Pin oak leaf issues - Ask Extension
We have a ~10 year old pin oak and it has brown curling leaves. Some leaves have brown spots, some are fully brown and very few look normal. This tree...
Knowledgebase
Pin oak leaf issues #867948
Asked May 10, 2024, 7:57 PM EDT
We have a ~10 year old pin oak and it has brown curling leaves. Some leaves have brown spots, some are fully brown and very few look normal. This tree has been doing this for a few years, but it seems to have gotten worse this year. Thoughts on what this is and what we should do about it? Thanks!
Delaware County Ohio
Expert Response
Hello,
I believe the damage is caused by a leaf miner fly, possibly the Oak Shothole Leafminer. This native leaf miner fly pierces the leaf to get food in the form of sap. Many times the holes are directly across from each other on the two sides of the leaf. The holes enlarge as the leaf grows and the dead leaf tissue turns brown and falls away.
Subsequently, the larvae of the fly feed on the leaf between the top and bottom layer of the leaf epidermis, in what is called a blotch mine. That feeding also causes the leaf tissue to die. This sometimes also causes a curling of the edge of the leaf. The larvae or maggots will fall off the tree and burrow in the soil until next spring.
Populations of native leaf miner flies can vary from year to year. This may seem worse this year but that could change next year.
The leaves that I see in the pictures do not look to have an extreme amount of damage. The damage does not affect the overall health of the tree.
Another issue that causes brown spots on oak leaves is oak anthracnose. This is a fungal disease which also causes leaf tissue to die and in turn, causes brown necrotic areas on the leaves. Anthracnose normally occurs between leaf veins and does not look like little round holes. It also does not cause the leaf to delaminate, or separate into layers. But, sometimes anthracnose and the leaf miner fly can be found on the same tree.
I have listed several links below for articles containing information about the Oak Shothole Leafminer and oak anthracnose. Please read this information and use it to assess the damage to your tree.
It is difficult to be 100% accurate when diagnosing tree diseases and insects by a picture, or even by the naked eye. The most accurate diagnosis can be made by a diagnostic lab. To get a diagnosis, you would have to cut tree samples of the damaged leaves and send them to an independent lab. I have listed a link below with information about the C. Wayne Ellett Plant and Pest Diagnostic Clinic (PPDC) run by OSU. If you wish to send in samples, this article will give you information about how to take samples and send them in to the PPDC.
Please write back if you should have more questions.
Thanks for asking Ask Extension.
Betsy B. - MGV
https://bygl.osu.edu/node/1796
https://bygl.osu.edu/node/1967
https://content.ces.ncsu.edu/oak-shothole-leafminer
https://ppdc.osu.edu/
https://plants.ces.ncsu.edu/plants/quercus-palustris/
I believe the damage is caused by a leaf miner fly, possibly the Oak Shothole Leafminer. This native leaf miner fly pierces the leaf to get food in the form of sap. Many times the holes are directly across from each other on the two sides of the leaf. The holes enlarge as the leaf grows and the dead leaf tissue turns brown and falls away.
Subsequently, the larvae of the fly feed on the leaf between the top and bottom layer of the leaf epidermis, in what is called a blotch mine. That feeding also causes the leaf tissue to die. This sometimes also causes a curling of the edge of the leaf. The larvae or maggots will fall off the tree and burrow in the soil until next spring.
Populations of native leaf miner flies can vary from year to year. This may seem worse this year but that could change next year.
The leaves that I see in the pictures do not look to have an extreme amount of damage. The damage does not affect the overall health of the tree.
Another issue that causes brown spots on oak leaves is oak anthracnose. This is a fungal disease which also causes leaf tissue to die and in turn, causes brown necrotic areas on the leaves. Anthracnose normally occurs between leaf veins and does not look like little round holes. It also does not cause the leaf to delaminate, or separate into layers. But, sometimes anthracnose and the leaf miner fly can be found on the same tree.
I have listed several links below for articles containing information about the Oak Shothole Leafminer and oak anthracnose. Please read this information and use it to assess the damage to your tree.
It is difficult to be 100% accurate when diagnosing tree diseases and insects by a picture, or even by the naked eye. The most accurate diagnosis can be made by a diagnostic lab. To get a diagnosis, you would have to cut tree samples of the damaged leaves and send them to an independent lab. I have listed a link below with information about the C. Wayne Ellett Plant and Pest Diagnostic Clinic (PPDC) run by OSU. If you wish to send in samples, this article will give you information about how to take samples and send them in to the PPDC.
Please write back if you should have more questions.
Thanks for asking Ask Extension.
Betsy B. - MGV
https://bygl.osu.edu/node/1796
https://bygl.osu.edu/node/1967
https://content.ces.ncsu.edu/oak-shothole-leafminer
https://ppdc.osu.edu/
https://plants.ces.ncsu.edu/plants/quercus-palustris/
