European Canker

Neonectria ditissima

Well-established cankers, showing the distinctive fungal fruiting bodies.

Image courtesy of Wendyl Nissen

Symptoms

Small lesions that spread and encircle twigs and branches, eventually causing wilting of foliage and dieback. These lesions can develop into large, sunken dead cankers if left untreated.

White pustules can appear on new cankers in summer and early autumn, during wet weather. Groups of orange or red spheres called ‘perithecia’ emerge from older established cankers in autumn, winter and spring. These structures are the fungal fruiting bodies that emit spores.

On older cankers, bark disappears from the centre and a ridge of callus can form around the edge, resembling concentric rings around the sunken infection site. Fungal mycelium extends under the bark to cause discolouration of the sapwood, spreading out from the canker site.

Canker on the branch of a pear tree.

How to Protect Your Plants

Prevent infections with regular applications of Yates Copper Oxychloride during bud burst, green tip (September), leaf fall (May) and winter dormancy.

The only reliable control for cankers is to wait for dry conditions, then physically cut out the diseased tissue and burn the offcuts. Sterilise secateurs or shears between cuts to prevent the disease spreading - wipe tool blades with methylated spirits, a 9:1 mix of water and bleach, or alcohol wipes, then rinse with water.

• Remove and burn all infected plant parts. For larger cankers, use a knife or chisel to slice out the infected tissue. When you reach healthy wood, keep going to cut an extra 20-30mm deeper than the infection, to make certain you get rid of all the diseased wood. On branches, strip back the bark around cankers to check for discoloured sapwood. If you find any, keep stripping bark to find the end of the staining, so you can cut out the discoloured tissue. When you arrive at clean sapwood, remove an extra 30-40cm margin outside it.
• For branches, consider removing the branch completely. Surgery to remove cankers from a main trunk or leader is a challenging job, and sometimes the patient won’t recover.
• Apply Yates Copper Oxychloride to the affected areas after the removal of dead tissue, then seal and protect the wounds with Yates PruneTec (which forms a barrier against spores re-infecting the cuts).
• Rake up and burn any leaf litter under the affected tree. It's also a good idea to check your other trees aren’t showing symptoms.
• Avoid applying high-nitrogen fertilisers to infected trees.
• An application of Yates Lime Sulfur during the dormant winter period will help kill off any lurking spores.

Canker on the branch of an apple tree.

Plants Impacted:

• Apples
• Pears
• Walnuts
• Maple trees
• Beech trees
• Oak trees