What Is Wrong With My Tree? Fire Blight

Fire Blight Is A Bacterium

Fire blight is caused by a bacterium called Erwinia amylovora that affects the flowers, fruit, stems, and leaves of trees and shrubs. If not controlled, it can cause dieback and even kill the plant.

fire blightWhat Trees & Shrubs Are Affected By Fire Blight?

While fruit trees like apple and pear have problems with fire blight, trees and shrubs affected by the bacterium include:

  • Hawthorn
  • Crab apple
  • Mountain ash
  • Bradford pear and other pears

What Is The Lifecycle Of Fire Blight?

The fire blight bacteria overwinters in cankers in infected bark and spreads rapidly in warm, moist weather via rain, dew, wind, and insects. Cankers can be present on the twigs, branches, or trunks of infected trees. When the weather warms in spring, the cankers produce an ooze containing the bacteria that then spreads to new sites.

What Are The Symptoms Of Fire Blight?

Symptoms of fire blight include:

  • Overwintering cankers
  • Rootstock infections
  • Scorched appearance of leaves
  • Creamy white to amber colored ooze

What Are The Treatments For Fire Blight?

Since fire blight is considered seasonal, property owners should watch for rapid browning of new leaves is spring and blackened or scorched looking twigs. The browning can be rapid enough to kill a tree in one season, but it more commonly takes two to three years for a tree to die from an infection.

With that in mind, as soon as fire blight is discovered, infected branches should be removed and destroyed. Pruning is best left to arborists as the placement of the pruning cuts is a critical step. Poorly placed cuts will actually hasten the spread of the blight.  While there are treatments that include injection of antibiotics (yes, even for trees!) the applications need to occur prior to the reoccurrence of spring symptoms. New plantings should include blight resistant species and cultivars.

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