Hello,

Canadian Hemlock (Tsuga canadensis) has many problems including elongate hemlock scale, spruce sider mite and cryptomeria scale which may cause yellowing of needles, premature needle drop and eventual branch and limb dieback. Read more here:

https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?taxonid=285010

And here: https://extension.psu.edu/spruce-spider-mite

https://extension.psu.edu/elongate-hemlock-scale

You also may have heard of wooly adelgid which is an invasive insect that attacks hemlock.

https://www.michigan.gov/invasives/0,5664,7-324-68002_71241-367635--,00.html

There are also environmental factors that may affect the tree. Planting the trees too deep, could lead to increased stress. Often, when trees are transplanted to different soil than what they were used to at the nursery, they can suffer from transplant shock. Too much water or too little water can lead to transplant shock also. When a tree is stressed, it is susceptible to insect attack.

It is difficult to analyze the trees’ problems by the photographs. You can send photos to MSU Extension’s Plant and Pest Diagnostic Lab for a more thorough analysis. Go to https://www.canr.msu.edu/pestid/ to learn how to send the photos and samples.

You can also consult a certified arborist at www.treesaregood.org, the website of the International Society of Arboriculture to find a certified arborist near you.

Thank you for contacting Ask Extension.