Bacterial canker on a cherry tree.

Bacterial canker on a cherry tree.

“What’s wrong with my cherry tree?”

That’s what a client said to me recently. They knew their 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.

Canker – both bacterial and fungal – 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.

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 big liability and really should be cut down. Then dig out it’s root system. 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.

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.

That was last year. 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 and it’s October, and not a good time to prune fruit trees which are approaching dormancy. 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 the pests and diseases that they grapple with. 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 Beginner Fruit Tree Care Online Training.

How have you dealt with canker in your fruit trees? I’d love to hear from you!

Susan Poizner is a writer, filmmaker, and urban orchardist. She is the author of the award-winning fruit tree care book “Growing Urban Orchards”. She is also the creator of the online fruit tree care training website