Apple Canker in your orchard: Identifying and dealing with this fungus

Apple trees can live with canker and carry on as living, producing trees, remaining good for biodiversity, wildlife and fruit. It just takes a bit of monitoring and annual pruning to keep it in check.

This week I’ve been pruning a ten year-ish old apple tree that has quite a significant problem with canker. There are many open lesions on smaller side branches, lots of spur and tip die back plus the trunk has areas that look like lesions are developing.

Pruning in winter allows you to identify the canker from the small red spores of the fungus. I ensure I remove all the branches with lesions and spores on and take them right back to the main central leader. I then prune off as many branches with dead spurs and die back as possible. It’s important to take these prunings away and burn else the spores can reinfect other branches of the same tree plus spread to other apple trees in the vicinity.

In order to stay on top of a tree that has canker ensure you prune out infected material each year to prevent it from spreading. Keep it under control and prolong the life of the trees and their productivity and therefore limit the extent to which it is affected by the fungus.

Once infected, Canker can spread throughout the tree and to other trees via small red spores in the Winter and Spring (seen in this image) and white spores via water droplets in Summer. Both can cause reinfection on other parts of the tree so remove any that you find, including all fallen leaves and burn.

Canker is common in Cornwall due to the wet weather but choosing canker resistant varieties – which Cornish varieties often are – will help to keep it at bay. Despite this though, I do know many orchards that have no canker so if you keep trees healthy, choose canker resistant varieties and keep an eye out for canker infection by conducting annual pruning, you can help to ensure it’s not something you have to deal with. But if you do find your trees have canker, don’t let it worry you too much – keep on top of it and your trees will continue to live a productive and long life.

The following images are of a Charles Ross apple tree which has had a canker infection for at least 6 years – probably much longer. It can be seen at the bottom of the trunk therefore affecting all of the tree. This also causes some die back of branches in the canopy plus lesions on side branches. Despite this, you see the huge crop of apples each year, without fail. It is true that an apple tree under stress will give a bumper crop because it wants to live on and the way to do that is to produce as much fruit, and therefore seed, as possible to give it a good chance of reproducing. This tree has been cropping like this every year so it doesn’t seem like a tree at the end of it’s life yet; it does very well considering the pressures of the canker fungus that it hosts. However, it is at a stage where I wouldn’t try to prune out the infection in the main trunk as it’s really taken over the tree, and if I did so there wouldn’t be much tree trunk left. So, limiting it’s spread via spores is the main priority by annual pruning, to ensure it doesn’t spread to other trees. Luckily there are not any other apple trees in the vicinity.

In conclusion, whilst canker can weaken and reduce the length of life of an apple tree if left unchecked, you can prevent it from taking over and control it through annual pruning pretty successfully. The fungus doesn’t stop the tree from fruiting, and it carries on growing. The downside is that if you have other apple trees you run the risk of it spreading to others trees unless you take action to stop it’s spread. You need to monitor your trees in order to spot it early if it does spread.

If you’re really brave you might like to attempt to cut out larger canker infection in tree trunks as you catch it – this involves using a knife to dig out into clean healthy wood, ensuring every bit of infected wood has been removed. The cleared wound can then be covered with sealant to ensure no further infection. A video of this process can be seen here,

How to get rid of fruit tree canker – YouTube

I’d be happy to discuss canker with you further if it’s a problem for you, as well as pruning it out each year to stop it infecting other trees in your orchard.

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