Fireblight is caused by the bacterial pathogen Erwinia amylovora, which enters the tree through wounds or flower blossoms. The leaves on the ends of a branch turn brown and bend over, creating a shepherd’s crook appearance. Branches become blackened in appearance, producing a scorched look that gives the disease its name. Fruit may shrivel or be sticky. Feeding insects may spread the disease to wounds on unaffected trees, as will pollinators to blossoms. Fireblight can also spread from branch to branch by rainwater splashing the inoculum off cankers.

Plants Affected

Plants in the Rosaceae family are susceptible to fireblight. In Grande Prairie, this will most commonly include:


Prune out infected branches at least 30 centimetres (12 inches) below any sign of cankers. Pruning tools must be sterilized between cuts using gasline antifreeze, a 10% bleach solution or in 70% rubbing alcohol. Soak your tools for at least one minute between cuts to prevent spreading the disease. Destroy pruned wood immediately.

NOTE: Fireblight is a regulated disease through the Agricultural Pests Act (PDF, 458 KB) and Regulation (PDF, 399 KB). It has been identified as having the potential to be devastating to agricultural operations in Alberta, and as such, appointed inspectors may enter onto property at any time to inspect for and treat this disease. If found on your property, the disease must be controlled.

Flagging leaves due to fireblight infection
Weeping infected wounds
Dead New Growth with expected Shepherd's crook shape