use sevin and read the directions carefully.....wear old long old clothes, mask, goggles, gloves & hat.............keep children & pets away.............soak inside the roots............do the other dead tree anyway to kill whatever has killed it.............so this very early morning or very late when the sun has passed..............do this when there is no wind...............the directions will tell you how and when to spray again....you might be able to do it again in 2 weeks..........................if this treee survies.........do dormant oil to all your fruit trees in the fall....that smothers any eggs that has been layed in the bark and the hole in the bottom. same conditions are the one above.