If your tree has developed an unsightly wound, it could be a tree canker. Read on to learn all about tree cankers, including what causes them and how you can treat them.
To spot a tree canker, make a visual inspection of the trunk and branches in spring and early summer. Look for isolated dead patches on the bark and signs of sap oozing out. The precise appearance differs depending on the type of tree, but typically cankers appear as stains or depressed areas on the bark.
How does a tree canker form?
Cankers are very common and are essentially a sign of injury, where a wound develops a fungal or bacterial infection. When a fungus gets into the tree it can grow between the bark and internal wood, killing the bark and causing a canker to appear. Other causes for cankers can include weedkiller, insects or environmental factors.
Mid-spring is when cankers start to form, causing shoots to die back. Canker diseases often kill or weaken the limb or branch resulting in it breaking off the tree during strong winds or freezing weather.
Do cankers harm the tree?
Yes. Cankers are damaging to a wide range of trees and shrubs as they make plants susceptible to diseases caused by bacteria, fungi or insects. Both new and established trees can be affected, with healthy trees being more likely to avoid suffering serious damage from disease. Trees that have already been weakened by the weather, disease or a lack of water and nutrition are more vulnerable to developing cankers.
What are the most common tree cankers?
While tree cankers are usually associated with hardwood trees, their exact nature will depend on the trees in your area. The Cytospora canker can be found on conifers, poplars and willows, as well as fruit trees, hardwood forest trees and shrubs. The Nectria canker likes deciduous trees, such as oaks, maples, crab apples and pears. The Hypoxylon canker also affects oak trees.
Cankers on fruit trees
Young fruit trees are particularly prone to cankers and can have a tough time recovering from infections. Bacterial diseases are common in plum and cherry trees, but can also affect apricots and peaches. Look out for sunken areas of dead bark and small brown spots and holes in leaves, known as shothole, that can appear from early summer.
How to treat a tree canker
Prevention is always better than a cure, and we recommend planting native or robust types of trees which are suited to the British climate. These species should suffer less stress and will be able to handle the local environment, such as soil type and sunlight.
You can also take steps to improve the plant’s natural protection against canker disease by adopting good tree care, such as watering, feeding, mulching and pruning. Prune trees in July and August when resistance is highest, reducing the chances of infection from fungal spores.
Once you spot signs of a tree canker, remove as much fungi as possible to stop the infection from spreading. Prune in dry weather and cut at least 10cm below the canker, removing all affected areas as far as healthy wood.
Do you require tree advice?
Now you know all about tree cankers, but please feel free to contact us if you have any questions about your trees. Branching Out Tree and Garden Services are NPTC and Lantra qualified tree surgeons covering North Herts and Beds. Contact us today.