Pests and Diseases: Fire Blight

After a week talking about our Lunatic Tour at Polyface Farms, it’s time to get back to gardening. While I believe that we can learn a lot about gardening from Polyface Farms, I know that you have questions about the plants that you are growing in your backyard. If you have Bradford Pears in your yard, you may be experiencing symptoms that look like this:

fire blight

This picture shows the classic case of fire blight. Fire blight is a bacterial disease that affects Bradford pear trees as well as fruit-producing pears. Its victims can also include apples, crabapples, Pyracantha and hawthornes. Fire blight gets its name from the damage that it causes: it looks like someone has gone around and set the tips of your plants on fire. The leaves turn brown and then black and the affected areas can reach a foot or more from the terminal growth tips. This damage causes a classic shepherd’s hook appearance. Fire blight can also affect the blossoms and they end up turning brown prematurely and dying. Let’s take a closer look at the life cycle of fire blight in order to understand it better.

The bacteria that causes fire blight causes cankers that generally set up shop on the trunks of the trees. These cankers weep and ooze and allow for the bacteria to be transmitted from tree to tree by insects as well as wind driven rain. Sooty mold is often seen growing near the cankers due to their sweet exudate. With the mild winter and wet spring that the Mid-Atlantic Gardening region is experiencing, fire blight infections are a common experience in a landscape still dominated by Bradford Pears. It’s one more reason to remove Bradford Pears from your landscape…or at least vow not to plant anymore.

So what can you do if your trees are infected? If the outbreak is relatively minor, you can prune out the infected branches, ensuring that you remove an additional 8″-12″ of stem below the apparent infection. Dispose of these branches in a landfill or burn them if your local conditions permit it. You can also spray your trees with a bactericide every 7-10 days from bloom time through the spring rainy season but who wants to go through all of that trouble?

The old saying that “an ounce of prevention is worth a pound of cure” certainly applies here. There are many, many varieties of apples, pears and crabapples that are resistant to fire blight. While that doesn’t mean that these varieties will never get fire blight, it does mean that they stand a fighting chance without a lot of fussing over them by you. Resistant apple varieties include Honeycrisp, Jonagold and Winesap. Resistant pear varieties include Honeysweet, Magness and Moonglow. If crabapples are more your style, consider planting Candied Apple, Louisa or Prairie Fire. Consult your local extension agent for other varieties that work well in your gardening area.

If you have experience with combating fire blight in your landscape, please leave me a comment below or e-mail me at stacey@midatlanticgardening.com. If you enjoy being part of the Mid-Atlantic Gardening community, join our e-mail list, become a fan on Facebook and follow me at Twitter. Happy gardening!