Fire blight is a bacterial disease of apples and pears that destroys blossoms, shoots, and limbs, and sometimes kills whole trees. In general, apple trees are susceptible to a variety of disease and insect problems and require a spray schedule to manage them. The best recommendation is to select disease resistant varieties. See our website for photos and more information. https://extension.umd.edu/hgic/fireblight-trees
To manage fire blight, we have recommendations for pruning (called "ugly stub pruning" during dry weather) and the spray schedule on our website from Virginia Tech.