Fire blight is a disease caused by the bacterium Erwinia amylovora and can be highly destructive to flowering crab, mountain ash, chokecherry, and hawthorn. It can also affect some species of the rose family.
One symptom of fire blight is the death of the terminal shoots on the new growth in spring or early summer. The branches give the appearance of being burned or scorched by fire hence the name "fire blight". The shoots will turn black or brown as well as the new leaves drooping in a downward direction. Once the disease progresses down the branch it will position itself as a canker in the older parts of the tree or shrub. A good indication of these cankers is an orange colored material oozing from the diseased parts of the plant.
The bacterium over-winters in the large branches of the plant and oozes out from the cankers once spring arrives. Insects or wind and rain then carry these sticky droplets to other parts of the plant where it affects the new growth. Fire blight thrives under humid conditions but will also occur when temperatures hover around the 21 to 28 degree Celsius mark.
Currently there are no chemical controls the homeowner can use to control this devastating bacterial disease. The only way a homeowner can control the effects of fire blight is by pruning and then destroying the infected branches. This must be done in the spring to be most effective. Generally speaking a cut 18 inches below the infection or dead leaves is sufficient. The most important thing to remember when pruning out fire blight is that you MUST sterilize you pruning tools in rubbing alcohol after EACH CUT to prevent the spread of this disease to non infected parts of your plant.