Maple Tree disease/issue - Ask Extension
I have a maple tree in my backyard that has some dead branches and a dead leader. The leaves are also covered in red bumps, that I thought were spider...
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Maple Tree disease/issue #934957
Asked June 10, 2026, 10:09 AM EDT
I have a maple tree in my backyard that has some dead branches and a dead leader. The leaves are also covered in red bumps, that I thought were spider mites but now believe it is something else. I have sprayed the tree (last year) with Seven, but it didn’t help. I also used BioAdvanced tree protect and feed (last July) and the tree still did not have any changes in the leaves. This spring I have noticed that more of the tree is dead in the back middle. Are there any suggestions on what to do to save my tree?
Thank you!
Union County Ohio
Expert Response
Hi Stephen,
The warty red bumps that you see on the leaves of your maple tree are maple bladder galls. They are caused by a species of eriophyid mite called Vasates quadripedes. When the mites feed on the developing maple leaves in spring, the leaf tissue forms a protective blister, or gall, around the insect and that is where the insect lives for part of its life cycle. You can read more about these mites at this link: https://hort.extension.wisc.edu/articles/maple-gall-mites-eriophyidae/ and here: https://extension.psu.edu/leaf-galls-on-maple.
Because the mites are sealed up inside the galls, there is no good way to treat with pesticides. For a mature tree, these galls are just a cosmetic issue and really do not harm the tree. On a young or newly-planted tree, the galls are more of a problem, since a heavy infestation can interfere with how much food the leaves can make for the tree. You can handpick the worst of the leaves and dispose of them in the trash (do not compost them to limit the spread of the mites). At the end of the season you can also clean up the falling leaves and dispose of them. However, the mite will overwinter on the tree bark, so there is no way to complete eliminate the infestation.
You can help this tree handle the infestation by providing regular watering when the soil is dry. You might also clear the mulch away from the trunk enough to reveal the trunk flare, as described here: https://bygl.osu.edu/node/2639.
You mentioned that the leader has died. In order for the tree to continue to have good structure, a new "leader" could potentially be encouraged, but for that I would advise you to consider consulting an ISA-certified arborist. To find one near you, check the directory at https://certificates.directory.isa-arbor.com/.
I hope this information is helpful, and please contact us if you have any further questions.
Best,
The warty red bumps that you see on the leaves of your maple tree are maple bladder galls. They are caused by a species of eriophyid mite called Vasates quadripedes. When the mites feed on the developing maple leaves in spring, the leaf tissue forms a protective blister, or gall, around the insect and that is where the insect lives for part of its life cycle. You can read more about these mites at this link: https://hort.extension.wisc.edu/articles/maple-gall-mites-eriophyidae/ and here: https://extension.psu.edu/leaf-galls-on-maple.
Because the mites are sealed up inside the galls, there is no good way to treat with pesticides. For a mature tree, these galls are just a cosmetic issue and really do not harm the tree. On a young or newly-planted tree, the galls are more of a problem, since a heavy infestation can interfere with how much food the leaves can make for the tree. You can handpick the worst of the leaves and dispose of them in the trash (do not compost them to limit the spread of the mites). At the end of the season you can also clean up the falling leaves and dispose of them. However, the mite will overwinter on the tree bark, so there is no way to complete eliminate the infestation.
You can help this tree handle the infestation by providing regular watering when the soil is dry. You might also clear the mulch away from the trunk enough to reveal the trunk flare, as described here: https://bygl.osu.edu/node/2639.
You mentioned that the leader has died. In order for the tree to continue to have good structure, a new "leader" could potentially be encouraged, but for that I would advise you to consider consulting an ISA-certified arborist. To find one near you, check the directory at https://certificates.directory.isa-arbor.com/.
I hope this information is helpful, and please contact us if you have any further questions.
Best,
