The Cornell Cooperative Extension has this word on what's happening with crab apples this season:
"Fireblight seems to be prevalent in our area this year. If you haven’t had problems in the past your crab-apple will probably recover next year. In the meantime collect fallen leaves and discard. Prune affected parts. Disinfect pruning tools between cuts with a 1:10 bleach to water rinse."
. . . submitted by Glynne Schultz