This is the time of year when the oldest needles of evergreens turn yellow or brown and fall from the tree. This normal senescence is often mistaken for a disease problem.
Environmental stresses can influence the timing of needle drop.
Seasonal needle drop is usually most noticeable on white pine and arborvitae. Prepared by Paula Flynn , Department of Plant Pathology Iowa State University , Ames, Iowa. This information subject to a usage policy .