Apple canker

Apple canker is a fungal disease that produces often deep sunken dead areas on the branches and stems of apple – including ornamental crab apples – and, sometimes, Sorbus trees.

Cankers start off as round or oval areas, but soon become larger and irregular in shape.
Infection usually occurs through existing damage and wounds caused by other things, including pruning cuts, cold and frost damage, apple scab disease and woolly aphid attack.

As the disease develops, the canker may either get larger or heal over, but will remain active. Once it spreads to girdle the branch or stem, that part of the tree dies.
The fruit may also be affected, which starts to rot on the tree and then falls prematurely.

• Apples
• Crab apples
• Sorbus

Apple canker is caused by the fungus Neonectria ditissima. This produces spores within the cankerous lesions during summer, which spread in water to other parts of the tree.

Airborne spores are produced in winter and spring, spreading the disease further within the tree and to other trees growing close by.

Try to keep trees growing as strongly as possible to help them fend off disease attacks. However, when outbreaks of apple canker occur, this may not prevent it. Early identification of affected stems and branches is essential.

Prune out any infected growth as soon as you see it, cutting back to healthy, green, unaffected wood. Dispose of the prunings, either by burning or put them in the council’s green waste bin. Don’t leave dead wood lying around.

Pick up and dispose of affected fruit.

Ideally, as moisture and rain aids in the dispersal of spores, aim to prune in dry weather. Always prune back to growth points or leaf nodes (joints) and cut large branches just beyond the collar (the ring of swelling around the base of branches). This ensures the pruning wounds heal the most quickly.

Unfortunately, there are no fungicides available to control apple canker on fruit trees.

You can help protect new growth and prevent the disease – and to a slightly lesser extent, control existing diseases – on ornamental crab apples and Sorbus by spraying with a good garden fungicide, such as Bayer Garden Fungus Fighter or FungusClear Ultra. This is usually only practical on small trees, as you need to spray the entire tree.

Applying Vitax Medo (a wound paint) over cut surfaces, especially during damp weather or if infection is known to be present, may help prevent infection. But don’t use wound paints as a matter of routine, as they interfere with the plant’s natural healing processes and can provide a more suitable environment for fungal and bacterial rots to proliferate.

Use plant protection products safely. Always read the label and product information before use. Plants in flower should not be sprayed due to possible danger to pollinating insects. Either spray early in the morning or late in the evening when pollinating insects are less likely to be active.

Keep plants growing as strongly as possible to reduce stress. This may include watering during very dry weather and feeding regularly.

Apple canker tends to be worse in wet, heavy clay and/or acidic soils. Prepare the soil well before planting to ensure good drainage, and raise the soil pH by adding lime if necessary.

Some apple varieties have some resistance to apple canker. These include ‘D’Arcy Spice’, ‘Grenadier’, ‘Katy’, ‘Lane’s Prince Albert’, ‘Lord Derby’, ‘Newton Wonder’, ‘Reverend W. Wilkes’ and ‘Winston’.

• Secateurs
• Vitax Medo

• Apple scab and pear scab
• Bacterial diseases
• Powdery mildews
• Rust diseases
• Virus diseases