Fire blight often devastates pears and apples in spring, but it does not damage peaches. It is more likely that peach tree borers are killing your trees. These are the larvae of a small, clear-winged moth that lays eggs in bark crevices in spring. The trees are damaged or killed when the eggs hatch and the larvae bore holes into the wood. Young trees with a slender trunk are often killed. Check your declining trees for evidence of borers: 1-16-inch-diameter holes that may have a gooey substance oozing out. The holes are evidence of borers. You may be able to kill the borers in the holes by inserting a wire into the hole to skewer the wormlike larva. Prevent future borers by avoiding injury to the bark; borers seek out injured trees. Purchase pheromone traps to hang in your trees in spring to early summer, when the adult borers take to the air. These may trap them before they reproduce, and they serve as an indicator of when to apply insecticide. Spray the trunk and base of the tree with an insecticide labeled for peach tree borer. Poor drainage also shortens the life span of peaches. They develop root rots.