On Evergreens Evergreens are sometimes injured by chemicals. The main sources of injury are salt, herbicides, and swimming pool chemicals.
Salt can come from two sources.
The first, and most common, source is road salt. The spray kicked up by passing cars will blow to nearby evergreens. If the injury is slight the plant may just yellow. If the injury is severe the needles may be killed and the branch may not grow. Road salt can be in run-off from roads and, to a lesser extent, sidewalks.