Fruit trees and small fruits Gardening Plant diseases

Blackened Twigs Can Mean Fire Blight

Fire light blackening leaves on an apple tree.

By Larry Hodgson

Fire blight is a disease mostly commonly seen on trees and shrubs of the Rosaceae family: cherries, apples, hawthorns, plums, mountain ashes, roses, cotoneasters, raspberries, etc., but also lilacs and other trees and shrubs. It seems to come out of nowhere at various points during the growing season, although often shortly after flowering. The symptom is quite recognizable. Suddenly, the leaves of one or two branches turn black and curl down, as if scorched, but without dropping off. Any fruits present on those branches mummify. Often the leaves and fruit linger on the tree all winter.

In the second year, other branches are affected. The disease can spread quite rapidly, causing cankers, discharge and bark discoloration on larger branches and the rapid death of any twigs that are affected.

World distribution of fire blight (Erwinia amylovora). Ill.: W!B:, Wikimedia Commons

This disease is caused not by a fungus, the usual source of plant diseases, by a bacterium, namely Erwinia amylovora in the case of the form that attacks members of the Rosaceae (rose family). It’s is mainly carried to the tree by bees or other insects during pollination, then is spread by rain as it drips down the plant from the outer branches to the trunk.

Mountain ash suffering from fire blight.
Mountain ash suffering from fire blight. Photo: extension.umn.edu

In some cases (in mountain ashes and wild cherries, in particular), fire blight is linked to senescence (deterioration due to aging). In such cases, the tree affected is already in decline, then fire blight moves in and finishes it off. In such cases, there’s nothing to do other than to cut and burn the affected tree so that the disease doesn’t spread to other plants in the area.

Lilac fire blight on a lilac branch.
Lilac fire blight, which also affects not only lilacs, but also roses, forsythias and oaks, among others, is caused by a different bacterium, Pseudomonas syringae, but symptoms are similar. Photo: Jerzy Opioła, Wikimedia Commons

Sadly, though, fire blight doesn’t just attack aging specimens, but can also affect previously healthy trees and shrubs. This is commonly the case with fruit trees and it can cause them to produce less or even die well before their time.

You Can’t Always Save a Tree with Fire Blight

Apple tree with fire blight.
Apple tree with fire blight. Photo: Robert L. Anderson, USDA Forest Service, Bugwood.org, Wikimedia Commons

Actually eradicating fire blight is very difficult. Often, in spite of a lot of effort invested in trying to save a diseased tree, the disease progresses year after year. Sometimes a determined gardener only admits defeat when the last branch dies.

When a tree is diagnosed with fire blight, it’s often best to eliminate it right away, especially if it’s an “ornamental,” as it will quickly cease to play its primary role!

On the other hand, a fruit tree with the disease can sometimes produce good crops for several or even many years. You have to be the judge as to whether trying to keep a diseased tree alive any longer is worth the effort.

The Generally Recommended Treatment

Here’s what to do to treat a tree or shrub with fire blight.

Pruning shears pruning an apple tree.
It’s mainly by removing branches affected by fire blight that you can maintain some control of the disease. Photo: MaxPixel

In dry weather, shortly after you’ve noticed the infestation, prune off the affected twigs between 1 and 2 feet (30 and 60 cm) below the infected part and burn them. Sterilize the pruning shears between each cut with isopropyl alcohol (rubbing alcohol, surgical spirit). And cross your fingers!

Sometimes people try fungicide treatments, whether organic or not, after pruning the affected branches, but the disease is bacterial and not fungal, so you can’t expect fungicides to be very effective. There are indeed bactericides that can sometimes be effective (streptomycin, for example) and may be available to commercial orchardists, but as far as I know, none are accessible to home gardeners.

Choose Resistant Varieties

Logically, you could try to keep bees and other pollinators, the main propagators of fire blight, away from trees and shrubs while they’re in bloom, but then there would be no fruit. Not really what you want if you’re growing fruit trees! 

The best solution is therefore to plant, from the start, a variety known to be resistant to fire blight. This kind of information is actually quite widely available. Well, maybe not in garden centers that sell fruit trees (one has to wonder why they continue to offer so many varieties well known to be disease magnets!), but online or by contacting a specialty nursery. For example, you can find lists of apple and crabapple trees that are resistant to diseases (including fire blight) in the articles No-Spray Apples and 50 Different Disease-Resistant Crabapples.


Fire blight: this is not an easy disease to control. You’ll just have to do the best you can!

Larry Hodgson is one of Canada’s best-known garden communicators. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

7 comments on “Blackened Twigs Can Mean Fire Blight

  1. Good video, thanks.

  2. Photinia and native toyon, which used to be classified as a Photinia, are very susceptible. The disease may not be seen for years, and then suddenly flare up!

  3. Balsamfir

    Do you know if philadelphus aureus is on this list? I had been struggling with similar symptoms (only once it got big enough to bloom). In the end, last year I pruned it down to almost the ground in an imitation of written advice from Christopher Lloyd. I haven’t seen any die back yet since then and it has grown well. But not yet blooming again. And we’ve had a wet humid summer, so obviously not a fungal problem.

    • Yes, it’s subject to lilac fire blight. There is even a special strain of lilac fire blight specific to the genus Philadelphus.

      • Balsamfir

        Thank you. That problem has been mystifying me for years, but I had’t figured it out.

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