Fire Blight: How to Spot It, Stop It, and Save the Rest of the Tree

If a shoot tip on your apple or pear tree went black almost overnight and curled over into a little hook, you’re looking at fire blight. It’s bacterial, not fungal, which means the fungicide in your garage does nothing for it. Our tree fungus guide covers the fungal diseases that hit other species. This one plays by different rules, and it’s the one disease on this site where I tell people to stop reading, go outside, and start cutting the same day they spot it.

Fire blight (Erwinia amylovora) infects apple, pear, crabapple, quince, and a long list of ornamental relatives: pyracantha, hawthorn, cotoneaster, and loquat among them. On a susceptible pear, it can take a mature tree from healthy to dead in one bad spring. On an established pyracantha hedge, it usually just kills branches a few feet at a time, year after year, until you finally deal with it.

Here’s how to tell it’s fire blight, which trees in your yard are at risk, how it actually spreads, and what pruning and spraying can and can’t do about it.

How to tell it’s fire blight

Four signs, and you rarely need all four to be sure.

• The shepherd’s crook. New shoot tips die back suddenly, turn black or dark brown, and curl over into a tight hook that looks like the top of a shepherd’s staff. This is the single most reliable field identifier for fire blight. Nothing else on a fruit tree does this.
• Scorched, clinging leaves. Infected leaves and blossom clusters turn black or dark brown and look burned, which is where the disease gets its name. Unlike a healthy tree dropping dead leaves, blighted leaves usually stay attached to the branch instead of falling off.
• Bacterial ooze. During warm, wet weather, cankers and infected bark weep a watery, light tan to amber fluid that darkens as it dries. It’s sticky and often beads up on the bark surface. If you see droplets or streaks like this on a branch with dead tips above it, that confirms fire blight.
• Sunken, discolored cankers. Older infections on branches and the trunk show as darkened, slightly sunken patches of bark, sometimes with cracked edges where the bark has split away from healthy wood underneath.

Timing matters too. Fire blight symptoms show up fast, within one to three weeks of bloom, and they show up in spring on new growth, not in late summer on mature leaves. If your tree looks scorched in May and the shoot tips are curled and black, that’s fire blight. If you’re seeing blotchy brown spots on older leaves in August, you’re more likely looking at a fungal leaf spot, and our signs of a dying tree guide walks through the broader decline patterns worth ruling out first.

Which trees actually get it

Fire blight targets the rose family (Rosaceae), and within that family, some genera get hit far harder than others.

Highest risk: Pear is the most susceptible tree most homeowners plant. Bartlett, in particular, is so vulnerable that parts of California’s commercial pear industry have moved away from it specifically because of fire blight management costs. Quince and some crabapple cultivars are close behind. Apple varies a lot by cultivar and rootstock: Gala and Fuji can be hit hard, while Granny Smith shows much lighter infection in the same orchard. Dwarfing rootstocks M.9 and M.26 are notably susceptible and can carry the infection down into the trunk fast enough to kill a young tree outright.

Moderate risk, common in landscapes: Pyracantha (firethorn), hawthorn, and cotoneaster are the three ornamentals I get the most fire blight calls about. Hawthorn as a genus has few resistant options, so expect to manage it rather than plant around it. Pyracantha varies by cultivar. Clemson HGIC lists ‘Mojave,’ ‘Navaho,’ and several others as more resistant, while some older Scarlet Firethorn selections are quite susceptible. Cotoneaster also splits by species. Several spreading types (C. adpressus, C. horizontalis, C. dielsianus) show good resistance, while the popular upright cultivar ‘Autumn Fire’ does not.

Also on the list: Mountain ash, serviceberry (juneberry), photinia, spirea, toyon, and loquat can all get fire blight, generally with less severity than pear or the most susceptible apple cultivars.

If you’re planting new and fire blight is a known problem in your area (your local UC or state extension office can tell you), choosing a resistant cultivar up front saves you years of pruning. If you already have a hawthorn hedge or a mature Bartlett pear, this article is about managing what you’ve got.

How it spreads

Fire blight runs on a specific, repeatable cycle, and understanding it explains both why spraying only works in a narrow window and why “pruning it out” only works if you do it right.

1. Overwintering. The bacteria survive winter in cankers on branches, twigs, and sometimes the trunk. These are the holdover infections from last year that you may not have caught.
2. Spring ooze. As temperatures warm, especially once daytime highs push into the 60s and 70s, bacteria multiply inside the cankers and ooze out onto the bark surface in a sticky, sugary fluid.
3. Bloom infection. Bees, other pollinators, and rain splash carry that ooze to open blossoms. Blossoms are the main entry point. Warm, humid weather during bloom (roughly 75-85°F with rain or high humidity) is the exact recipe for a bad infection year. A wet, mild bloom period does more damage than a whole summer of hot dry weather afterward.
4. Shoot infection. From infected blossoms, the bacteria move into the flower stem and then into new shoots, which is where the shepherd’s crook shows up, usually one to three weeks after the initial bloom infection.
5. Secondary spread. Wind-driven rain, insects, and even pruning tools carry bacteria from actively oozing cankers to fresh wounds and succulent new growth throughout the growing season, not just during bloom.
6. Back into the wood. Left alone, the infection moves down the shoot into older wood, forming a new canker that overwinters and restarts the cycle next spring.

That’s also why hail, wind damage, and aphid or leafhopper feeding matter. Any fresh wound on a susceptible tree, not just an open blossom, is a door the bacteria can walk through during an active infection period.

Treatment: pruning is the only thing that works once you can see it

I want to be straight with you here, because a lot of fire blight advice online overstates what a spray bottle can do. Once you can see a blackened, hooked shoot tip, the bacteria are already inside that wood. No fungicide, no copper spray, no home remedy reaches bacteria that are already established under the bark. Pruning is the treatment. Everything else is prevention for next year.

Cut it out, and cut it right. Remove infected branches 8 to 12 inches below the last visible sign of infection, into wood that’s clean and uniform in color all the way through the cut. On a fast-moving spring infection, extension programs recommend erring toward the long end of that range, even 12 to 18 inches on pear, because the bacteria travel ahead of the visible dead tissue. Cut at a natural branch junction or collar when you can rather than stopping mid-branch. A pair of sharp Felco F2 bypass pruners makes a clean cut that seals faster, which matters here more than on almost any other pruning job.

Sanitize between every single cut, not just between trees. This is the step people skip, and it’s the one that actually stops the disease from spreading tree to tree in your own hands. Dip or wipe the blade with 70% rubbing alcohol, or a 10% bleach solution (1 part household bleach to 9 parts water), after every cut you make on infected wood. Cut one blighted branch, wipe the blade, cut the next. If you don’t sanitize between cuts, you’re inoculating clean wood with the same bacteria you just removed. On a badly infected pyracantha hedge with a dozen blighted branches, that’s a dozen wipe-downs, not one at the end.

Prune in the dormant season when you can, but don’t wait if it’s spreading now. Winter, while the tree is fully dormant, is the safest time to remove cankers because there’s no active bacterial ooze and no open wounds for reinfection. But fire blight doesn’t wait for your pruning schedule. If you spot an active shepherd’s-crook infection in May, cut it out immediately rather than letting it run until winter. On a hot, humid week, a small infection can move a foot or more down a branch in days.

Burn or bag what you remove. Don’t leave blighted prunings in a pile near the tree. Bag them for trash pickup or burn them if local rules allow. Composting infected wood keeps the inoculum on your property.

Spraying is preventive only, and only at bloom. Copper products and, where registered for fruit trees, streptomycin work by killing bacteria on the blossom surface before infection happens. They do nothing for an existing canker and nothing once symptoms show. Bonide Copper Fungicide applied at first bloom and again every 4 to 5 days through the bloom period is the standard home approach on apple and pear. It reduces new infections during a wet bloom season, it doesn’t eliminate the risk, and it’s worth skipping entirely in a dry spring where fire blight pressure is low. Streptomycin is not registered for use on ornamentals like pyracantha, hawthorn, or cotoneaster, so pruning and resistant cultivars are your only real tools on those plants.

For the apple- and pear-specific pruning calendar, including how fire blight changes your winter pruning cuts, see our guides to pruning apple trees and pruning pear trees.

Prevention checklist

• Inspect susceptible trees at bloom and again three weeks later. Catching a shepherd’s crook in its first week, while it’s still a foot of shoot rather than a whole branch, saves you a much bigger cut later.
• Prune out holdover cankers every winter, before bud break, on any tree or shrub that had blight the year before. This is the single highest-value fire blight task on the calendar.
• Sanitize tools between every cut on infected wood, every time, no exceptions.
• Avoid heavy nitrogen fertilizer in spring. Fast, soft new growth is exactly what the bacteria infect most easily. Feed fruit trees and susceptible ornamentals modestly, and skip a spring feeding entirely the year after a bad blight outbreak.
• Skip overhead irrigation during bloom. Wetting blossoms with a sprinkler mimics the rain conditions that spread bacteria. Switch to drip or basin irrigation at the root zone.
• Choose resistant cultivars for new plantings. Pyracantha ‘Mojave’ and ‘Navaho,’ spreading cotoneasters like C. horizontalis, and fire-blight-tolerant apple and pear rootstocks all reduce the problem before it starts.
• Don’t plant highly susceptible species next to each other. A hawthorn hedge planted 15 feet from a Bartlett pear gives the bacteria an easy bridge between hosts in the same bloom window.

When to call an arborist

Handle the routine cases yourself: a few blighted shoot tips on a backyard apple, an annual pyracantha touch-up, a hawthorn hedge that needs its yearly dead-branch removal. Call in a professional when you see any of these:

• Infection in a scaffold limb or the trunk, rather than just shoot tips. Removing a major limb changes the tree’s structure, and an arborist can judge whether the tree is salvageable.
• A young tree on M.9 or M.26 rootstock with fire blight near the graft union. These rootstocks carry infection into the trunk fast, and a tree that gets hit there can die within the season. Don’t wait to see if it clears up on its own.
• You can’t keep up with an active spring outbreak. If new shepherd’s crooks are appearing faster than you can cut and sanitize, that’s a sign the infection has outrun a homeowner-scale response.
• A high-value or mature tree where you’re unsure how much to remove. Cutting 8-12 inches below the canker on a 40-foot pear sometimes means removing a major limb. An arborist can make that call without over-pruning a tree that would otherwise recover.

An arborist consultation typically runs $75-200. Find an ISA-certified arborist through Trees Are Good. While you’re doing your spring walk-around for fire blight, it’s worth adding tree inspection to the same seasonal pass covered in a broader home maintenance checklist, since the same week you’re checking gutters and roof flashing is a good week to check bloom and new growth on any pear, apple, or pyracantha in the yard.

Frequently Asked Questions

Will fire blight kill my tree?

It can, and on pear and some apple rootstocks it kills fast. Fire blight moves from blossoms into shoots, then into branches, and if it reaches the trunk or a major scaffold limb before you prune it out, the tree can die in a single growing season. On ornamentals like pyracantha, hawthorn, and cotoneaster, it’s usually less severe and rarely fatal on an established plant, but it will kill individual branches every year if you ignore it.

Does spraying stop fire blight once I see it?

No. Copper and streptomycin only prevent new infections at open blossoms, before bacteria get into the wood. Once you can see a blackened, curled shoot tip, the bacteria are already established in that branch, and no spray reaches them. Pruning is the only treatment that does anything at that point.

How far below the canker do I need to cut?

Eight to twelve inches into wood that shows no discoloration, on a tree you can see clearly. On a hot, fast-moving infection, extension services recommend erring toward 12 inches or more, because the bacteria can move ahead of the visible dead tissue. Cut at a natural branch junction when you can, rather than mid-branch.

Why do I need to sanitize my pruners between every single cut?

Fire blight bacteria ride on your blade in the sap left behind from an infected cut. Make the next cut on healthy wood without cleaning the tool first, and you’ve just inoculated a clean branch. Dip or wipe the blade with 70% alcohol or a 10% bleach solution after every cut on an infected tree, not just between trees or between branches.

Can fire blight spread from my pyracantha to my apple tree?

Yes. Fire blight isn’t picky about which Rosaceae host it infects next. Bees and rain-splash carry the bacteria between any susceptible plant in bloom range, so a blighted pyracantha hedge or hawthorn 30 feet from your apple tree is a real infection source, not just a separate problem.

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References: UC IPM, Fire Blight (Home & Landscape); UC IPM, Fire Blight (Apple); Penn State Extension, Fire Blight in Ornamentals; Clemson HGIC, Fire Blight; Morton Arboretum, Fire Blight.