Your Guide to Easy Fruit Tree Care

How are Your Cherry Trees? How to Beat Bacterial Canker

"What's wrong with my cherry tree?"

That's what a client said to me recently. He knew his cherry tree wasn't doing too well and wanted me to have a look. One glance and I knew there was a problem. A big one. Goop was oozing out of all sorts of nooks and crannies in the cherry tree, even though the poor thing has still managed to push out some tasty cherries.

This was, sadly, the tree's swan song. That's because the owners had waited too long to treat the symptoms of bacterial canker in their beloved cherry tree.

Bacterial Canker on the trunk of a cherry tree
A cherry tree that has bacterial canker on its trunk. There was little that could be done to save this tree as the bacterial canker had spread throughout the tree. Photo credit: OrchardPeople.com.

What is Bacterial Canker in Cherry Trees?

Bacterial canker is a disease that affects cherry, plum and other related fruit trees. The symptoms can be wide ranging including sunken patches on the trunk and branches. Those sunken patches often release a sticky, gummy substance.

Other symptoms of bacterial canker include branch dieback. That occurs when the new shoots at the ends of the tree's branches die suddenly.

Affected trees may also have brown spots on the leaves. When the dead tissue in the centre of the spot falls away, it leaves an empty hole. This is referred to as "shothole" because it looks like tiny pellets were shot through the cherry tree's leaves.

How to Treat Bacterial Canker in Cherry Trees

Bacterial canker looks bad, but it can also take a toll on the health of your tree so it needs to be controlled. Luckily bacterial canker can easily be pruned out of a tree if it's done correctly.

Snip off the diseased branch and dispose of it in a sealed bag in your garbage. Do not not put it in the compost where the canker can continue to spread. Then you meticulously sterilize your pruners and move on.

Hand pruners and gardening gloves used to prune out bacterial canker in cherry tree
After you prune out cherry tree branches that have bacterial canker, it's essential to sterilize all your pruning tools. If you do not properly disinfect your tools, there is a danger of spreading the disease to other trees that you will be using the pruners on in the future.

What Happens When You DO NOT treat Bacterial Canker on Your Fruit Tree?

Pruning works when you catch the problem early on. But when you leave canker on your tree, it will continue to spread from branch to branch and from tree to tree in your community.

If you let things go too far, and canker is oozing out of the trunk of the tree and off of all of the branches, this tree can be a liability and should be cut down. After you cut down the tree, dig out it's root system which may also be infected.

Bag it up and seal the bags. Put the remains in the garbage. And start again next year with a new tree and in a new hole since some of the canker may survive in the soil where the diseased tree once was.

Plastic garbage bags containing cherry tree branches that were infected with bacterial canker.
If you find bacterial canker on your cherry tree, prune out the diseased branches, bag them up and remove them from the site. Do not put them in your compost pile as the canker can easily spread from there to nearby trees. In this situation, we had to remove an entire tree as the bacterial canker had spread around the tree and through the trunk and roots.

Examples of the Successful Treatment of Bacterial Canker in Apricot Trees

There are times when you can save a tree that has canker in its trunk - that is when it just has a small spot of canker. We successfully treated an apricot tree in Ben Nobleman Park Community Orchard by scraping the canker away carefully on the infected spot with a clean boxcutter as our knife. Our tree recovered and is thriving today.

Canker on the trunk of an apricot tree
Canker on the trunk of an apricot tree in Ben Nobleman Park Community Orchard. In this case we were able to carefully scrape out the damaged tissue with a clean boxcutter (exact-o-knife), scraping right down to the deadwood in the tree. We ensured all of the diseased tissue fell onto a sheet and not onto the soil. That way we could remove the pathogen from the site. The tree recovered perfectly and over the years that wound healed.

Now this year canker has reared its ugly head again elsewhere - in our park's two oldest and most beautiful cherry trees. It has hit a number of the tree's thicker limbs. it's October, and not a good time to prune fruit trees which are approaching dormancy. Learn when to prune fruit trees here. 

If we were to prune off those thick branches now, the wounds would not have time to heal before the winter. Luckily, while trees go dormant in the winter, so do fruit tree pests and diseases. So we will prune off those branches next spring and also treat our trees with copper spray to help prevent the spread of the disease.

It all goes to show - it's essential to be able to recognize pest and disease problems early on, while your tree is still mostly healthy. You can learn how in my Online, Self-Study Certificate in Fruit Tree Care.


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Susan Poizner

Director, OrchardPeople.com Fruit Tree Care Education Online

Susan Poizner is an urban orchardist and the author of the award-winning fruit tree care book Growing Urban Orchards. She is the creator of the award-winning online fruit tree care training program at www.orchardpeople.com and the host of The Urban Forestry Radio Show and Podcast.  She is also an ISA Certified Arborist..

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