How to Beat Bacterial Canker on Cherry Trees

Published: June 8, 2021

"What's wrong with my cherry tree?"

That's what a neighbour asked me recently. He knew his cherry tree wasn't thriving 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 had still managed to produce some 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. Bacterial canker cherry trees | Orchard People — A cherry tree with bacterial canker on its trunk. There was little that could be done to save this tree, as the disease had spread throughout it. (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 and include sunken patches on the trunk and branches. Those sunken patches often release a sticky, gummy substance. Other symptoms of bacterial canker include branch dieback, which 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.

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How to Treat Bacterial Canker in Cherry Trees

Bacterial canker doesn't just look bad; 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 the pruning is 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. Afterwards, meticulously sterilize your pruners and move on.

Hand pruners and gardening gloves. Bacterial canker cherry trees | Orchard People — After you prune out cherry tree branches with bacterial canker, it's essential to sterilize all your pruning tools. If you do not properly disinfect your tools, you may spread the disease to other trees that you use the pruners on in the future.

What Happens When You DO NOT Prune Bacterial Canker off 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 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, as this may also be infected.

Bag it up and seal the bags. Put the remains in the garbage. 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. Bacterial canker cherry trees | Orchard People — 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. In this situation, we had to remove an entire tree, as the 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 carefully scraping the canker away from the infected spot, using a clean boxcutter as our knife. Our tree recovered and is thriving today.

Canker on the trunk of an apricot tree. Bacterial canker cherry trees | Orchard People — In the case of this apricot tree in Ben Nobleman Park Community Orchard, we were able to carefully scrape out the damaged tissue from the trunk with a clean boxcutter, right down to the deadwood in the tree. We ensured all of the diseased tissue fell onto a sheet and not onto the soil, so we could remove the pathogen from the site. The tree recovered perfectly and over the years, the wound healed.

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.

When it comes to pruning off diseased branches on fruit trees, timing is important. If we were to prune off those thick branches in the autumn, the wounds would not have time to heal before the winter.

Luckily, as trees go dormant in the winter, so do fruit tree pests and diseases. So winter is an excellent time to prune off diseased branches. To learn more about when to prune fruit trees click here.

After pruning off the diseased branches, we may also treat our trees with copper spray to help prevent the spread of the disease. You can learn all about how to prune your fruit trees and protect them from pests and diseases in my premium online fruit tree care courses.

And the moral of the story for organic fruit tree growers? It's essential to know how to recognize fruit tree diseases so you can treat them early on. And the best time to learn more is while your tree is still young and healthy!

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Susan Poizner

Director, OrchardPeople.com Fruit Tree Care Education Online

Susan Poizner is an urban orchardist in Toronto, Canada and the author of Grow Fruit Trees Fast, a fruit tree care guide designed for new growers who want to grow organic fruit trees successfully - and quickly! She is also the author of the award-winning fruit tree care book Growing Urban Orchards. Susan trains new growers worldwide through her award-winning fruit tree care training program at Orchardpeople.com and she teaches fruit production in person at Niagara College in Ontario. Susan is also the host of The Urban Forestry Radio Show and Podcast and an ISA Certified Arborist.