Pine needle drop happens every year. Some years it is more obvious or dramatic than others, but some needle loss occurs every year. Deciduous trees' leaves change color, and all drop pretty much at the same time. White pine (Pinus strobus) drops its third-year needles. The 1- and 2-year-old needles remain on the tree, making it "evergreen." If the tree put on a great deal of growth 3 years ago, and produced a lot of needles, the leaf drop will be more noticeable this year. This is a natural occurrence and not something to be alarmed about. Other evergreens also have seasonal needle drop, but it's usually most apparent on white pine.