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Ministry of Agriculture, Food and Rural Affairs

European Canker

Older European canker produces bright orange fruiting bodies during winter A young tree completely girdled by European cankerOrange sporulation on branchEuropean canker on trunk
Click to enlarge.

Beginner

Scientific Name
Neonectria ditissima (formerly Nectria galligena)

Identification

  • Cankers appear as sunken lesions on twigs, branches, crowns, stems or trunks, surrounded by living tissue.
  • The fungus invades injuries such as those caused by old pruning wounds or leaf and fruit scars.
  • European cankers form a rough collar around a wound site, and this collar often grows larger each year.
  • Bright orange fruiting bodies containing spores are produced on cankers during winter.
  • Cankers often girdle a large limb or trunk, killing all branches beyond that point.
  • Trees infected in the nursery exhibit poor growth and eventual death.

Often Confused With

  • Anthracnose canker - European canker occurs where the tree has been injured such as pruning wounds or leaf and fruit scars. Canker enlarges each year and often contains bright orange fruiting bodies during the winter. Anthracnose canker infects healthy wood and is small lesion that doesn’t grow in size and has a fiddle string appearance
  • Fire blight canker - Fire blight canker becomes sunken with cracked margins with bacteria oozing out onto the surface of the canker. Cankers enlarge and can girdle the branch. European canker occurs where the tree has been injured such as pruning wounds or leaf and fruit scars. Canker enlarges each year and often contains bright orange fruiting bodies during the winter.

Period of Activity
Most infections occur when temperatures are 10-16°C and moisture is present. Cankers cause infection anytime after the emergence of green tip right up until harvest.

Scouting Notes
Monitor trees for cankers throughout the season. Mark infected trees with bright coloured flagging tape or spray paint to make it easier to find them and prune out infected limbs during the dormant season.

Thresholds
None established.

Advanced

Scientific Name
Neonectria ditissima (formerly Nectria galligena)

Identification           
In general, canker refers to the symptom of sunken lesions on twigs, branches, crowns, stems or trunks, surrounded by living tissue. The impact of a canker on the health and productivity of a tree depends on the location, number and size of the canker. A canker on the main trunk of a tree results in the death of the tree if it expands or girdles the trunk. A canker on a branch causes the rest of the branch beyond the canker to die or become much less productive, without affecting the rest of the tree.

The fungus invades injuries such as those caused by old pruning wounds or leaf and fruit scars. European cankers form a rough collar around a wound site, and this collar often grows larger each year. Bright orange fruiting bodies containing spores are produced on cankers during winter. Cankers often girdle a large limb or trunk, killing all branches beyond that point. Trees infected in the nursery exhibit poor growth and eventual death.

Often Confused With

  • Anthracnose canker - European canker occurs where the tree has been injured such as pruning wounds or leaf and fruit scars. Canker enlarges each year and often contains bright orange fruiting bodies during the winter. Anthracnose canker infects healthy wood and is small lesion that doesn’t grow in size and has a fiddle string appearance
  • Fire blight canker - Fire blight canker becomes sunken with cracked margins with bacteria oozing out onto the surface of the canker. Cankers enlarge and can girdle the branch. European canker occurs where the tree has been injured such as pruning wounds or leaf and fruit scars. Canker enlarges each year and often contains bright orange fruiting bodies during the winter.

Biology
Cankers form when a pathogen infects and colonizes the cambium tissue under the bark of twigs, branches, trunks or crowns of trees. The cambium tissue eventually dies and the bark adjacent to the infected cambium becomes sunken, discoloured, cracked or sloughed off.

Most infections occur when temperatures are 10-16°C and moisture is present. Orchards with poor drainage are more prone to European canker. Excessive vegetative growth also makes trees more susceptible. Ragged pruning cuts and branch stubs increase the risk of cankers developing at these wound sites. Many other woody plants such as maple, birch, hickory, poplar, beech and hawthorn are alternative hosts to this pathogen.

Period of Activity
Most infections occur when temperatures are 10-16°C and moisture is present. Cankers cause infection anytime after the emergence of green tip right up until harvest.

Scouting Notes
Monitor trees for cankers throughout the season. Mark infected trees with bright coloured flagging tape or spray paint to make it easier to find them and prune out infected limbs during the dormant season

Thresholds
There are no established thresholds for European canker.

Management Notes

  • Although fungicides reduce the spread of cankers, they are not effective at curing existing infections. It is best to prevent the establishment of cankers.
  • Keep pruning tools sharp to avoid ragged cuts or torn bark at cuts.
  • Prune during the dormant season in the winter before sap flow begins and when temperatures are too cold for the pathogen to be active. This minimizes the chance of disease organisms being spread on pruning tools.
  • Prune branches back to the collar, leaving the collar intact to heal the wound, but avoid leaving stubs.
  • Prune out all dead wood and remove fruit mummies as they both serve as reservoirs for disease organisms.
  • Remove cankers promptly by pruning the branch several centimetres below the canker. Where cankers occur on the main trunk, it is sometimes possible to save the tree by cutting away diseased tissue and encouraging the bark to heal around the wound. Surgically removing cankers on main trunks of infected trees is time consuming and often not completely successful. 
  • Remove other alternative hosts such as maple, birch, hickory, poplar, beech and hawthorn with cankers in the vicinity of the orchard.
  • Burn prunings or remove them from the orchard promptly. If this is not possible, chopping prunings hastens their breakdown and reduces the risk of disease spread.
  • Inspect nursery stock carefully before planting and discard any trees with cankers.