Fire blight is the most feared disease of apples and pears, and its name is exact: a branch hit by fire blight looks as if it has been scorched by a flame. The blossoms brown and shrivel, the young leaves blacken and hang on the dead shoot, and the shoot tip bends over into a shape growers call a shepherd's crook. The dead leaves stay attached for months, so a tree that was in full flower in spring can look burnt and ragged by summer. In a bad year fire blight can kill young trees outright and destroy the crop on a mature tree, and it spreads fast enough that a single infected blossom can lead to a dead branch within weeks.
The cause is the bacterium Erwinia amylovora, and it is a warm, wet-weather disease that enters through the flowers in spring and through wounds in summer. Bees and other pollinators carry it from flower to flower, rain spreads it within the tree, and pruning tools carry it from branch to branch. The bacteria produce a sticky ooze that oozes from infected tissue and carries the disease further. There is no cure for an infected branch — the treatment is to cut it out, in dry weather, with clean tools — and the prevention is about resistant varieties, careful pruning, and avoiding the soft, lush growth that the bacteria love.
What fire blight looks like: symptoms
- Blossom blight: flowers turn brown and shrivel, then blacken and hang on the tree, often with the whole flower cluster affected at once.
- Shepherd's crook: the tip of an infected young shoot bends over into a hook shape as it wilts and dies, which is the most distinctive sign of the disease.
- Blackened, scorched leaves: leaves on an infected shoot turn brown or black and stay attached to the dead shoot for months, giving the tree its scorched look.
- Bacterial ooze: a sticky, amber or milky ooze may seep from infected shoots, fruit, or cankers in wet weather, and it dries into a dark crust.
- Sunken cankers: dark, sunken, water-soaked patches on branches and the trunk, often with a clear margin between the dead bark and the healthy bark.
- Fruit that rots and mummifies: young fruit blackens, shrivels, and stays hanging on the tree, and it can carry the bacteria into the following year.
- Rapid spread in a branch: the blight can run down a shoot and into the branch within days in warm, wet weather, killing the whole branch.
Fire blight starts in spring, when the blossoms open and the bacteria are carried into them by pollinators and rain. The first sign is a brown, shrivelled flower cluster, and within a week or two the shoot beyond it blackens and bends into a shepherd's crook. In warm, wet weather the bacteria run down the shoot into the branch, and a branch can be dead within a month of the first blossom blight. The disease slows in hot, dry summer weather and stops in winter, when the bacteria survive in cankers on the branches. A tree that is badly hit in one year will often show cankers that ooze in the following spring, starting the cycle again. Young trees can be killed in a single season; mature trees usually survive, but they lose branches and crops.
Which plants get fire blight
Fire blight attacks apples, pears, and other members of the rose family: crabapples, quinces, hawthorns, rowans, cotoneaster, pyracantha, and some roses. Pears are generally more susceptible than apples, and young, fast-growing trees are hit hardest. Some varieties are notably resistant and some are very susceptible, and the choice of variety is the single most important decision a gardener makes about fire blight. The disease does not attack plants outside the rose family, so your vegetables and your other fruit are safe.
Conditions that favour fire blight
Fire blight needs warm, wet weather in spring: temperatures in the 70s Fahrenheit with rain or heavy dew while the blossoms are open. The bacteria enter through the flowers and through wounds — hail, pruning cuts, and insect feeding all provide entry points — and they spread fastest in warm, humid weather. Young, vigorous trees with a lot of soft, fast-growing shoot tips are the most vulnerable, and heavy nitrogen feeding that pushes soft growth makes the disease worse. The bacteria overwinter in cankers on the branches, so a tree that had fire blight last year starts this spring with the disease already present.
How fire blight spreads
Fire blight spreads by pollinators carrying bacteria from flower to flower in spring, by rain splashing bacteria from an infected shoot to healthy tissue, and by pruning tools that cut an infected branch and then a healthy one. The bacterial ooze is a major source: insects are attracted to it and carry it to new flowers, and rain washes it down the branch. The bacteria also travel in infected nursery stock, which is why buying from a reputable source matters. Wind alone is a minor carrier compared with insects, rain, and tools — which is why clean tools and dry-weather pruning are so effective.
How to tell it apart from lookalikes
Fire blight is sometimes confused with frost damage, but frost hits the whole tree at once after a cold night and the damage is uniform, while fire blight starts in individual flower clusters and shoots and spreads from them. Bacterial canker on stone fruit makes similar cankers but on a different family of trees and without the shepherd's crook. Powdery mildew on apple makes a white coating on young shoots rather than blackening them. Drought stress browns leaves but does not bend shoot tips into a crook or produce bacterial ooze. If the shoot tip is bent like a hook and the leaves are blackened and hanging on, fire blight is the most likely answer.
Prevention: cultural steps that work
- Choose resistant varieties when you plant — fire blight resistance varies a lot between apple and pear varieties, and it is worth checking before you buy.
- Plant in full sun with good airflow, and avoid planting apples and pears where they are crowded or shaded.
- Prune in late winter, in dry weather, when the bacteria are dormant, and avoid pruning in spring and summer when the disease is active.
- Avoid heavy nitrogen feeding that pushes soft, lush shoot growth, and feed moderately instead.
- Remove wild hawthorns and other susceptible hosts near the orchard where practical, since they can carry the disease.
- Buy trees from reputable nurseries, and inspect new trees for cankers before planting.
- During bloom, avoid overhead watering, and do not work with the trees when they are wet.
Treatment step by step
- Prune out infected shoots and branches as soon as you see them, cutting at least 12 inches below the visible damage into healthy wood, and do it in dry weather so the bacteria do not spread in the wet.
- Disinfect your pruning tools between every cut — a household disinfectant or diluted bleach solution, with the tools rinsed and dried afterwards — so you do not carry the bacteria to the next branch.
- Dispose of the prunings with household waste or burn them where that is allowed. Do not compost them and do not chip them into garden mulch.
- Do not prune in wet weather, and do not prune an infected tree and then a healthy one without disinfecting the tools.
- Remove mummified fruit and dead flower clusters from the tree, since they can carry the bacteria.
- Keep the tree watered evenly and fed moderately so it can replace lost branches, but do not overfeed with nitrogen.
- At the end of the season, inspect the tree for cankers and prune them out in late winter, in dry weather, cutting back to clean wood.
What recovery looks like
Recovery from fire blight is measured in seasons, not weeks. A tree that loses a few shoots will usually push out new growth from below the cuts and recover its shape within a year or two. A tree that loses major branches will take longer, and it may never regain its original form, but it can still become a productive tree if the disease is caught early and the pruning is thorough. The sign that the plan is working is a spring with no blossom blight and a summer with no new shepherd's crooks. That is the point at which fire blight stops being a yearly crisis and becomes an occasional shoot to prune out. A young tree that is badly hit in its first year may never thrive, and replacing it with a resistant variety is sometimes the better choice.
When a plant is beyond saving
A tree is beyond saving from fire blight when the bacteria have reached the trunk and girdled it, when cankers cover the main branches, and when the tree fails to leaf out properly in spring. A young tree that is killed to the ground in one season is also beyond saving, though it may sucker from the roots — those suckers will be susceptible and are not worth keeping. A mature tree with a few dead branches is not beyond saving: prune them out, improve its care, and watch it. The disease is a long game, and a tree that is otherwise vigorous deserves the chance to live with it, provided the pruning is done promptly and cleanly.
Frequently asked questions
Can fire blight spread to my other fruit trees?
It can spread to other members of the rose family — apples, pears, crabapples, quinces, hawthorns, cotoneaster, and pyracantha — but not to stone fruit, citrus, or other families. Keep an eye on the susceptible plants near an infected tree.
Should I spray for fire blight?
Sprays are used in commercial orchards, usually at bloom time, but they are a protectant rather than a cure and they are not a substitute for resistant varieties and clean pruning. For a home garden, pruning and variety choice matter more, and any spray should be used exactly as its label directs.
Why did my pear tree get fire blight but my apple did not?
Pears are generally more susceptible than apples, and the variety matters a lot. A susceptible pear next to a resistant apple will often be hit while the apple stays clean, and the weather during bloom — warm and wet, or cool and dry — makes a big difference too.
Can I compost branches with fire blight?
No. The bacteria can survive in the prunings, and home compost rarely gets hot enough to kill them. Bag the prunings and put them with household waste, or burn them where that is allowed.
When is the best time to prune out fire blight?
In dry weather, as soon as you see it, and again in late winter when the bacteria are dormant. Never prune an infected tree in wet weather, and always disinfect your tools between cuts — and check your local extension service for the best pruning timing in your area.
Getting help and going further
If you are unsure which disease you are dealing with, take clear photos of the symptoms and check your local extension service — they can confirm a diagnosis from a sample and advise on the varieties and the timing that work best in your area. You can also try our plant disease checker to narrow down the problem, and browse the guides hub for related disease guides. For growing advice, see growing apples. For growing advice, see growing peaches. For growing advice, see zone 5 apples. Related guides: apple scab, brown rot fruit, bacterial spot. Whenever you remove diseased material, dispose of it with household waste — do not compost diseased material, since home compost rarely gets hot enough to kill the organisms that cause these diseases. Good record-keeping helps too: note the date, the weather, and the variety when a problem first appears, so you can spot the pattern next year and act earlier.