hemlock maintenance

Asked April 25, 2016, 1:48 PM EDT

I'm noticing some wooly adelgid in my hemlock hedge along with lighter green foliage in a few areas. Are there any chemical sprays or horticultural oils or soaps effective now? If so , what is the recommended application schedule? Thanks for your assistance.

Chester County Pennsylvania

1 Response

Hemlock Woolly Adelgid (HWA) is infecting hemlocks in Pennsylvania at a high rate. I just found it on two giant hemlocks and on five small ones in my woods.
There are several chemical treatments and one biological treatment.
If you treat with a pesticide, you can use sevin or horticultural oil for a one time treatment. That will kill the infestation currently on your tree. You can opt for a systemic called Safari that will give you one to two years protection and must be applied by a licensed pesticide applicator usually found through a tree service. I chose the biological control. There is one predator of HWA that has been approved by the federal government for release in the United States. It is a Japanese lady beetle called S. tsugae, and it is a predator of HWA in Japan were HWA originated. The beetles can be got from Tree-Savers, a licensed vendor in Scranton PA, and are available through internet purchase, or by having Tree-Savers come to your property and give you and estimate. I recommend you get estimates for chemical and biological treatments and see what meets your needs. It takes around 100 beetles for a large tree and 50 for an infested smaller tree. If your infestation is just starting, you will probably stop it before it gets out of control. Right now the HWA is still in its woolly coat, and its eggs are hatching. The newborn nymphs called crawlers will head toward new growth and attach to the base of a needle. You can't see crawler without their wool, so you may not realize they are doing damage to your hemlocks.