Fire blight wreaks havoc on pear tree
Question: We have a pear tree in our backyard that has produced fruit for many years. However, starting last year and again this year, some of the branches at the top of the tree have turned black and look wilted at their ends. Last year we cut these black shoots off, but I’m not sure if we made it worse because there seems to be more of them this year. Do you know what’s going on with our pear tree and if there’s anything we can do to stop it?
Answer: From your description, it sounds like your pear tree has developed a case of fire blight. For confirmation, you can send a tissue sample to the Penn State Plant Disease Clinic .
The fire blight pathogen (Erwinia amylovora) affects all pome fruits, including pear, quince, apple, and crabapple. It also affects some ornamental plant species, including Pyracantha, hawthorn (Crataegus), spireas (Spiraea), serviceberries (Amelanchier), mountain ash (Sorbus), and several others.
Unfortunately, as you’ve discovered, fire blight is a very destructive bacterial disease that can destroy branches, fruit and flower clusters, limbs, and even entire plants. Early signs of a fire blight infection include a watery ooze that weeps from small cankers of dead tissue from the previous season. But, often the disease isn’t noticed until entire plant shoots, flower clusters, and fruits begin to shrivel and turn black or brown, making it look as if they’ve been burned by fire. Blighted shoot tips often bend over at their tops, forming a “shepard’s crook” shape.
The bacteria is spread from one plant part to another by rain and/or insects. Injuries are common entry sites for this pathogen; hail damage can be a precedent to disease development. The disease is also readily spread via pruning equipment. Because of this, it’s very important that you disinfect all pruners, loppers, and saws with a 10 percent bleach solution or a spray disinfectant between each and every pruning cut, especially when moving to an uninfected tree. You should also only prune in dry weather.
Succulent new growth is particularly vulnerable to fire blight infection, so do not over-fertilize or over-prune susceptible plants. Also, monitor plants regularly and cut out and dispose of any infected branches during the dormant season. Do not cut off the diseased shoots now; wait until the winter. To cut out infected branches, follow the infected branch all the way from its tip down to the point where it connects with another branch, then cut out the blighted branch and the branch it’s connected to. Dispose of the infected branches by throwing them into the garbage or burning them.
When it comes to managing fire blight and other plant diseases, prevention is key. For future plantings, be sure to choose fire blight-resistant varieties whenever possible.
As for product controls that help manage fire blight, copper-based fungicides are useful, but pruning out the infected branches in the winter is a far more effective method for managing this disease.
Horticulturist Jessica Walliser co-hosts “The Organic Gardeners” at 7 a.m. Sundays on KDKA Radio with Doug Oster. She is the author of several gardening books, including “Attracting Beneficial Bugs to Your Garden: A Natural Approach to Pest Control” and “Good Bug, Bad Bug.” Her website is jessicawalliser.com.
Send your gardening or landscaping questions to email@example.com or The Good Earth, 622 Cabin Hill Drive, Greensburg, PA 15601.