Hemlock wooly adelgid – Insecticidal control options

Q: We own a home in north Georgia and have hemlocks located twenty feet from a small creek. The trees are infested with wooly adelgids. Last year we sprayed them but could not get to the tree tops. We also have one large hemlock, further away, on which we drenched Bayer Advanced Tree & Shrub Insecticide. Since the smaller trees are near water, can a handy homeowner use Pointer insecticide to kill adelgids on them?

A: The imidacloprid chemical found in Pointer and the Bayer drench are effective at controlling hemlock woolly adelgid. The challenge is getting it to the tree needles where the adelgids do their damage. Pointer uses small capsules of insecticide inserted in the trunk at the base of a tree.

Chris Hastings, with ArborMedics, says when he does use Pointer capsules it is common for the insecticide to not enter the tree. The capsules do not inject the liquid but rather apply slight pressure and wait for the tree to suck it up. If the vascular system is not active, when a tree is dormant or stressed, the insecticide will not be pulled to the top.

Art Morris, with New Urban Forestry, says that with the Pointer system it’s a little tricky to drill a hole just deep enough to hit the tree’s xylem layer without going too far.

As you know, imidacloprid is toxic to invertebrates like fish. A Bayer representative recommends that their imidacloprid product be drenched onto the soil no closer than twenty feet from a body of water. This leaves the Pointer system as the only homeowner alternative for small trees.

You are welcome to try it yourself but remember that an ISA certified arborist can use a pressurized system that might be more effective.

hemlock adelgid