Its not an infection, therefore your other fruit trees will not be affected by this tree.
What you are describing is a tree that is being eaten by critters at its root system. Not insects, but probably moles or rodents. The tree does not have the ability to nourish all of its branches due to the problem. Unfortunately, there is no easy solution. The tree is probably dead or close to death, and should be removed, but the problem will remain and what ever has eaten its roots may move on to the next tree. If you decide to cut the tree down, you may want to get pest control to deal with the issues before they bloom out of site. Sorry about the loss of the tree. -Birdy