er with spraying, which means increased insurance rates and more regulatory hoops. And with the EPA acknowledging that by- stander exposure should be expected even under proper application , pros face a level of public scrutiny like never before. “They assume if you show up with a spray truck, you’re spraying Agent Orange … and their kids are going to have six toes,” said Chip Doolittle, president of Omaha-based ArborSystems . “So, you’ve got a giant
weight around you if you’re just spraying trees.” Of course, as spraying has declined, trunk injections have grown: From some of the first pre-filled capsules in the 1960s to the innovative low-pressure, micro-injection tools of today, arborists are increasingly implementing these more precise, environ- mentally contained alternative treatments for insect control, disease prevention and nutrient administration. Today, arborists are taking advantage of a variety of micro-injection and macro-injec- tion treatments, but when is each one most appropriate — and what should arborists consider before choosing? MICRO-INJECTIONS: PRECISION DELIVERY FOR MODERN PHC Bret Cleveland is the owner of Urban Tree Specialists in Kansas City, Missouri, and has seen the rapid evolution of plant health care firsthand over the last 25 years. “When we first started and were applying iron, we were just drilling holes around the base of the tree and dumping straight chelated iron in,” he said. “The tree would turn green
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