Why Does My Pear Tree Have Canker on the Branches?

Canker on a pear tree presents as a clearly defined area of sunken, discoloured and often flaking bark, usually centred on a wound or old pruning cut. Left untreated, it expands in concentric rings over successive seasons until it girdles the branch — encircles it completely — causing the wood beyond it to die back. Pear canker is manageable if caught early, but requires decisive action.

What causes pear canker

Pear canker is caused by the fungus Neonectria galligena (formerly Nectria galligena). The spores are widespread in the air and in soil, particularly in wet conditions. They enter through any break in bark — pruning wounds, frost cracks, insect feeding sites and natural leaf scars where autumn-dropped leaves have left an entry point. Wet, poorly drained sites and trees growing in dense, humid conditions are most susceptible. The fungus produces concentric rings of flaking, sunken bark and small, cream or orange-coloured pustule fruiting bodies are often visible on the edge of the lesion.

How to prune out canker

Small cankers on shoots and spurs should be cut out entirely — remove the affected wood back to clean, healthy tissue. For cankers on larger branches, pare away all the diseased bark and wood down to clean tissue, leaving an oval or elliptical clean wound. There is no need to apply wound paint — research shows modern wound paints do not significantly speed healing and may trap moisture. For a branch that has been girdled more than half its circumference, removal of the branch entirely is usually the better option as the canker will complete girdling before the wound heals. Sterilise tools before and after each cut.

Prevention through site and management

Improving drainage around the roots significantly reduces canker pressure — the fungus is far more active in persistently wet conditions. Prune in dry weather, preferably in midsummer when the cambium is most actively growing and wounds heal fastest. Avoid heavy autumn pruning that leaves fresh wounds heading into wet winter conditions. Make all cuts clean and smooth — tearing or crushing the wood around a cut creates the ragged wound edges that canker colonises most readily.

Canker-resistant varieties

Some pear varieties show greater canker resistance than others. Conference is notably susceptible in wet conditions. If canker is a persistent and serious problem despite good management, planting a more resistant variety in a future replanting is worth considering.