Hi DW,
Don't fret about not knowing. I've been gardening for years, 16 of which have been serious, and I learn something new all the time! :) Besides, folks not knowing the answers to everything keeps these forums going.
One rule of gardening is NOT to fertilize a stressed plant or tree. Support is what is needed and usually that can be done with organic measures like compost and compost tea. Take a look here for sick tree treatment and do what you can. It shouldn't need any more water than the others next to it.
http://www.dirtdoctor.com/view_question.php?id=130
What I did read is that you have ants. If the ants are on the tree then that indicates another problem of what is going on. It's probably not the ants that are the problem, but what they are after, unless you see them going from the tree to your house. If that's the case, you may have carpenter ants. I had the same problem with an old cherry tree. The ants marched off the tree and into my rafters! Ants harvest honeydew from aphids. It's what comes out the back end of the aphid after it happily sucks the goodness out of your tree. There are different types of aphids and you will need to id which you have from that site I gave you. If you can't seem to find them, then it's not the wooly ones as they are easier to spot. If you get rid of the aphids, which are what will hurt the tree, then the ants will go elsewhere for food. Isn't mother nature interesting? :o
http://www.ext.vt.edu/departments/en.../carpants.html
Look for pine bark adelgids or pine aphids. I DO NOT RECOMMEND the toxic stuff at that site I gave you last time,
http://www.uky.edu/Agriculture/Entom...rees/ef412.htm
but instead try one of these environmentally solutions based on what you find. You can use one of these that have oil in them if horticultural oil is recommended.
http://www.dirtdoctor.com/view_question.php?id=6
I'm going to visit my daughter this evening and won't be back until Sunday afternoon. So if I don't respond to any more questions until then you will know why. Don't hesitate to ask more questions if this isn't clear to you or you observe something else going on.
Newt
When weeding, the best way to make sure you are removing a weed and not a valuable plant is to pull on it. If it comes out of the ground easily, it is a valuable plant.