What’s up with your spruce tree? You planted it as a source of greenery and as a natural screen to hide your neighbor’s house and the noise from the street. Now your spruce needles are turning brown and falling off. Normally, the annual spreading of fertilizer will perk it up, but it seems to have less effect now. What’s going on?
Spruce trees are very successful temperate and boreal trees in the Northern Hemisphere. But its very popularity can be a detriment. Because it’s such a successful tree, it has more enemies: mostly, other spruce trees. If your tree is a host for a fungal disease, it could be a danger to other spruce trees or conifers in your area.
Here’s what you need to know about your spruce tree’s needles.
Keep an eye on your spruce tree in extreme weather, all year long
In recent years, the summers have been hotter. There also have been wetter wet seasons that cause flooding, and winters have been colder. These factors are major stressors for trees and can cause their needles to turn brown or even drop off. In the summer, be sure that you’re watering your tree correctly, and the correct amount. This can vary depending on the species, how much sun it’s getting, and other variables.
Pay attention to where the needles are falling from and which branches are turning brown
Cytospora canker
Depending on where that is, you might have a few different problems. If whole branches are turning brown and dropping their needles from lower on the tree, you may have a cytospora canker. This canker lives beneath the bark of the tree and destroys the vessels that transmit nutrients and water to the rest of the tree. The whole branch will dry out and die. Another symptom of this canker is a white sap on the trunk of the tree and the affected branches.
After the branches low on the tree have dried out and died, the rot will slowly move up the tree. It can take quite some time to kill the whole tree this way and usually only affects trees that are mature or at least 15 years old. Unfortunately, there’s no treatment for a cytospora canker. The tree will not be killed immediately, but it will die of it within several years.
Rhizosphaera needle cast
However, if your spruce tree has many different branches where the needles are turning yellow or brown and falling off, you may have a different fungus problem, called rhizosphaera needle cast. This fungus can kill a tree over three or four years, and it infects individual spruce needles rather than the whole branch. This fungus is most active in humidity and will most commonly come to light in the spring.
The good news is that this fungus can be managed. While the tree won’t be able to “fight it off” like a human fights off a cold, it’s possible to protect the health of the rest of the tree. Needles can also grow back from the bare patches (though that doesn’t guarantee they will).
There are fungicides you can use, and pruning away the diseased branches is an important maintenance task. It’s most helpful to prune the trees when the weather is dry since the fungus is so happy in the humidity. Pruning increases the airflow and reduces the amount of humidity trapped within the branches of the tree, so pruning will have double the effect.
So what can you do to help prevent and treat your trees?
First, keep an eye on them
Inspect them every season or so. This is a good idea to make sure that there wasn’t any damage in the previous season as well, especially if you had particularly strong winds or heavy flooding. And maybe your trees need a little maintenance anyway. Cleaning off moss and lichen, removing dead or broken branches, and inspecting old cracks to make sure they aren’t a hazard are good ways to take care of your trees.
Second, you can plant your trees a good distance from each other in the first place
If you have a large cluster of spruce trees, and one of them gets diseased, it will be much more difficult to keep the disease or fungus from spreading to the others. Planting trees too close together, no matter the species, can also stress them out because they’ll be competing for resources: water, nutrients, and sunlight.
Third, if you decide to remove one of your diseased spruce trees, it might be a good idea to replace it with a different kind of tree
This will minimize your risk of spreading disease and fungal infections in the future. Diversity and variety are natural combatants to diseases that infect only one kind of tree.
Lastly, even if your tree has a canker that can’t be saved, you can still remove unsightly dead branches
Make sure to clean your pruning shears with rubbing alcohol or another disinfectant in-between each cut. If you don’t, you might end up spreading more of the fungus spores and making your problem worse. Once the branches are cut, be sure to clean up the branches and needles from beneath your tree—they will be rife with fungus spores. Leaving them there won’t do your diseased tree or nearby healthy trees any good.
Finally, spread a good layer of mulch around the base of the trunk to protect the roots. If there hasn’t been any rain recently, give it a good watering to wash away any last traces of spores that you might have dislodged from the branches above.
If you’re unsure about which affliction might be affecting your tree, or if you’d like assistance with pruning, it’s a good idea to call in a certified arborist. You want to be sure if the issue is due to disease or to weather elements. Mr. Tree Service is happy to come take a look at your spruce tree. We have certified arborists on staff because we take your trees as seriously as you do. Contact us today!
