Cytospora Canker on Spruce Trees


We don’t have a lot of evergreens up here on the hill. The wind seems to dry them out and kill them before they live all that long, so I appreciated it when a local gentleman contacted me about an issue he has with his 60-year-old spruce.

He said this winter he noticed that it looked like it had white flour sprinkled on it, so he took a sample to the extension office and to a local tree company. Eventually they came up with: it was some sort of fungus. The tree company said they needed to do an injection protocol on it in order to save it. I’m grateful that he called me before giving them the go ahead. When he described it to me, it sounded like a fungal issue, too, but since trees aren’t my specialty I called our very knowledgeable city forester.

It’s always nice to be able to contact people who are far more versed in these areas. He had me bring in a sample and identified it immediately: Cytospora canker.

Identifying and treating Cytospora canker

Cytospora canker is a fungal disease caused by Leucostona kunzei, and is prevalent in spruce trees. Initial indications that something is wrong are often evident because of dying branches. The cankers on the trunk and branches ooze and the resin becomes white, or sometimes a blueish white. It can drip down to the other branches, so I can see why he thought it looked like flour was dumped on it.

The good news is he doesn’t have to pay a tree company to do fancy injections because it won’t do it a lick of good. (It’s a peeve of mine that these companies take advantage of people like this.) The bad news is it can be devastating to the tree. The best thing he can do now is to trim out the affected branches, being sure to disinfect his tools after every cut, and to provide plenty of water to the tree.

One factor in a tree becoming infected is it being stressed by environmental factors. Of course, looking back over a year ago to the crazy (extremely warm to sub-zero) temperature fluctuations in the fall, to a predominantly dry year, it’s no surprise the tree was susceptible to infection. The dry season this winter isn’t helping matters at all, so watering the tree is necessary if he wants any chance of saving it. However, the city forester also pointed out that it was imperative not to apply a heavy nitrogen fertilizer as it exacerbates the issue. I’m glad he mentioned it because, personally, that would be a direction I would go: I would want to provide plenty of nutrition to a tree in trouble. In this case, it would only make it worse.

I learned a lot about canker this week. So if your spruce tree branches look like they got in a flour fight, prune judiciously, water abundantly, and don’t pay someone for a treatment that won’t do a thing.

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