[Guest blog post by Judy]
Hello, my fellow fruit-lovers!
It has been very cool and wet here this past spring and summer. Of course, these are ideal conditions for bacterial diseases to infect our fruit trees, as well as other trees and shrubs. Since bacterial diseases are so common among fruit trees, I thought you home growers might like some background on one of the most prevalent bacterial diseases affecting apple and pear trees – Fire Blight. I am also going to give you some ideas on how to fight this disease!
Fire Blight is a contagious, systemic, bacterial disease. Bacteria (erwinia amylovora) attack the blossoms and then move up the twigs and branches through the tree system. The name “Fire Blight” comes from the scorched appearance of the infected leaves, stems, and bark. These areas may appear black, shrunken, and cracked. Blossoms will turn brown, wilt, and die about 1-2 weeks after infection occurs.
Fire Blight may also exhibit an amber-colored ooze (which is heavy with bacteria) from the bark of the tree. When the temperature begins to climb between 60°-80°F, it brings the bacteria out of dormancy and creates optimal conditions for spreading the disease. Bees, insects, birds, splashing rain, and wind easily spread Fire Blight disease.
Fire Blight commonly affects apple and pear trees (both fruit-bearing and ornamental varieties), but can also affect quince trees and other members of the Rosaceae family (including most common rose varieties and raspberry plants).
But we donʼt want to turn this into a science lecture*, so letʼs move on to how to handle Fire Blight.
Cultural practices. Any excessive amount of new growth on your tree is easily susceptible to Fire Blight infection. To avoid this, we recommend feeding with a low-nitrogen fertilizer during the growing season (stopping before July) – and only when necessary.
Clean up. Be sure to do a complete clean-up around your trees when fall rolls around. Collect all pruning debris, any mummied fruit, and leaves. Move them away from the trees and destroy them (do not put in compost). This will prevent the bacteria from over-wintering in the debris and then spreading. Be sure to also remove any tree suckers; since they are fast-growing and tender, they will also be vulnerable to infection.
Because Fire Blight is highly contagious, take care to disinfect pruning tools. Sterilize the tools in a household bleach solution (ten parts water to one part bleach). Dip clippers between cuts. Be sure to wipe clippers dry to prevent corrosion. Alternatively, you can use alcohol wipes to clean your clippers between cuts, both protecting your trees and your tools.
Chemical control. A good Fire Blight Spray can help control infections and should be applied rom bloom time through the spring storm period, following the product label. Removing the blighted wood from infected shrubs and trees can help prevent the disease spreading. Prune off all infected branches at least 8 inches below the blighted area. Burn the affected branches, if possible.
There’s not one single practice that will insure complete control of Fire Blight. When we’re dealing with Fire Blight here at Stark Bro’s, we prune out the blighted areas immediately and do a thorough clean-up to prevent re-infection and minimize spreading. In high-pressure areas, your best defense is likely going to be a combination of cultural, chemical, and clean-up control methods. You may prefer to contact your local county extension experts to help you diagnose and control an outbreak of Fire Blight in your area.
I hope this information gives you a good understanding of Fire Blight and helps to make your fall, winter, and spring productive and disease-free!