Tom Creswell, Director, Plant and Pest Diagnostic Lab
Fire blight is one the most common and damaging diseases we see on apple trees, pear trees and ornamental pear trees. The bacterium that causes this disease (Erwinia amylovora) survives the winter in cankers on tree branches and is spread by insects, wind and rain to cause new infections in flowers and wounds during spring growth. Pruning out fire blight infected wood is the most important control measure but it must be done correctly and at the right time to be effective. Late winter is a good time to prune out fire blight cankers before new growth begins.
Here are some guidelines: