Twig blight can cause some dieback in junipers.
Q: Two of the large junipers (Juniperus chinensis 'Sea Green') in my privacy screen are showing some dieback. The tips of several branches near the bottom and inside of the shrubs are brown, and I see no evidence of mites. What could be wrong?
A: Sounds like you may have a twig blight such as Phomopsis, especially if your spring has been wet or there has been overhead watering. Take a cutting into an extension agent to get the particular blight identified. When the foliage is dry, prune the dead tips, cutting a couple of inches into healthy tissue. Remove the prunings; don't compost or put in a brush pile. Protect new growth by applying mancozeb or similar fungicide every seven days until the new growth has matured. Follow package directions for dilution amounts.