Plant Problem Diagnostic
Fire Blight (Erwinia amylovora): Identification and Cultural Management
The short answer
Fire blight is a bacterial disease caused by Erwinia amylovora that attacks members of the rose family, most seriously apples and pears but also crabapple, pear, quince, hawthorn, cotoneaster, pyracantha, and mountain ash. The tell-tale sign is shoots and blossoms that suddenly wilt, blacken, and look scorched, with the shoot tip often bending into a hook shape (a shepherd's crook). In humid weather you may see droplets of tan, amber, or milky bacterial ooze on infected tissue.
There is no spray that cures an infected plant. The core of home management is cutting out infected wood well below the visible canker, sanitizing tools between cuts, choosing resistant varieties, and avoiding practices that push soft, susceptible growth. If a valuable tree is heavily affected or you are unsure of the diagnosis, contact your local Extension office or a certified arborist before removing large limbs.
How to identify it
Fire blight moves fast in warm, wet spring weather during and just after bloom. Infections often start at flowers, then spread down the shoot into branches and, in severe cases, the trunk.
- Blossoms and young shoots wilt and turn brown to black, appearing scorched or burned
- Shoot tips bend over into a candy-cane or shepherd's-crook shape
- Sunken, discolored cankers form on branches at the leading edge of infection
- Bacterial ooze (white, amber, or reddish, drying to a varnish-like film) may appear on infected bark or fruit
Conditions that favor it
- Warm temperatures combined with rain, hail, or high humidity around bloom
- Wounds from wind, insects, or hail that let bacteria enter
- Vigorous succulent growth, often from heavy nitrogen fertilizing or hard pruning
- Nearby infected host plants and insects or splashing water that carry bacteria
Cultural management steps
- 1Prune out infected wood — Remove blighted shoots and branches well below the visible canker margin, ideally during dry dormant-season weather when the bacteria are least active.
- 2Sanitize between cuts — Disinfect pruning tools between each cut to avoid spreading bacteria; follow the label on any disinfectant you use.
- 3Choose resistant varieties — When planting apples, pears, or ornamentals in the rose family, select cultivars and rootstocks rated resistant to fire blight for your region.
- 4Avoid pushing soft growth — Go easy on nitrogen fertilizer and heavy pruning, which encourage the succulent shoots that are most vulnerable.
When to escalate
If cankers reach the trunk or main scaffold limbs, if a large or valuable tree is involved, or if you are not certain the problem is fire blight, get expert help. Bactericide or antibiotic timing is highly specific and regulated, so consult your local Extension office for a current, region-appropriate recommendation and follow the label.
⚠ Never prune actively oozing fire blight in wet weather with unsanitized tools; you can spread the bacteria to healthy wood. When in doubt about diagnosis or large cuts, contact Extension or a certified arborist.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- University of Minnesota Extension — Fire blight — Symptoms (scorched shoots, shepherd's crook, bacterial ooze), host range in the rose family, spread, and pruning/sanitation management
- Utah State University Extension — Fire Blight Annual Management Guide — Erwinia amylovora affects apples and pears; pruning below cankers and resistant varieties are core management