Pear Tree Diseases: Fire Blight and the Rest You Need to Know

Pears get fewer diseases than peaches, but the one disease they do get most spectacularly, fire blight, is the worst one any backyard fruit tree can pick up. A single bad fire blight year can kill a mature pear, and pears are uniquely susceptible to it.

Five diseases account for almost everything that goes wrong on backyard pear trees: fire blight, pear scab, pear trellis rust, Pseudomonas blossom blast, and sooty blotch & flyspeck. Two of those (fire blight and sooty blotch) overlap with apple. The other three are pear-specific in their management, even when the pathogen is in the same family as something on apple.

Here’s how to identify what’s wrong with your pear tree, what to do about it, and which problems require professional help.

How to tell which disease you’re looking at

Quick visual triage. Match the most obvious symptom and jump to the section below.

• Blackened shoot tips curled into a shepherd’s crook, sticky tan ooze on the bark: fire blight
• Small olive or brown spots on leaves and fruit; corky black scabby patches on the fruit: pear scab
• Bright orange or yellow spots on the upper leaf surface, with strange acorn-shaped “trellis” structures on the underside in late summer: pear trellis rust
• Black, dead, water-soaked blossoms in spring after a frost or cool wet week: Pseudomonas blossom blast
• Smudgy dark blotches and pinpoint black dots on the fruit skin in late summer: sooty blotch and flyspeck

Most pear disease problems trace to the spring infection window during bloom. Get the late-winter and bloom-time spray decisions right and you’ll handle most of what pear throws at you.

Fire blight

Fire blight (Erwinia amylovora) is the most dangerous disease a backyard pear can get. It’s the same bacterium that hits apples (covered in our apple tree diseases guide), but pears get it worse. Bartlett pears are so susceptible that California’s commercial pear industry has shifted away from Bartlett in some regions because of fire blight management costs. If you’ve planted a Bartlett, Bosc, or Comice in your yard, fire blight is the disease you need to learn first.

What it looks like

Same symptoms as on apple, but typically more dramatic on pear:

• Shoot tips with blackened, oily-looking dead tissue, the tip curled into a tight “shepherd’s crook”
• Blossom clusters wilting and turning black, often dripping a sticky tan exudate that hardens into beads on the bark
• Entire scaffold limbs can die back within weeks of an aggressive infection
• Cankers appear at the base of dead branches, sunken, dark, often with droplets of bacterial ooze in warm wet weather

The disease can race through a young pear in a single season. Mature pears resist it better but still lose major branches in bad years.

Why it happens

The bacteria overwinter in cankers on the tree and ooze out during warm wet weather. Bees and other pollinators carry the bacteria to open blossoms during bloom. UC IPM notes that infections take off when bloom-time temperatures hit roughly 60°F with humidity above 80%, which is the standard NorCal spring rain pattern and exactly the wet-spring profile most of the eastern US sees.

Cultivar matters enormously on pear. Highly susceptible: Bartlett, Bosc, d’Anjou, Aurora. Moderately susceptible: Comice, Seckel. Resistant: Harrow Sweet, Magness, Moonglow, Maxine, Kieffer (the classic resistant “old” pear). For a new planting in a fire-blight-pressure region, choose resistant cultivars at the nursery. No spray schedule cures a Bartlett the way picking a Magness from day one does.

What to do about it

This is the only disease in this guide where the response needs to happen the day you spot it.

1. Prune out infected branches at least 12 inches below the last visible symptom, ideally 24 inches if you can spare the wood. Cut into clean white wood.
2. Sterilize your pruners between every cut. Wipe blades with 70% rubbing alcohol or dunk them in a 10% bleach solution (1:9 with water). Skip this step and you’ll inoculate every branch you touch. Felco F2 Bypass Pruners work well for fire blight because the blade disassembles for cleaning.
3. Burn or bag the prunings. Don’t compost.
4. Avoid heavy nitrogen fertilization. Excess nitrogen produces the lush succulent growth fire blight bacteria target. For nutrient timing through the growing season, the seasonal fertilizing guide on mklibrary.com lays out a calendar that minimizes fire-blight-friendly soft growth.
5. Dormant copper spray. Trees with prior fire blight history benefit from a copper application at silver tip (early bud break, when the first scales separate) to reduce overwintering bacteria. Bonide Copper Fungicide at full label rate works for home growers. Streptomycin sprays during bloom are more effective but restricted in many states.

How to keep it from coming back

The single best prevention is dormant-season inspection. Walk the tree every January with a pair of pruners and look for sunken, cracked, dark cankers on the branches. Those are next spring’s launching pads. Cut them out before bud break. Combine conservative fertilization, resistant cultivars, and aggressive winter sanitation, and most yards stay fire-blight-manageable.

For more on dormant pruning technique, see our pear tree pruning guide. It covers cut placement, sterilization, and the difference between maintenance pruning and disease pruning.

Pear scab

Pear scab (Venturia pyrina) is related to but distinct from apple scab (Venturia inaequalis). The two diseases look similar, follow similar life cycles, and respond to similar treatments, but they don’t cross-infect: pear scab only attacks pears, and apple scab only attacks apples.

What it looks like

Small olive-green to nearly black velvety spots on the upper leaf surface, similar to apple scab but often smaller and more visible on the underside than the upper side. On the fruit, scab produces dark corky lesions that can crack the skin and let in secondary infections. Severely infected fruit becomes deformed and unsaleable. Twigs and shoots also develop lesions, which the apple version rarely produces. Those twig lesions become entry points for canker diseases.

Why it happens

The fungus overwinters in fallen leaves and in last-year’s twig lesions, then releases ascospores during spring rains. According to the UMass Tree Fruit Management Guide, infection requires leaves to stay wet for 10-25 hours at the right temperatures, and symptoms appear 2-3 weeks later. Pear scab ascospores can release at night, unlike apple scab which is mostly daytime-released, which makes spray timing slightly harder.

What to do about it

• Spray timing: begin fungicide applications at green tissue emergence (just as buds break) and continue at 7-10 day intervals through bloom. Captan, myclobutanil, or copper-based fungicides all work for home growers. For backyard trees with only mild scab, a single copper application at green tip plus one at pink (just before bloom) covers most of the primary infection window.
• Sanitation: rake or shred every fallen pear leaf in autumn. Like apple scab, leaf litter is the primary spore source. A late-fall urea application accelerates leaf breakdown, but most home growers find raking simpler.
• Open canopy: prune in winter so the interior of the tree dries faster after rain. Wet leaves are how the fungus reinfects.

How to keep it from coming back

Pear scab tends to be cyclic: a wet spring produces a bad year, a dry spring almost no infection. Cultivar resistance is harder to find on pear than on apple, but Magness, Moonglow, and some of the disease-resistant Asian-European hybrids resist scab. If your tree gets hammered three years in a row with weather permitting, consider replacing or grafting over to a resistant variety.

Pear trellis rust

Pear trellis rust (Gymnosporangium sabinae, also called European pear rust) is the newest disease on this list. According to UConn Home and Garden Extension, the disease was first reported in Ontario in 2007, Michigan in 2009, and Connecticut by 2012. It’s spreading across North America and showing up in backyards that have never seen it before.

The disease is named for the distinctive trellis-like structures that develop on the underside of pear leaves in late summer.

What it looks like

In spring and early summer, look for bright yellow-orange spots on the upper leaf surface, sometimes with a red border, similar to cedar-apple rust. By late summer, the underside of those spots develops acorn-shaped fruiting structures with open “trellis” sides that release spores back to junipers. Heavy infections can cause complete defoliation by late summer and crop loss.

On junipers (the alternate host), look for persistent woody galls on the branches that produce spores year after year. Unlike cedar-apple rust galls (which produce spores once and die), pear trellis rust galls remain active for multiple seasons.

Why it happens

Pear trellis rust requires two completely different hosts to complete its life cycle, alternating between a pear tree in summer and a juniper or eastern red cedar in winter. The fungus cannot survive without both species present somewhere in the landscape. Per UConn, the most commonly planted susceptible junipers in suburban yards are Chinese juniper, savin juniper, Rocky Mountain juniper, and eastern red cedar. The resistant species worth substituting are common juniper, creeping juniper, and singleseed juniper.

What to do about it

• Locate and remove susceptible junipers within 100-1,000 feet of the pear tree. UConn specifically recommends 100-1,000 feet of separation. In suburban yards that’s often impossible without a neighbor conversation, so cultivar selection on the juniper side becomes the practical option.
• Replace removed junipers with resistant species: Juniperus squamata and J. horizontalis don’t host the fungus.
• Prune juniper galls in late winter, before April, before the orange tendrils develop. Cut into clean wood and dispose of the prunings in trash.
• Remove infected pear leaves before mid-August, before the trellis structures release spores back to junipers. This breaks the cycle.
• Fungicide as last resort: spring fungicide applications at the same timing as pear scab (green tip through bloom) can suppress new infections on the pear, but won’t help if the local juniper population is heavily infected.

How to keep it from coming back

The geographic spread of pear trellis rust is ongoing, so this is a disease worth knowing about even in regions where you haven’t seen it yet. For a new pear planting in any region with junipers nearby, scout the local landscape for galls on cedar or juniper foliage before planting. A clean local juniper population means low rust pressure. Heavy local infection means you’re better off picking a different fruit tree or finding a way to coordinate with the neighbor about juniper removal.

Pseudomonas blossom blast

Pseudomonas blossom blast (Pseudomonas syringae) is the disease that blackens pear blossoms in spring after a frost or cold rain event. It’s caused by the same bacterium responsible for bacterial canker in cherries and stone fruits, but the pear symptoms are mostly limited to blossoms rather than bark.

What it looks like

Blossoms turn black and water-soaked, often in days, after a cold wet weather event during bloom. The base of the cluster may show small black lesions. Unlike fire blight, blossom blast usually stops at the blossom level and doesn’t progress down the spur into the wood. In severe cases, twig dieback and dormant bud death also occur.

Symptoms can be confused with fire blight in the first few days. The distinction: fire blight bacteria ooze sticky tan exudate and the infection progresses rapidly down the shoot. Blossom blast stays at the blossom level and is associated with cold rather than warm wet weather.

Why it happens

The bacteria are present on healthy bud surfaces and tree bark in low populations year-round. Cool wet weather during bloom (especially frost injury) creates entry points and lets bacteria multiply. Per Pacific Northwest Pest Management Handbook research, “severe outbreaks of blossom blast on pears are usually associated with spring frosts because frost injury provides entry sites for infection.”

Cultivar susceptibility per PNW research: severely affected are Packham’s Triumph, Bartlett, Eldorado, Anjou, and Bosc. Less affected are Comice, Forelle, red Anjou, and red Bartlett.

What to do about it

• Delayed-dormant copper spray (a copper application about a month before bloom) reduces bacterial populations on bud surfaces. This is the highest-impact home-garden control.
• Prune out symptomatic wood in dry late-winter weather. Sterilize tools between cuts.
• Don’t fertilize heavily in late summer. Late-season nitrogen produces soft growth that doesn’t cold-harden, increasing frost-injury risk and the bacterial entry it provides.
• Site selection matters: pears in frost pockets (low-lying areas where cold air settles on spring nights) get blossom blast every year. A protected site on a slope or near a building drastically reduces incidence.

How to keep it from coming back

The disease tracks weather more than anything else. Years with no spring frost during bloom rarely produce significant blast. Years with multiple frost events during bloom always do. For backyard growers, the strategy is reducing the bacterial population (dormant copper) and protecting the tree from frost (site selection, possibly frost blankets during critical bloom nights for valuable trees).

Sooty blotch and flyspeck

These are the same fungal complex that hits apples, covered in detail in our apple tree diseases guide. The pear-specific story:

• The blotches and flyspeck dots show up on the fruit skin in late summer in humid, shaded conditions
• The fruit underneath is fine and edible. The blemishes are skin-deep.
• Open-canopy pruning solves most of it without spray. Pear trees that grow into a dense ball get sooty blotch; pear trees pruned to an open-vase or central-leader form don’t.

For backyard growers, sooty blotch is a cosmetic issue that needs no action unless you’re growing fruit for sale. Peel or wipe the surface and the pear eats normally.

When to call an arborist

Most pear diseases are home-garden problems and the homeowner can handle them. Three situations are different.

First, fire blight that has reached the trunk or central leader and you’re not confident about cutting back to clean wood. The cost of removing too little is the tree’s life; the cost of removing too much is a hatrack. A trained eye matters.

Second, an unfamiliar canker pattern on a mature pear, where you can’t distinguish between fire blight cankers, Pseudomonas cankers, and Cytospora canker. Different treatments, and getting it wrong is expensive.

Third, suspected pear trellis rust in a region where the disease hasn’t been previously confirmed. County extension agents and certified arborists can collect samples for lab testing and document the geographic spread.

An ISA-certified arborist consultation runs $75-200 in most US markets. Find one through the Trees Are Good arborist locator or read our guide to what an arborist does before you call.

If the tree is past saving, tree removal on a mature pear typically runs $400-1,500.

Prevention checklist

Seven habits handle most pear disease problems:

• Pick resistant cultivars at planting. Magness, Moonglow, Harrow Sweet, and Kieffer resist fire blight far better than Bartlett or Bosc. The trade-off is fruit quality, but for a backyard tree the difference between losing a Bartlett to fire blight and harvesting a slightly less elegant Magness is no contest.
• Walk the tree every January with pruners. Cut out every visible canker (12+ inches below into clean wood), every dead twig, every fire blight strike from the prior season. Sterilize blades between cuts.
• Dormant copper spray in late winter at silver tip. Reduces overwintering fire blight inoculum and Pseudomonas populations.
• Spring fungicide for pear scab at green tip and pink (just before bloom). Single most important scab control.
• Sanitation: rake fallen leaves in autumn. Reduces scab and rust spore loads.
• No heavy summer or fall nitrogen. Soft growth attracts fire blight and frost injury attracts Pseudomonas.
• Scout the neighborhood for juniper galls. If you have pear trellis rust pressure, removing or replacing susceptible junipers within 100-1,000 feet of the pear tree is the only durable control.

For broader fungal disease diagnosis across the rest of your yard, see our tree fungus guide. If you also grow apples, the apple tree diseases guide covers the closely related fire blight, scab, and sooty blotch problems on the related species. Brown rot and Cytospora canker (covered in the peach and cherry disease guides) rarely affect pears, but if you grow stone fruits in the same yard, the disease pressure connects through shared spray schedules.

Frequently asked questions

What is the most common pear tree disease?

Fire blight is the most dangerous and the disease most pear growers learn first. Pear scab is the most common in wet-spring regions. Pear trellis rust is the fastest-spreading new disease and worth knowing even if you haven’t seen it yet. Pseudomonas blossom blast hits every spring with frost during bloom but rarely kills trees. Sooty blotch is purely cosmetic.

Can I save a pear tree with fire blight?

Sometimes. Catch it early (small shoot tips affected, not yet into major branches), prune 12-24 inches below visible symptoms with sterilized tools, and the tree usually survives. If fire blight has reached the trunk or central leader, the tree is finished. Cultivar matters: Magness and Moonglow recover well, Bartlett often doesn’t.

What’s the difference between fire blight and Pseudomonas blossom blast?

Both blacken blossoms and produce some twig dieback. Fire blight ooze is sticky and tan, the infection progresses rapidly down the shoot into the wood, and warm wet weather drives it. Pseudomonas blast usually stays at the blossom level, doesn’t ooze, and follows cool wet or frost weather during bloom. Fire blight kills trees. Blast usually doesn’t.

Are pear diseases contagious to apples?

Fire blight crosses freely between pears, apples, hawthorns, and ornamental crabapples (all in the rose family). Sooty blotch crosses between pears, apples, and a few other fruits. Pear scab does NOT cross to apples (different fungal species). Pear trellis rust requires juniper as alternate host and does not move to apples. If you grow both apples and pears, treat fire blight as a single yard-wide disease and prune both on the same schedule with sterilized blades.

When should I spray my pear tree?

Two anchor sprays handle most disease pressure. First: dormant copper at silver tip (early bud break, late February through March in zones 7-9). Knocks back fire blight and Pseudomonas inoculum. Second: a scab fungicide at green tip and again at pink (just before bloom). For pear trellis rust pressure, add a copper application during the spring infection window. For most backyard pears, two well-timed spring sprays do more than five poorly timed ones.

Will pear trellis rust kill my tree?

Usually not by itself. The disease causes leaf damage and crop loss but rarely kills a healthy mature pear. Repeated heavy infections weaken the tree over multiple years, making it more vulnerable to other diseases. The bigger problem with pear trellis rust is that you can’t cure it without juniper-host management, which is often impractical in suburban yards.

Should I replace my Bartlett pear with a resistant cultivar?

If fire blight has hit it twice or more, yes. Bartlett is the most susceptible cultivar in commercial production, and the maintenance cost of keeping it alive in a fire-blight-pressure region adds up fast. Magness and Moonglow are good resistant replacements with respectable fresh-eating quality. Kieffer is the canonical canning pear, ugly but bulletproof. A 5-gallon nursery tree of any of these runs $40-80 and starts producing in 3-5 years.