Knowledgebase
What is going on with this tree? #885349
Asked September 15, 2024, 8:39 PM EDT
There is a linden tree in the yard that has been dropping leaves early. The leaves look like they have some black marks on them. Does this look like gall mite? Not really sure what is going on with the tree.
Ramsey County Minnesota
Expert Response
https://bugguide.net/node/view/2008703
Thank you very much for your response. It helps to know the tree is not in danger. Do you think the problem will likely be gone when the leaves return in Spring?
https://extension.umn.edu/yard-and-garden-insects/insect-and-mite-galls
Similar life cycle
https://hort.extension.wisc.edu/articles/maple-gall-mites-eriophyidae/
Here is some information from another expert from last year.
There is no worry; there is nothing you should do; your linden is still healthy. What you are observing on the leaves are called galls. They have small mite larvae within them. Here’s the deal. Last year (2022) an eriophyid mites (hard to identify the exact species) were present on your linden tree where they overwintered under pieces of bark or some other nook or cranny of the tree. This spring (2023) all these mites emerged from their hiding places and mated with one another. Eggs were laid on the emerging leaves of your linden and larvae quickly hatched. These larvae burrowed into the leaf tissue. The leaves responded by enclosing the larvae with a form of leaf cancerous growth. A type of defensive response. This led to the appearance of the bumps and nodules which you are seeing. The tree is not harmed in this process. Soon from each gall will emerge an adult mite. They are incredibly small so don’t expect to see them. These adults will spend the rest of 2023 and through the 2023-24 winter living on your tree. In spring 2024 the cycle begins all over again. See:
https://www.torontomastergardeners.ca/askagardener/weird-stuff-on-my-linden-tree-leaves/
https://extension.umn.edu/yard-and-garden-insects/insect-and-mite-galls
Thank you very much for all the very helpful information! If the gall is present in the tree in Spring, in other words remained in the tree in the winter season, how many cycles can this go on for? Is there anything we should do in Spring if that happens? I see the links mention putting an oil down in the dormant season. In the fall, we always have truegreen tree and shrub fertilization done. Do you think this might be helpful or not for this tree? Thank you again so much for all your help!
The mites will be back every year unless a weather change inhibits their reproduction. Since they don’t harm the tree it isn’t necessary to treat the tree.