Fire Blight In Pear Trees

"Fire Blight" is a common problem in members of the Rosa family including pears, apples, and flowering quince.  Generally, we see most of our cases of fire blight in pears, including the ornamental Bradford pear.  In very wet years,  we see fire blight in apples, photina, quince, pyracantha, etc.  The blight is not usually persistent, but the pear seems to be the most susceptible host.

    The reason this disease is called "fire blight" is because the new growth tips of the plant look as though someone has attacked them with a torch.  The blossoms turn black and die, followed by a dark blackening of the stem tips which quickly moves down the twig into the upper branches.  This is a rapidly spreading bacterial infection (Erwina amylovora) which damages mature trees and often kills young trees.  Once the disease begins,  there is very little you can do to stop its spread during its growth season.  A fungicide containing Streptomycin sulfate or "Fire Blight Spray" must be applied from the point of bloom through the emergence of the new leaves.  This would require 3 sprayings,  about one week apart.  In the event that you would miss these sprayings, later treatment will probably not render any significant results.

    Most diseases thrive in warm, wet conditions,  with Fire Blight being no exception.  Diseases enter the plant through the plant tissue.  The more tender the shoot, the easier the entry.  This is why a healthy, well established plant is more resistant to diseases than plants which are stressed or have a flush of soft new growth. The new growth can be more easily penetrated by the bacteria or spore.  For this reason, you should not apply nitrogen to pears in the spring.  Nitrogen will promote new and tender growth, thus promoting the Fire Blight.

    If your tree is affected with Fire Blight, you must allow the disease to run its course.  Later in the summer, after the spread has stopped, you may carefully prune out the infected branches.  This is accomplished by cutting the branch 6 to 12 inches below the affected area.  Be careful not to touch the diseased branch against healthy branches when removing the cuttings.  Between each cut dip your pruning shears in a cup of rubbing alcohol or Clorox to sterilize the shears so you do not further spread the bacteria.  In the case of a small tree, you may not have much left after this procedure.  Sometimes you just have to wait until March to start your Streptomycin sulfate therapy.

    Diseases exist in nature.  Sometimes you have them, sometimes you don't.  Using proper cultural habits and fertilization schedules will help you avoid an encounter with these opportunistic little rascals. Don't be discouraged, just garden smart!