dying/diseased hemlocks
 

I have a 150 ft wall of 20 ft high hemlocks that act as a fence and privacy buffer between myself and the neighbors yard. In certain areas we have had trees die and others get very thin. A few years back we had a tree company come out and they treated for wooly adelgid. Did not seem to help much but hard to judge as who knows what it would look like with no treatment. I do think adelgid are present as from what I read they are everywhere in this area. Very expensive to treat and neighbor and I are thinking of doing it ourselves. Would also like to do something for tree health but the line runs to lake so we will not use anything that may cause harm. Any suggestions on products, methods, best time of year.... I did find a place that sells a type of Beatle that feeds on these things. That seems interesting.
https://www.treesaverspa.com

Hi, I read your post to my husband, a retired treeman, and he said dormant oil sprayed in the spring time would be his choice. It doesn't affect the lake unless you are spraying trees on the water's edge, because it is oil.

His company used Cornell's Ag school for help in different areas sometimes.

You could also look up how to make your own home remedy for certain trees, but as he says, everything gets something.

Good luck~

White Pines--Best for The Lake...
 

Beetles would probably work locally, but would likely need to be applied to each tree every spring.

In anticipation that your row of Hemlocks eventually succumb to WHA, I'd plant one White Pine sapling between each Hemlock. (Most understory woody trees are sun-crowded out by Hemlocks--including White Pines). After 15 years, you can select-out the weaker evergreen.

White Pines are fast growers, and a next-door neighbor who's planted hundreds has a huge privacy fence since 2006! Nobody's going to drive on their property...:rolleye2:

You'll remember the former airport on Wolfeboro Neck--check it out. ;)

If you had the adegid you need to spray each year. To many infected other trees nearby.

You may not be able to save the hemlocks.
If you already know what the Woolly Adlegid infestation looks like.. then it may be that.
It could also be Elongate Scale.

Or may just be stress from alkaline soils... maybe lawn lime a bit too close... to just the heat; both those would stress the trees and be very hard on them over time.