Fire Blight
Fire blight is a highly destructive bacterial disease of rose-family pome trees.
Fire Blight at a glance
| Also known as | Erwinia amylovora |
|---|---|
| Affected parts | Blossoms, shoots, leaves, branches |
| Most at risk | Rose-family pomes: crabapple, hawthorn, quince, pyracantha, cotoneaster, pear |
| Main cause | Bacteria entering via blossoms/wounds in warm, wet weather |
| Severity | Very serious and fast, can kill branches or whole trees |
| Reversible? | No cure; control only by cutting well below the infection |
What to look for
- Leaves: Blossoms, leaves, and shoots suddenly turn brown to black as if scorched; blighted leaves wilt but stay attached rather than dropping.
- Whole tree: Rapid dieback spreading from blossoms/tips down into branches; in bad cases whole sections die within weeks.
Overview
Fire blight is a highly destructive bacterial disease of rose-family pome trees. It enters through blossoms and wounds in warm, wet spring weather and moves fast through the shoots and branches, killing tissue that looks scorched, as if burned. There is no cure: the only control is prompt, drastic pruning well ahead of the visible infection, with rigorous tool sterilisation.
Causes
The bacterium Erwinia amylovora spreading via rain, insects, and tools; entry through open blossoms and wounds; warm (24 to 30 °C) humid weather during bloom; and soft, lush (over-fed) growth.
Commonly confused with
Drought/frost dieback browns growth but lacks the shepherd's crook and bacterial ooze. Fungal canker is slower and more localised. The combination of scorched look, clinging blackened leaves, shepherd's-crook tips, and amber ooze is diagnostic of fire blight.
Which species are affected
Rose-family pomes only: crabapple, hawthorn, Chinese and Japanese flowering quince, pyracantha, cotoneaster, pear, mountain ash, and relatives. (Pomegranate, despite the name, is not a pome and isn't affected.)
Treatment
There is no cure. Prune out infected wood 20 to 30 cm (8 to 12 in) below the visible damage, ideally in dry/dormant conditions, sterilising the tool between every single cut (10% bleach). Bin or burn prunings, never compost. Avoid heavy nitrogen and don't prune in wet weather. Copper or (where permitted) streptomycin sprays at bloom give some protection in high-risk seasons.
Fix it
What the treatment above uses, from our shop:
Step by step: Pruning vs. Pinching: Shaping Your Bonsai
Prevention
Choose resistant cultivars; avoid lush over-fed growth; sterilise tools between cuts; remove infected wood promptly; protect blossoms in warm wet springs; keep susceptible species apart.