Fire blight

Erwinia amylovora

A bacterial disease of the apple-pear family: blossoms and shoots look scorched black and hang on. Prune 30 cm below visible damage, sterilizing tools between cuts.

Bacterium No cure Spread by insectsRain splashSpread on tools & hands Spreads to neighbors

What you'll see

Blossom trusses wilt, blacken and stay hanging on the tree instead of dropping.
Young shoot tips bend over into a shepherd’s crook while still soft.
Whole spurs and branchlets look scorched, with brown, dead leaves that refuse to fall.
A sticky amber ooze may weep from the affected bark in warm, humid weather.
Slice the bark below the damage and the inner tissue is foxy red-brown rather than green, with a clear wavy margin.

Why it happens

A bacterium that overwinters at the edge of last year’s cankers and oozes out in spring. Pollinating insects carry it straight into open blossom, and rain, wind and unsterilized secateurs move it on from there. It enters through flowers and soft growth, not through mature bark.

Warm, humid weather at blossom time — above roughly 18°C with rain or heavy dew — sets it off, and a second flush of blossom in late summer after a wet spell often carries it further. Soft, sappy growth from heavy nitrogen feeding is highly susceptible.

Treating it

Cut out affected wood promptly, at least 30 cm and preferably 60 cm below the last visible browning, into clean green wood.
Sterilize secateurs and saws between every cut with alcohol or a garden disinfectant.
Prune in dry weather and burn or bin the prunings; do not shred them on site.
If the trunk or main framework is involved, take the tree out — it cannot be saved and it will infect its neighbors.
Fire blight is a notifiable concern in some fruit-growing areas; check local guidance before you begin on a large outbreak.

Keeping it away

Choose less susceptible cultivars and rootstocks when planting apples, pears and quinces.
Avoid high-nitrogen feeds, which produce the soft shoots the bacterium prefers.
Remove and destroy any secondary blossom that appears out of season in late summer.
Inspect and cut out old cankers in winter, before the spring ooze begins.
Keep susceptible ornamentals — cotoneaster, pyracantha, hawthorn — out of an orchard.

Who gets it

Only members of the apple and pear family: apple, pear, quince, hawthorn, rowan, cotoneaster and pyracantha.