The use of resistant varieties is the first line of defense. Listed on the table below are apple and crabapple trees with certain degrees of resistance to the blight. Resistance doesn't necessarily mean immunity. A tree with resistance can become infected, but the problem won't be nearly as severe as if there were no degree of resistance. Avoid overfertilization with nitrogen.
Nitrogen stimulates new growth and the new growth is highly susceptible to fire blight infection.
Practice sanitation when pruning trees. Prune out and destroy all infected and dead plant tissue. Make pruning cuts 6 to 12 inches into healthy tissue. Always dip tools in a disinfectant solution, such as 10 percent household bleach, between each cut to minimize disease spread. Prune newly infected twigs as soon as possible in the spring.