Answer: There are a number of things that can cause browning on Junipers. The most common are over-fertilization, inadequate water (or too much water and poorly draining soils), winter freeze damage, spider mite infestation or herbicide damage. I think we can rule out some of the above causes and concentrate on those that are more likely; Using herbicides around established plants is risky business. Some, such as Round-Up, can be translocated to the roots, which may affect the roots of your junipers. Freeze damage will show up on the tips of the branches (you didn't specify where the damage is showing up), and spider mite damage typically occurs in the center of the plant. Spider mites cause webbing where the stems meet so check carefully. You might even try holding a sheet of white paper near the center of your juniper and sharply striking a branch or the trunk. Spider mites will be dislodged; they look like specks of pepper, except that they move.
If this information still doesn't shed any light on the problem with your junipers you might want to take a sample of the problem to your local Cooperative Extension for microscopic evaluation. Best wishes with your junipers!
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