The needles on pine trees turn brown for a variety of reasons, most often including root death or damage, dehydration, fungal diseases and bark beetle infestation. Unfortunately there is little in the way of remedy where dead roots or bark beetles are concerned. On the positive side, there are treatments for common pine tree fungal diseases as well as procedures to help reverse some root damage and dehydration.
Pine trees with pitch flowing in large quantities from the trunk, holes in the bark and small piles of sawdust surrounding the base are likely under attack by bark beetles. These insects tend to target older or distressed trees. They may have damaged a tree beyond repair without it being obvious to the human eye, as a dead pine tree can remain green for some time before abruptly turning brown.
The most common cause of root damage is a result of freezing. Symptoms include flecks of brown appearing on the tree's needles and dieback, which is when new needles begin to die from their tips backwards. All species of pine trees are susceptible to temperature-related root damage, but young trees are particularly vulnerable to the condition.
Tree experts recommend planting pines in soil with excellent drainage, as well as watering the trees in the fall.