by Richard Gardner
"Drill and fill" is a simple, volunteer-safe way of killing Ailanthus altissima, or tree-of-heaven, during nondormancy. It is designed to replace hack-and-squirt cut/treat and basal bark spraying for stumps.
The materials are concentrated (purple-capped) Roundup® (50.2% active) Weed and Grass Killer, a pair of nitrile gloves, a cordless drill with a 3/8-inch bit, a spray bottle, a marker, and a tape measure.
Wrap the tape measure at a comfortable working height around the circumference of the tree to be killed. Mark every 2 inches. Drill 1.5-inch-deep holes at every mark. Spray the concentrated Roundup into each hole. In a few days the leaves will start to turn yellow. Within a week or so, the leaves will turn yellow and start dropping. This will continue until no leaves remain. After a few months, test the tree by scraping between the holes to make sure there is no living (green) under the bark. If there is green, drill a hole in the green area and spray in more concentrated Roundup.
This method can be done whenever the tree is not dormant—from early spring, when the tree is coming out of dormancy, to before leaf-drop in the fall—and is designed for mature trees. However, it can be adjusted to trees down to about 1-inch diameter by using proportionally smaller drill bits. I have killed trees with diameters of 1 to over 60 inches in a single treatment.
During dormancy, there are still a couple quirks. It appears that placing holes around the base of the tree, taking care to drill into all obvious roots, is more effective than at comfortable working height. Make sure to observe these trees for a couple of years to check for clones. If necessary, treat the clones.
If the treated tree is near a building or other place where its falling could be a hazard, it should be cut down 6 months to a year from treatment. Otherwise, it may snap off at the drill holes during a storm.