Burr oak leaf disease - Ask Extension
This summer- for first time in 16 yrs- we are seeing this leaf disease on both of our burr oaks, with the youngest one 12-14 yrs old being most affect...
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Burr oak leaf disease #464937
Asked June 24, 2018, 1:56 PM EDT
This summer- for first time in 16 yrs- we are seeing this leaf disease on both of our burr oaks, with the youngest one 12-14 yrs old being most affected (photos). We noticed that it seems to be mostly affecting the bottom half of our youngest burr oak tree, and that this condition followed the long period of rainy, wet weather. with cooler temperatures followed by high temperatures. The spots start off as round, and then coalesce with other round spots For those reasons, we wonder if this is a fungus. We would like to know what disease this is and how to treat this tree to eradicate the problem. (The smaller tree was also a target of wasp gall for a few years, in the past, so it is "weaker" in that regard.) Is there a product we can get buy to apply the treatment ourselves or should we use a commercial arborist to do this?
Denver County Colorado
Expert Response
It looks like anthracnose, a fungal disease favored by cool, wet spring weather.
It is more of an aesthetic problem than harmful unless the tree is completely defoliated year after year. If you wanted to try to control it with a fungicide, the fungicide would have to be applied prior to infection/symptoms appearing.
One thing you can do is make sure you rake up and discard fallen leaf debris this autumn so as to reduce the population of overwintering spores.
Here's an article about Oak Anthracnose from CSU Extension: http://planttalk.colostate.edu/topics/trees-shrubs-vines/1766-oak-anthracnose/
It is more of an aesthetic problem than harmful unless the tree is completely defoliated year after year. If you wanted to try to control it with a fungicide, the fungicide would have to be applied prior to infection/symptoms appearing.
One thing you can do is make sure you rake up and discard fallen leaf debris this autumn so as to reduce the population of overwintering spores.
Here's an article about Oak Anthracnose from CSU Extension: http://planttalk.colostate.edu/topics/trees-shrubs-vines/1766-oak-anthracnose/
