Question
I noticed just today that the needles on the base of most of the branches of my 4 long needle pines have turned yellow.  I immagine they will fall off and the branches will then look sparse and the tree less full.  The trees are 15 years old and have never done this before.  One spruce planted close by also has some yellow needles on a few branches on just one side of the tree.  We had a fairly dry August but have had 2&/1/2 inches in Sept. Is this a disease?

Answer
It is probably not a disease.  Pines will drop needles twice a year, once in the spring and once in the fall.  It may be the previous dry weather is causing the tree to drop more than usual.  I would not worry too much about this situation.  Good Luck.