Fire blight is a bacterial disease that can kill branches and whole plants of many members of the rose family, including apple, pear, quince and crabapple. .
Symptoms include dead branches, water-soaked blossoms, light brown to blackened leaves, discolored bark, black “shepherd’s crook” twigs, and dried fruits. .
Fire blight bacteria can be spread by insects, splashing rain or contaminated pruning tools..
Management includes resistant varieties, cultural practices, pruning and preventive chemical sprays.
Read more about Fire Blight here, and why it's important to prune these trees during the dormant winter season: http://extension.colostate.edu/topic-areas/yard-garden/fire-blight-2-907/