Answer: Hemlock (Tsuga) can exhibit browning foliage if subjected to drought, planted in poorly draining soils, or when insects or diseases are present. It's difficult to diagnose a problem without seeing it. Carefully inspect the browing foliage for presence of insect pests (look for webbing from spider mites, cottony tufts from adelgids or scale insects) and look for fungal spores (black or rust colored spots). If you find anything at all on the affected foliage you'll know insects or diseases are at fault. If the foliage doesn't contain any insect or disease, the problem is most likely environmental - perhaps drought stress or standing water.
Hope this information helps you determine why your hemlocks are turning brown.
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