Oak tree brown spots/ leaf desth - Ask Extension
12 year old oak. This spring brown spots on leaves and new growth leaves shriveled and dead
Knowledgebase
Oak tree brown spots/ leaf desth #869387
Asked May 20, 2024, 11:38 PM EDT
12 year old oak. This spring brown spots on leaves and new growth leaves shriveled and dead
Summit County Ohio
Expert Response
Thank you for asking Extension about your oak problem. First, a couple of questions for you--
This appears to be in the red oak family. Do you know what type?
Are any other trees in the vicinity affected?
Are there any other trees like this one that are unaffected?
Has there been any pesticide/herbicide use in the area that may have drifted?
Has your weather been cool and damp? Or dryer and hot (for May)?
Are there any raised lesions on the top or underside of the leaf? These could be caused by insects laying eggs in the leaves or causing leaf galls to form.
Have you seen any small larva (about 1/4" long) on the leaves or between the upper and lower surfaces of the leaves?
From your photos, there appears to be some damage from the Oak Shothole leaf Miner (see second link below). This is common and self limiting, and shows up about this time of year. The leafminer (a small fly) causes the holes but not necessarily the blotchy brown spots.
Brown spots on leaves are often caused by fungi, commonly anthracnose in the case of oaks. Many fungal diseases are host-specific and will only affect trees in the same family--that is, the fungus that causes brown spots in red oaks will probably not cause it in maples. Rusts are another type of fungal disease that cause leaf discoloration and damage, but they are usually characterized by raised orangish-brown "pustules". I don't see those in your pictures.
Neither shothole leaf miners or anthracnose generally cause significant damage to a tree. The lesions are visible in the spring, but the insect's life cycle (or dryer weather in the case of fungus) limit the damage and the tree will replace the leaves.
https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/oak/leavesbrownspots.html
https://content.ces.ncsu.edu/oak-shothole-leafminer
The question of unintended herbicide damage is a touchy one. While most commercial applicators are very careful with their chemicals, homeowners are often less cognizant of the potential consequences of application. If multiple plants seem to be affected, this might be something to consider.
https://extension.msstate.edu/publications/forest-environments-identifying-herbicide-damage-and-selecting-herbicides
I do not see any raised areas typical of galls, but there are a large variety of insects that cause galls in oaks and some of them can cause significant leaf damage. The article below shows an example.
https://bygl.osu.edu/node/1260
Finally, if the damage seems significant and you don't want to wait for the season to change and see if the lesions continue to spread, you can send samples to the C. Wayne Ellett Plant & Pest Diagnostic Lab at OSU. Follow the link below for information on sending samples.
https://ppdc.osu.edu/
If you have some more specific information based on the questions I asked initially, please let me know and I'll try to refine my differentials. I presume from your email address that you are a veterinarian and used to coming up with differential lists and deciding on diagnostics to run based on severity of symptoms and likelihood of treatable disease. It's much the same with plants, just different causes and diseases.
This appears to be in the red oak family. Do you know what type?
Are any other trees in the vicinity affected?
Are there any other trees like this one that are unaffected?
Has there been any pesticide/herbicide use in the area that may have drifted?
Has your weather been cool and damp? Or dryer and hot (for May)?
Are there any raised lesions on the top or underside of the leaf? These could be caused by insects laying eggs in the leaves or causing leaf galls to form.
Have you seen any small larva (about 1/4" long) on the leaves or between the upper and lower surfaces of the leaves?
From your photos, there appears to be some damage from the Oak Shothole leaf Miner (see second link below). This is common and self limiting, and shows up about this time of year. The leafminer (a small fly) causes the holes but not necessarily the blotchy brown spots.
Brown spots on leaves are often caused by fungi, commonly anthracnose in the case of oaks. Many fungal diseases are host-specific and will only affect trees in the same family--that is, the fungus that causes brown spots in red oaks will probably not cause it in maples. Rusts are another type of fungal disease that cause leaf discoloration and damage, but they are usually characterized by raised orangish-brown "pustules". I don't see those in your pictures.
Neither shothole leaf miners or anthracnose generally cause significant damage to a tree. The lesions are visible in the spring, but the insect's life cycle (or dryer weather in the case of fungus) limit the damage and the tree will replace the leaves.
https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/oak/leavesbrownspots.html
https://content.ces.ncsu.edu/oak-shothole-leafminer
The question of unintended herbicide damage is a touchy one. While most commercial applicators are very careful with their chemicals, homeowners are often less cognizant of the potential consequences of application. If multiple plants seem to be affected, this might be something to consider.
https://extension.msstate.edu/publications/forest-environments-identifying-herbicide-damage-and-selecting-herbicides
I do not see any raised areas typical of galls, but there are a large variety of insects that cause galls in oaks and some of them can cause significant leaf damage. The article below shows an example.
https://bygl.osu.edu/node/1260
Finally, if the damage seems significant and you don't want to wait for the season to change and see if the lesions continue to spread, you can send samples to the C. Wayne Ellett Plant & Pest Diagnostic Lab at OSU. Follow the link below for information on sending samples.
https://ppdc.osu.edu/
If you have some more specific information based on the questions I asked initially, please let me know and I'll try to refine my differentials. I presume from your email address that you are a veterinarian and used to coming up with differential lists and deciding on diagnostics to run based on severity of symptoms and likelihood of treatable disease. It's much the same with plants, just different causes and diseases.
