Answer: It is normal for the oldest, innermost foliage to turn yellow and die, but it might also indicate a spidermite problem. When spidermites feed they suck the fluids out of the foliage and make it prematurely yellow and fall. To check for spidermites, inspect the branches towards the inner part of the plant and look for webbing. Or, take a piece of white paper, hold it in among the branches and sharply tap the branch. Some debris should fall onto the paper. If tiny specks start to move, they are likely spidermites. These pests like dry, dusty environments so regularly hosing off your thujas, directing the water towards the center of the plant will discourage these pests. Good luck with your plants!
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