Fire Blight

From the University of Georgia:

Many folks have apple trees in their yard, and they are a great addition to any landscape. They have beautiful flowers in the spring, and then in the late summer, you can pick the apples or let them feed wildlife. One of the biggest diseases that people have on apple trees is fire blight. This disease can spread rapidly through your apple trees. This year I have seen more of it around than normal. So let’s talk about fire blight and what you can do to prevent it from taking over your trees.

Fire blight is a bacterial disease, which separates it from many of the other diseases that we see which are fungal. The scientific name of the bacteria that causes fire blight is Erwinia amylovora. You will see the effects of it on blossoms, leaves, shoots, branches, fruits, and roots. It can affect other plants in the rose family. This includes pears, plums, cherries, and spirea among others. These plants are not as common, so they don’t get as much attention. A unique example is Bradford pears. They have some natural resistance, but they still can get fire blight.

Fire blight will normally enter the tree during bloom through the blossoms. Once it gets into the current season’s growth, it will move into older growth. Some of the symptoms that you’ll see are blighted twigs that have become water-soaked. Young twigs, branches, and leaves will die at the end and look like they have been burned. The branches may bend at the end forming a shepherd’s crook. The dead leaves remain on the branches.

Once an apple tree is infected with fire blight, it will spread throughout the tree. It is spread from infected trees to healthy trees by rain, wind, or contaminated pruning tools. It can overwinter in the tree and cause an ooze out of cankers in the spring. That ooze will attract insects that carry the fire blight to other trees.

If left untreated fire blight will kill an apple tree. So what can you do about it? The first step is to prune out infected growth during the spring and summer. Cut the infected branches out 8 inches below where the damage is. Dip your pruning tools in a 10% bleach solution between each cut to avoid spreading the pathogen. It is also important to spray your apple trees every 7-10 days with either copper hydroxide or streptomycin when leaves begin to emerge through bloom. Copper hydroxide can start to burn leaves as they get larger. Sprays are not 100% effective especially if you have a warm wet spring. Avoiding heavy nitrogen fertilization will help reduce infection during the summer.

Finally, plant apple varieties that have a natural resistance to fire blight to ease the challenge. A couple of varieties that have natural resistance are Arkansas Black, Golden Delicious, Liberty, Yates, and Winesap. A few varieties that are highly susceptible to fire blight are Fuji, Gala, Granny Smith, Pink Lady, and Empire.

If you have questions about fire blight contact your County Extension Office or email me at Jacob.Williams@uga.edu.