Diseased Maple Trees

Asked October 22, 2019, 2:07 PM EDT

Our community has a number of maple trees that are struggling. We have dozens of these trees in the neighborhood, and most are fine, but we're concerned this may spread. We're in the process of changing landscaping companies, and the companies have given us various opinions of what this is and whether the trees can be saved. The branches are drooping, and the leaves are sparse on these trees. The trunks have splits in the bark, and some have green, mossy growths. Can you tell us what this is and what you would recommend if the trees can be saved? Also, is there any preventive measure we can take to keep this from spreading to other trees in the neighborhood?

Howard County Maryland

3 Responses

Without being on-site, diagnosing a whole neighborhood of trees isn't possible.
It is not likely however that a disease is causing most of the issues.
More likely are what we would term 'abiotic issues', that is, problems not related to disease or pests, but that are related to cultural or environmental factors.
This could include poor planting techniques and/or care.
For instance, we often see trees planted or mulched too deeply. You should be able to see the gentle widening/flare at the base of the trunk. It shouldn't go into the ground straight like a telephone pole. Mulch should be no deeper than 2-4 inches (NOT mulch volcanoes) and shouldn't be in direct contact with the bark. Too much soil/mulch over the roots suffocates and kills the trees over a long period of time, proceeding with a slow decline.
Maples often develop girdling roots as well, which happens when circling roots in the pot or root ball are not spread out or cut. They continue to circle and when the trunk grows into it over time, it can limit the tree's ability to take up water and nutrients.
More of these issues are posted here: https://www.extension.umd.edu/hgic/topics/cultural-and-environmental-0

You will see too a photo and link to lichens, which are the green mossy growths you mention. In this case, the news is good, because they are natural, harmless to the tree, and can be a sign of good air quality.

The tree you show in your photo does not look terrible. Fall is a difficult time to gauge tree health. Any trees that are valuable to you or your neighbors should be monitored for changes and watered any time we don't get an inch of rain a week. (We don't usually recommend fertilizer for mature trees but if you fertilize your lawn you are also giving some to your trees as well).
This page help people better understand tree issues and when it may be time to remove a tree: https://www.extension.umd.edu/hgic/topics/how-do-you-decide-when-remove-tree

A certified arborist is a tree health expert that is credentialed by the International Society of Arboriculture (ISA). Not just a tree cutter or lawn/landscape service. Most large tree companies have one on staff and they are the ones who can best evaluate individual trees and suggest what to do. Some have specialized equipment, like an air spade, which may be used to expose the root collar (flare) of trees planted or mulched too deeply.
You can search for one at www.treesaregood.org


Thank you so much! This is very helpful information to have. We are an over-55 community with limited resources for landscaping, and we've been telling our landscaper for years that we think they are putting down too much mulch. The pictures I sent you are of the worst tree in the neighborhood, so it's good to know it doesn't look as bad as we might have thought.

We really appreciate the information, which we'll use when we've engaged a new landscaping company if they have an arborist on staff. If not, then we'll look for one at the link you gave us.

We are happy to help!
Old habits are hard to break. It makes me a little crazy how often we see huge mulch volcanoes around beautiful trees, often put down by professionals.

Take a look at this page from Penn State and you can share it later: