Controlling Fire Blight

A disease called fire blight has been widespread on susceptible varieties of apples and pears in home orchards this spring. In the landscape and ornamental trees such as Bradford pears as well as ornamental shrubs like flowering crabapple, hawthorn, roses, flowering quince, and pyracantha are also affected.

Fire blight usually shows up about this time of year in our area, however it’s been more common this season because of wet conditions and cooler temperatures over the past few weeks. This is a bacterial disease, it shows up on the tips of the branches of diseased trees and they have a “scorched” appearance like they were burned. Hence, we have the name “Fire Blight.”  Also, tips of infected branches are curved like a shepard's crook.

 In some cases, branch dieback is so severe that many homeowners become concerned about the survival of the tree. Death of a tree or shrub from fire blight is not common, but can occur from damage building up over several seasons.

 Unfortunately, for the homeowner with fire blight problems, there are few control procedures that can be carried out at this time of the season. Some control has been reported using a streptomycin antibiotic solution during the bloom time which prevents the bacteria from entering the branches through the flowers. However, at this late in the season, about the only control is pruning of diseased branches, and it is not recommend at this time of year unless fire blight damage is severe.
 

First, do not prune during rainy weather; second, all cuts must be made several inches below the point of visible infection. Third, pruning tools must be disinfected with each cut, and you may use a 10% household bleach solution by mixing 9 parts water to one part bleach. Make sure to rinse, dry and oil the pruners after use, because bleach is corrosive.

Other practices used in conjunction with pruning are to prevent cankers on large limbs and trunks by rubbing off water sprouts during the spring and summer. Also, avoid heavy nitrogen fertilization at any time during the season because it promotes succulent new growth that is susceptible to fire blight infection.