Cypress tip moth or leaf miners are the most destructive of the insects. Look for holes in the needles, or tiny silk cocoons in the crotch of needles or twigs. These insects can build up until the entire plant appears to be brown. Fortunately the branches remain alive and once the leafminers are controlled the tree will green up again. Pesticide timing is critical.
Spider mites can build up to damaging numbers.
Close examination of off-color foliage with a handlens will reveal irregular brownish rasped areas on the leaf, revealing mites, mite eggs, or webbing. Mites are usually more of a problem in hot dry climates or seasons. Pesticides don t work against eggs so a second or third application is sometimes needed. Use enough pressure to penetrate dense foliage. It is a wonder junipers survive as well as they do considering this rather formidable list of problems.