Linden Leaves

Question: What is this on the leaves of my Linden Tree? Is there anything I should do to remedy it? This has regularly occurred over the last few years, but some years it’s worse than others. Thank you for your time.

responder: An Ask Extension Expert Replied June 20, 2023, 1:03 AM EDT
response: Thanks for the question. 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://pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/linden-tilia-linden-gall-mite - :~:text=Pest description and damage A,Damage is seldom serious.&text=Predatory mites are important biological control agents. https://horticultureforhomegardeners.ca/2021/06/21/spindle-galls-unusual-growths-on-linden-leaves-caused-by-eriophyid-mites/ https://www.torontomastergardeners.ca/askagardener/weird-stuff-on-my-linden-tree-leaves/ https://extension.umn.edu/yard-and-garden-insects/insect-and-mite-galls Thanks for the question. Get back with any questions.

responder: The Question Asker Replied June 20, 2023, 11:14 PM EDT
response: So sorry, see attached regarding below email.On Tue, Jun 20, 2023 at 10:07 PM Paul E <<personal data hidden>> wrote:Hi - thank you very much for the info. Is there a reason why they’d be on my Linden and not the neighbors on either side, both with a Linden of the same size/age?Also, another tree concern is my maple (next to my Linden). It wasn’t in great shape when we moved in 6 years ago, some dead branches mixed in throughout. It has been doing pretty well since but then last year took a turn. Last spring it came on strong and then suddenly a bunch of leaves started turning and ultimately died. What could have caused this, is there anything I should do, and will it be able to recover or will I ultimately have to cut this down? See attached picture. Thanks so much!PaulOn Tue, Jun 20, 2023 at 12:03 AM Ask Extension <<personal data hidden>> wrote:

responder: The Question Asker Replied June 20, 2023, 11:14 PM EDT
response: Hi - thank you very much for the info. Is there a reason why they’d be on my Linden and not the neighbors on either side, both with a Linden of the same size/age?Also, another tree concern is my maple (next to my Linden). It wasn’t in great shape when we moved in 6 years ago, some dead branches mixed in throughout. It has been doing pretty well since but then last year took a turn. Last spring it came on strong and then suddenly a bunch of leaves started turning and ultimately died. What could have caused this, is there anything I should do, and will it be able to recover or will I ultimately have to cut this down? See attached picture. Thanks so much!PaulOn Tue, Jun 20, 2023 at 12:03 AM Ask Extension <<personal data hidden>> wrote:

responder: An Ask Extension Expert Replied July 01, 2023, 3:03 PM EDT
response: Thanks for your response. I cannot offer any good reason as to why your linden should have these galls while your neighbor’s tree is absent of them. As I previously said these galls pose no problem to your tree. You may or may not see a recurrence of them in 2024. There are many things that might be affecting your maple. The best thing to do is to have a professional arborist make an on-site inspection and assessment. See: https://extension.umn.edu/planting-and-growing-guides/how-hire-tree-care-professional Good luck