The Q&A Archives: Spiny Leaves On Maple

Question: Last year my maple tree, somewhat mature, developed what looked like spines on some of it's leaves. In the fall I was very careful to remove all of the leaves that dropped and took them to the trash dump. I thought that it was caused by an insect of some sort, and removing the leaves would help. This spring, the tree looked fine, but soon the spines were back. I cut the lower branches off, which took care of some of the leaves, and got them off my property. I also took down any branches that were dead. It seems to only affect one side of the tree. The tree stands alone, so all sides get about the same amount of sunlight. Any ideas what is causing this, and how I can prevent it next year? The tree appears to be very healthy aside from this. The neighbors have an older maple about 100 yards from mine, but in a drop off. Will this have any effect? Is it a disease, or an insect? Thanks for any help you can give.

Answer: It sounds like your tree has an infestation of a gall forming insect. The structures you see are grown by the plant in response to the insect's activity. Inside are the young insects which develop into adults and then emerge from the structures. Removing the fallen leaves was a good idea.

Gall insects are seldom a major concern. They don't usually warrant spraying. Occasional outbreaks are usually brought into check by their natural enemies. The tree should releaf without any long term, detrimental effect.

It is possible that another stress such as root injury from construction or herbicide injury from lawn weed control is involved in the problem. However, based on your description, it is unlikely. If your tree is losing lots of leaves, consult an arborist. If it's just a few leaves, I wouldn't worry.

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