European canker of apple is caused by the fungus Neonectria ditissima (previously called Neonectria galligena and Nectria galligena). It is only a problem in high rainfall areas, particularly Auckland and Waikato and periodically Gisborne and Nelson.

Infection spreads to new orchard blocks from neighbouring infected trees and from nursery infection. It spreads gradually within orchards, causing death of branches and preventing the maintenance of proper tree structure for fruit production. It substantially increases winter pruning costs. It can require the complete removal of orchard blocks if control practices are not properly followed. N. ditissima can cause a fruit rot, which is not a problem in New Zealand.

 Inactive   Active   Less active 

In late winter and early spring, new infections become visible as the bark starts to flake. Wilted young shoots and flower clusters are visible in spring when cankers girdle the shoot. During spring, the lesions rapidly increase in size and cracks in the bark deepen. White sporodochia with conidia are formed in the cracks and in the lenticels of the infected shoots. Older cankers may form concentric rings caused by callus formation followed by canker growth. Bright red perithecia become abundant in older cankers, in winter and spring, giving the canker a red hue, especially in the cracks.
Cankers are often visible around buds, leaf scars, picking wounds, and other open wounds, because both conidia and ascospores infect wounds. Conidia are rain-splashed, and ascospores are wind and rain dispersed.

• First symptoms are small dark purple/brown sunken areas on the bark
• The cankered area becomes blackened and sunken with concentric rings of cracking
• Swelling of the stem occurs above and below the sunken area
• Flaky bark may be present near the canker, but this is not unique to European canker
• Staining of vascular strands occurs in the wood below the canker when the bark is cut away
• White spores (conidia) are produced in the concentric cracks during humid weather, especially in spring and autumn. Conidia are spread by rain splash
• Dark red fruiting bodies (perithecia) are produced in autumn and winter. These produce ascospores that are released by rain and spread by wind.

• Pruning cuts
• Leaf scars left after autumn leaf fall
• Growth cracks in the bark where spurs or lateral branches emerge
• Rubbing wounds
• Wounds where branch ties have been

Dominant in areas with high rainfall and prolonged periods of wetness

Infection can occur throughout the year, whenever wounds are available. Canker symptoms occur throughout the year. Infected picking wounds express late winter, and infected leaf scars in spring.

The most effective fungicides for spring/summer use are:

• Carbendazim, e.g. Bavistin, MBC, Prolific (registered for black spot control)
• Captan (registered for black spot and powdery mildew control)

Protect leaf scars during leaf fall with copper oxychloride, Bordeaux mixture/Cuprofix®, Captan, Eurogel® or freshly made slaked lime.

Try to minimize copper use and do not use Copper sulphate (bluestone) [unless it has been incorporated into Bordeaux mixture] or copper hydroxide formulations.

• Removal of all visible cankers during winter pruning is essential
• Infected wood may extend some distance from the visible canker. Make pruning cuts at least 300mm below the lowest canker. Scraping cankers may not remove all infection.
• Do not prune during rain
• Ensure pruning wounds are painted with a pruning paint/paste (e.g., Bacseal. Super) that includes carbendazim at 25g/. or spraying with EurogelR, copper oxychloride, Bordeaux mixture/CuprofixR or freshly made slaked lime (pH 11+) immediately after pruning but before rain.
• It may be necessary to remove a whole limb or entire tree.
• Hygiene is critical. Sterilise pruning equipment between trees if infection is evident and remove all infected material from the orchard and destroy by burning.

More detail about European canker and its management under NZ conditions can be found here