Image of the City of Regina

Fireblight

Picture of a saskatoon bush with fireblightInfects

Apple, Pear, Spirea, Crabapple, Mountain Ash, Hawthorn, Cotoneaster, Raspberry, Saskatoon, Plum and Chokecherry trees and shrubs

Symptoms

The first sign of the disease is sudden wilting and browning of flowers, followed by scorching of the foliage. Leaves and blossoms sometimes cling to the branches instead of falling.

Infected growing tips often bend to form a “Shepherd’s Crook” shape.

In warm, humid weather, droplets of clear oramber liquid may seep from recently infected areas.

Dark, sunken areas called cankers can form on stems.

Fruit shrivels and turns from brown to black and will persist on hanging from the tree.

Cause

Fireblight is a serious bacterial disease that spreads easily between trees, especially in wet, windy weather.

Cure

There is no cure, only control.

IMP Toolkit

Preventative tools

  • You can apply a Bordeaux mixture to the tree following the label’s directions to act as a protective spray. To obtain best results, it should be applied 3 times:
    • At early blossom (10% of plant is in bloom)
    • At full blossom
    • At late blossom (only a few petals remain)
  • Avoid the use of high nitrogen fertilizers which promote susceptible growth.

Physical tools

  • Prune and destroy infected branches as they appear. Prune 20-25 cm below the infected area since the bacteria extends into the wood farther than the visibly infected area.
  • Sterilize pruning tools between cuts with 10% bleach or gasline antifreeze (methyl hydrate) in a spritz bottle.

Biological tools

  • Not applicable

Chemical tools

  • See Bordeaux spray mentioned in preventative tool section above.