What is it?
Fire blight is a destructive bacterial disease of fruit trees in North America. It is often seen in crabapple, apple, mountain ash, hawthorn, plum, cotoneaster, raspberry, flowering almond, and saskatoon. Fire blight can spread through rain, wind, insects, birds, and contaminated pruning tools.
Symptoms
- Flowers wilt and turn brown suddenly in spring time; leaves and twigs turn brown and curl; fruits turn dark and shrivel. Infested parts appear burned or scorched.
- Infested leaves and fruits remain attached to the tree, even in winter.
- The bark may appear sunken and dark, and can be cracked or peeling. Droplets of bacterial ooze can be found along infected parts in humid weather or after rain.
Damages
- Damage spreads quickly in warm, humid weather. The bacteria can survive winter in infested trees and emerge when flowers bloom. It can also spread via rain, splashing water, pollinators, and wounds.
- It can cause branch dieback and plant death with heavy infestation.
What to do?
- Prune out infested branches in winter when the tree is dormant and the bacteria is less active.
- Sterilize pruning tools between each cut if pruning is needed during the growing season. Use a solution of 1 part bleach to 3 parts water.
- Rake and dispose fallen leaves in fall and winter.
- Remove the entire tree if it cannot be saved to prevent the disease from spreading to other healthy plants.
- Avoid planting susceptible varieties and species, including Royalty and Pyramidal Siberian flowering crabapples, pears, European cotoneaster, and European mountain ash.
Other resources:
https://tidcf.nrcan.gc.ca/en/diseases-caused-by-pathogens/factsheet/176