Question
Hi jennifer,
We are in central Maine, and have many long needled pine trees(probably eastern white pine)...one that we transplanted many years ago, that has thrived, is now not looking so good. Many of the needles are turning yellow and brown on the lower branches,and it looks like small amounts of white sudsy stuff have appeared on some of the branches. There are some greyish patches here and there on the bark (but lots of other trees in the yard have that too).
What do you think?

Answer
Gale,

The grayish patches on the bark may be lichens which are perfectly normal.  As for the white sudsy stuff, it sounds like an insect problem.  My best guesses are adelgids or scale insects.  You will have to look at a few pictures and then take a closer look at your trees to figure out which you might have.

This fact sheet will show you images of pine needle scale and gives management recommendation.  It also mentions natural enemies/predators that may be helping you with the problem.  Take a look and see if you have scale insects.
http://www.migarden.msu.edu/uploads/files/8/e2812.pdf

The adelgids that get on pine can be on the needles/twigs or on the trunk.  Sometimes they look frothy, so this may be what you are seeing.  Here are a few images and information about the problem.
http://www.extension.umn.edu/yardandgarden/yglnews/ygln-may1500.html
http://bugs.osu.edu/bugdoc/Shetlar/factsheet/christmasstree/pine_bark_adelgid.ht

I hope this helps you solve your problem.  It is difficult for me to know exactly what is going on without an image of the problem.  But, these are likely causes based on your description.

Good luck with your plants.
--Jen