Fire Blight on Rochester Pears and Crabapples: The Shepherd's Crook Warning Sign

By Linda Marsh, Pests & Diseases. Last updated: June 25, 2026

Fire blight moves fast, and it fools people. A homeowner in Penfield or Pittsford glances at a pear tree in late June, sees a cluster of leaves that look burned by a blowtorch, and assumes the tree got sprayed or sun-scorched. It did not. That scorched look, paired with a branch tip curled into a tight hook, is the signature of Erwinia amylovora, the bacterium behind fire blight. Knowing the two-part ID and one critical pruning rule can save the tree.

What does fire blight look like on a Rochester pear or crabapple?

Fire blight has a look that, once you have seen it, you cannot unsee. The two telltale signs together are the diagnosis.

First, the scorched appearance. Infected blossoms, leaves, and young shoots turn brown to black and stay attached to the branch, hanging on instead of dropping. The whole tip looks like fire ran up the branch. On pears the color tends toward inky black; on crabapples and apples it can read as reddish brown.

Second, the shepherd's crook. As the bacteria kill a young, still-flexible shoot from the tip down, the dying tip wilts and bends over into a tight candy-cane hook. That curled, blackened tip is the single most reliable visual marker of fire blight, and it separates the disease from look-alikes such as winter dieback or leaf scorch from drought. If you are seeing browning without that hook, work through the possibilities in our guide to why tree leaves curl, yellow, and die before you assume the worst.

You may also notice droplets of cream-colored to amber bacterial ooze on infected bark in warm humid weather, and sunken, darkened cankers where the infection has reached older wood. Those cankers are how the disease overwinters in Monroe County.

Which trees and shrubs get fire blight here?

Fire blight only attacks plants in the rose family (Rosaceae), but that family includes some of the most popular ornamentals and fruit trees across the Rochester area:

• Pears, both ornamental (the now-discouraged Callery and Bradford types) and edible
• Crabapples and apples, especially susceptible varieties
• Hawthorn, mountain ash, serviceberry, cotoneaster, pyracantha, and quince

Susceptibility varies enormously by cultivar. If you are choosing replacements, lean toward resistant varieties so the tree is not constantly under threat.

Why is summer the worst time to prune fire blight?

This is the part most homeowners get backwards, and it is the difference between containing the disease and spreading it.

Erwinia amylovora travels in moisture. Every time you make a cut, you create an open wound, and your pruning tool carries living bacteria from one branch to the next. In warm, humid, lake-effect Rochester summers, those conditions are exactly what the bacterium wants. Pruning an actively infected tree in July often does more damage than the disease was doing on its own, because you hand the bacteria fresh entry points and a free ride on your blades.

The rule that arborists follow: remove fire blight strikes during the dormant season, in the cold of winter when the bacteria are inactive and not multiplying. Getting that timing right for a disease-prone tree is one of the clearest cases for bringing in a professional, which our guide to when to call an arborist instead of going DIY walks through. The only exception is an aggressively spreading active infection that threatens to girdle the trunk, and that judgment call is exactly when you want a certified arborist, not a guess.

How do you cut out fire blight without spreading it?

When removal is warranted, technique is everything. Cornell's fire blight guidance lays out a three-part standard, and none of the steps is optional.

1. Cut well below the visible infection. Per Cornell, make the cut 8 to 12 inches below the lowest sign of dead or discolored tissue, into healthy wood, because the bacteria run ahead of the symptoms you can see.
2. Sterilize between every single cut. Cornell calls for dipping or wiping blades in 70% rubbing alcohol (or a fresh 10% bleach solution) after each cut, every time, no exceptions. Skipping this step is the most common way homeowners turn one infected branch into a tree-wide problem.
3. Remove and destroy the cuttings. Bag and trash or burn infected wood. Do not compost it and do not leave it on the ground, where it can harbor bacteria.

Cankers on larger limbs also need attention, since they are the overwintering reservoir. This is the same disciplined, sanitation-first approach that controls other Rochester tree diseases like black knot on cherry and plum, where infected wood must be cut out cleanly rather than left to spread.

Can you prevent fire blight in the first place?

You cannot eliminate the bacterium from the landscape, but you can make your trees far less hospitable to it.

• Avoid heavy nitrogen fertilizer, which pushes the soft, fast new growth that fire blight infects most easily.
• Skip aggressive pruning that triggers a flush of vulnerable shoots.
• Choose resistant cultivars when replanting.
• Protective sprays at bloom (copper or, for serious cases, specific bactericides) can reduce blossom infection, but timing is tight and tied to bloom-stage weather models. This is genuinely a job for a professional plant health care program rather than guesswork.

Because fire blight thrives on the same young tissue that other springtime diseases attack, an integrated approach pays off. Many of the same orchard-family trees in Rochester also battle fungal problems like apple scab on crabapples, so a coordinated plant-health-care plan often addresses several issues at once.

FAQ

Will fire blight kill my pear or crabapple tree? It can, especially on highly susceptible varieties or when an infection reaches the trunk and girdles it. Many established trees survive with prompt, correctly timed removal of infected wood, but a severe or trunk-level infection can be fatal.

Can I just cut off the burned branches now to stop it? Cutting during warm, humid summer weather usually spreads fire blight rather than stopping it, because your tools carry the bacteria to fresh wounds. Unless the infection is racing toward the trunk, wait for dormant-season pruning and sterilize between every cut.

Is fire blight contagious to my other trees? Yes, within the rose family. Rain, wind, insects, and especially unsterilized pruning tools move Erwinia amylovora from an infected pear or crabapple to nearby susceptible trees, so sanitation matters.

Why do the dead leaves stay on the branch instead of falling? That clinging, scorched, still-attached foliage is a classic fire blight trait and helps distinguish it from drought scorch or normal leaf drop. The bacteria kill the tissue so quickly that leaves dry in place rather than forming a normal drop layer.

Should I remove a pear tree that gets fire blight every year? If a tree is chronically reinfected and serving as a reservoir for the rest of your landscape, replacement with a resistant cultivar is often the smarter long-term call. A certified arborist can assess whether the tree is worth saving or better removed.

Sources

• Monster Tree Service of Rochester
• Cornell Integrated Pest Management: Fire Blight (Erwinia amylovora) Fact Sheet
• Cornell Garden-Based Learning: home gardening resources
• USDA Agricultural Research Service