It's the larvae (called a grub) of one of the scarab beetles....like a Chafer beetle or June beetle or even Japanese Beetle. What kind of beetle do you find messing around with your fruit trees in the spring or summer?

im not sure/ one of the main problems i have is that starting in the summer, the tops of all my fruit tree shoots wilt and further down the stem, the wood looks like it has been necrotized/decayed. does that sound like damage from any of these beetles?

Short answer: No.

The beetles I mentioned would normally be foliage and/or fruit eaters. Very noticable in their adult stage. In some species, the larval stage can cause damage to tender roots (especially for seedlings and lawns), not in regards to your fruit trees, I'd think that you would have noticed some adult beetles.

Where are you located, in a general sense?

brooklyn NY

Anyone have any idea what might be attacking my fruit trees based on the description i gave.?

There are predatory nematodes you can purchase that will help with control of these pests. Application is said to be best in August or early September.

Birds and skunks like to eat them.

Sue

lycheeluva, (twig)borers and girdlers are the intermediate stage of some beetles that attack trees near the growing tips. One of these may explain the necrosis you have observed and it may account for the wilt/death of the twig beyond this point.
On the other hand, you may be seeing the damage caused by separate organisms at the two sites but is unlikely, in my opinion. As far as I am aware, healthy trees recover. Certainly that is the case with the black twig borer, Xylosandrus compactus, in my experience.