Answer: Arborvitae are subject to several diseases and some insects which could cause browing. Physical injury to the branches and other events such as accidental herbicide drift or root damage can also cause browning. Unfortunately, based on your description it is impossible to make a diagnosis of the problem. You might want to consult with your local county extension (431-7260) or a professionally trained and certified arborist for a diagnosis and suggested remedies. I'm sorry I can't be more helpful.
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