FIRE BLIGHT

MOUNTAIN ASH STRUCK BY FIRE BLIGHT...

...LEAVES AND BRANCHES LOOK AS TOUGH THEY WERE SCORCHED BY A FLASH FIRE...

...YOUNG BARK IS SHRIVELED AND SUNKEN...

...OFTEN, ONLY SOME  BRANCHES ARE AFFECTED...

...BUT THE VISUAL SYMPTOMS ARE THE SAME...

...OOZING BACTERIA ON INFECTED BRANCH  IN SPRING (Google photo)

Saturday, 8:00 AM.  65 degrees F at the ferry dock, 58 on the back porch.  Wind variable and calm.  The sky is clear except for  a few puffy white clouds.The humidity is 84% and the barometer has begun a gradual decline, now at 30.05".  It is a gorgeous, quiet morning and the weather should be good until Tuesday, when the chance of thunderstorms is predicted.

   Fire blight, Erwinia amylavora, is a serious and often fatal bacterial disease of plants in the Rose Family.  We see it mostly on apples, pears, quince and mountain ash.  The disease spores are spread by wind, rain, insects,  animals and pruning tools.  Spores gain entry through wounds in plant tissue and other means, and the disease is most prevalent in wet, humid spring and summer weather, when the daytime temperatures are between 75 and 85 degrees F and night temperatures above 55 degrees.  Trees that are growing rapidly are most susceptible, and over fertilization with nitrogen should be avoided.

   Orchardists are challenged by this disease and it is difficult to control even with commercial sprays and careful cleanliness.  For the homeowner the best prevention is promotion of good tree health and watching for the disease symptoms. The disease over-winters  in infected tissue, and first appears as a brown ooze on diseased tissue in spring.   Early detection of fire blight should be followed by aggressively pruning out affected branches, cutting well below the infected areas. At times the disease is so aggressive that a whole tree looks like it has been scorched by fire overnight.
  Since pruning tools can spread the disease, shears and saws need to be sterilized with alcohol or bleach after each cut.  Pruned leaves and branches should be burned or buried to prevent spread of the disease.  When purchasing new trees look for varieties that have proven resistance to fire blight.  About the only preventive spray available for home use is a weak Bordeaux mixture applied at blossom opening.