This is a bacterial disease that is a problem for trees in the Roseaceae family such as apple, crabapple, pear and mountain ash. The leaves and branches become blackened and look as though they have been burnt, and terminal branches bend over like a shepherd’s hook. Clear yellow liquid may ooze from infected branches. The disease can be spread by rain or wind, insects or by infected pruning tools.
There is no chemical control for Fireblight. Pruning infected wood may slow down the disease, but it may also create more problems if not done properly. Pruning tools must be disinfected after each cut with diluted bleach to remove all traces of the disease. All cuts should be made at least 10” (25 cm) into healthy wood. Copper or sulphur sprays may be used, but effectiveness is questionable.