As Spring unfurls the leaves and blossoms of your apple and pear trees, check your trees for Fire Blight. Fire Blight is a very destructive bacterial disease of apples and pears. The disease is caused by the bacterium Erwinia amylovora, which will infect and can cause severe damage to many plants in the rose family of which apples and pears are members.

The bacteria usually enter the flowers through natural openings such as stomates. Aphids, leafhoppers, lygus bugs, and other insects with piercing mouthparts may transfer fire blight bacteria directly into susceptible tissues. Wounds to the tree from hail or other severe weather, can lead to a severe outbreak of fire blight. Any fresh wound can serve as an entry point.

While for many trees, bees and other insects alighting on blossoms is good news, they are part of the problem with fire blight as bees and insects will help the spread of the disease. Rains and temperatures about 65 degrees in the spring will bring the disease which has overwintered in cankers on the tree trunk and branches, to the surface. Bacterial ooze appears in the new infections on growing shoots which then continue to infect. In early to midsummer, during prolonged periods of muggy weather, blighted shoots and spurs, infected fruit, and new branch cankers all may have droplets of ooze on them.

Signs of Fire Blight:

  • The blossoms, twigs and branches will turn dark brown to black

  • The blossoms will look like they have been burned by fire.

  • Two main symptoms are shoot blight and cankers on limbs.

  • The blighted blossoms and leaves stay on the tree.

  • If the fruit is breached, the bacteria may also invade fruit, which becomes water soaked. Droplets of bacterial ooze appear on the surface. The fruit becomes leathery, turns brown (apples) and black (pears and quince), shrivels, and usually remains attached to the fruit spur.

Trees are most susceptible to this potentially devastating disease if a freeze occurs after blooming. While this does not happen every spring in New Jersey, it happens often enough to be a concern. This year frost warnings extended into late May.

There is no cure for fire blight. The remedies for fire blight are the removal of any infected stems or branches by pruning. If the tree is damaged to much, it will need to be removed.

The good news is that it is not spread through the soil, so trees can be replanted in the same area.

The bad news is twofold:

  • A warm, rainy, and windy spring helps spread the bacterium as does the pruning tools used to remove branches.
  • Even if you pruned your trees last year, you will need to do it again this year. The bacterium can survive the winter in sunken cankers on infected branches. In spring, the bacteria ooze out of the cankers and attract bees and other insects. Insects also help spread the disease from affected trees to healthy trees.

If the disease overwinters in your trees, this year will not be better. Having the professionals at Precision Tree and Landscaping out to assess your trees at the first sign of fire blight is the best way of saving them.

Some of the more affected trees types:

  • Callery pear, a popular landscape tree.

  • Apple types most affected are Braeburn, Fuji, Gala, Granny Smith, Jonathan, Rome, Yellow Transparent, and Idared.

  • Quince

  • Asian pears and red pear varieties.

Controlling sucking insects like aphids and leaf hoppers, is a good way to fight fire blight during the summer. Applying streptomycin sprays within 24 hours after hail or a storm with severe winds to prevent new infections is a good practice. Calling Precision Tree and Landscaping is the best practice as they can also help pick out fire blight resistant fruit and ornamental trees.