How to Spot and Stop Apple Canker Before It Kills Your Fruit Trees

Gardening · Published 30 September 2026 Swipe more like this →

In short: Apple canker is a persistent fungal disease that turns healthy bark into sunken, dead patches. If left unchecked, it can girdle branches and eventually kill them. By acting early to prune infected wood and seal the wounds, you can protect your trees and keep them productive for years to come.

Apple canker, caused by the fungus Neonectria ditissima, is a common threat to apple trees, though it can also affect pears and Sorbus species. The disease typically manifests as round or oval sunken areas of dead bark. On smaller twigs, the infection can girdle and kill the stem within a single season, while on larger branches or the trunk, it creates lesions that may show concentric rings of growth. As the tree attempts to heal, it may develop raised edges around the wound, but the fungus often continues to spread until the branch weakens or breaks.

The fungus spreads through spores released in two ways: white pustules dispersed by water in summer, and airborne spores from small red structures during winter and spring. These spores enter the tree through wounds, including pruning cuts, leaf scars, frost damage, or injuries from scab disease and woolly aphids. Because the fungus thrives in wet, heavy, or acidic soil, managing drainage and soil pH via liming can help mitigate the risk. While no apple variety is entirely immune, some, such as 'Alfriston' and 'Grenadier', show more resistance than others like 'Cox’s Orange Pippin'.

To manage an active infection, you must prune away all affected smaller branches and spurs entirely. For larger branches, cut out all infected material until you reach healthy, green tissue. It is critical to paint these fresh cuts immediately with a protective wound sealant to prevent reinfection. Because there are no chemical fungicides available to home gardeners for controlling this disease, physical removal and careful maintenance remain the most effective strategies for preserving the health of your orchard.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

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