Wooly adrlgid

Asked April 16, 2016, 2:22 PM EDT

I have two large hemlocks that are showing signs of egg sacks. I heard that you can treat large trees at the trunk. Any suggested products or treatment?

Luzerne County Pennsylvania

1 Response

I have the same problem. It's sad to see a 100 foot giant destroyed by an invasive insect. I've researched this topic and found two ways to go. Our Carbon County District Forester, Frank Snyder, recommends a systemic pesticide called Safari. In Pennsylvania it has to be applied by a tree service with a licensed applicator. It works for one to two years according to Frank Snyder. You will need to keep up the Safari to prevent re-infection from neighboring trees.
The other remedy is biological control. There is a Japanese lady beetle, a natural enemy of hemlock woolly adelgid (HWA), that has been approved for release to control HWA. An outfit called Tree-savers in Scranton sells the beetles for $2.50 each. It takes about 100 beetles to a big hemlock. If your hemlocks are not too far gone, you can consider the biological control. You can estimate the damage on your hemlocks by looking at the trees. Notice desiccated limbs and twigs, missing needles, and a ragged looking canopy. Stand where you can see the whole tree and see if the upper canopy is healthy or thin and lacy.
I recommend calling a licensed pesticide service and getting an estimate and an idea of what you are in for if you go the chemical route. You can also call Tree-savers to see what they recommend.
I decided in favor of the biological control because I have a bunch of young hemlocks in my woods. I can't treat every one of them with Safari, only my big tree. The beetles, on the other hand, can move from tree to tree and begin getting HWA under control.
These are the two long term choices. For a short term pesticide application, some tree services are using horticultural oil and Sevin. These pesticides will kill the HWA currently on your trees, but not ones that might re-infest your trees in the future.