Have You Checked Your Hemlocks Lately?

If not, you'd better get out in the yard and do so. Hemlock Wooly Adelgid is now pervasive in Concord and the Greater Boston area. The Carolina Hemlock (Tsuga caroliniana), was first found to be infested in Georgia in 1951. Since then, it has spread up into New England and is devastating Eastern Hemlocks (Tsuga canadensis), from Connecticut into Massachusetts, Rhode Island, Maine, New Hampshire and Vermont. 

Woolly Adelgid is native to Asia where its natural predators keep it in balance similar to other indigenous Adelgids in the US. Here, however, Wooly Adelgid has no predators and has killed thousands of acres of Hemlocks from Georgia well into New England. Once infested and untreated, the Hemlock will die, usually between 3-6 years and often less. In Massachusetts, it is likely that many of our wild Hemlock stands, now infested, will perish in the next 10 years or so. This winter while snowshoeing behind my house in West Concord I noticed that the wild Hemlocks were all infested. Having no protection, they will surely perish. That makes those of us with Hemlocks on our properties stewards to protect one of the most beautiful native New England trees we have. In this writers opinion, there is nothing like the beauty of a full, dark green Hemlock.

Adelgid propagate during the warm season and feed on the Hemlocks during the colder winter months.  One Adelgid can turn itself into 90,000 during the seven warm months. Birds are the biggest vector and drop Adelgid from tree to tree all year long. 

What can you do? Great question! The first thing is to check your Hemlocks regularly or have your local Arborist do an evaluation for you. If your Hemlocks are Adelgid positive (see picture), you should have them sprayed with horticultural oil at least once a year. For really tall or hard to access Hemlocks, you would have them treated systemically with imidacloprid. DO NOT spray your Hemlock with Oil from mid May through late September as you will risk burning the plant in hot weather and suffocating the new growth. You can use an insecticidal soap anytime during the warm season. Fall is the best time of year to spray as the Adelgid do most of their feeding (sap suckers) during the colder winter months. If your Hemlocks are infested, fertilizing them with a low-nitrogen fertilizer during the spring and fall will help them bounce back nicely.

Questions? Write me at whitefalcon2@gmail.com.