- Author: Dustin Blakey
All over our region we are receiving reports of fire blight occurring on fruit trees. This bacterial disease primarily infects pears, apples, quince and pyracanthas in our area. While there are a few other species out there that can be affected, it is unusual to see them attacked. Peaches, plums and cherries are not affected by this disease.
Fire blight is a bacterial disease. It usually gets its start during the bloom period of susceptible hosts. Early on it looks like wilted shoots and flower buds. Most gardeners do not notice the disease until it has turned entire shoots black. This burnt appearance happens suddenly which gives the disease its name.
By the time you see burnt shoots, it is too late to do anything to stop it. You're too late now. This summer, plan on pruning out all diseased wood. If you miss any, remove the remainder this winter. Removal of diseased material is important in controlling the disease in the future. The disease is primarily spread through flies and bees interested in the flowers. By removing sources of infection via pruning, your chances of getting the disease diminish. Sometimes this means pruning out a lot of the tree.
Disease growth is favored by a certain range of temperatures that occur in spring. In our area this coincides with turning on irrigation which raises humidity. Late spring storms, even if they don't bring rain, do often raise humidity as well.
There isn't really an effective spray option available to homeowners. Even farmers have a hard time with sprays of this disease. The UC IPM program has a brief summary of spray options at the end of this informative fact sheet. If you do spray, this occurs during the infection season as a means to prevent the disease. After-the-fact sprays have no effect. Don't bother trying.
There are great differences in susceptibility to fire blight by cultivar (variety). If you find that your pear or apple is always being afflicted with fire blight, consider replacing it with a more-resistant cultivar. Usually catalogs point this out.