Brown spots on elms and linden

[Kahless]

I have recently noticed that a few of my trees have brown spots and yellowing of leaves. I see this mainly on my Siberian, elms, American Elm, and Linden. They are growing in a mixture of ocean Forest potting soil, Napa, DE, pumice, and lava rock. I’m not sure of the exact mix in these trees. It rained a lot earlier in the summer, and I water every other day or so. Is this a fungal infection? I bought some copper fungicide just in case. Should I treat with fungicide, or just repot? I know it’s the wrong time of year to repot.

 

[Kahless]

Also, I moved to a new location close to a forest with more insects, if that has any relevance.

 

[WNC Bonsai]

Looks a bit like leaf spot disease which can be fungal, bacterial, or viral infections, so pick your poison. Here’s a good online resource.

Leaf spot diseases of trees and shrubs

Leaf spots, cankers and blights caused by multiple pathogens have very similar management options.

extension.umn.edu

 

[Kahless]

So should I spray with copper fungicide? Not repot? Leave it alone? I still don’t really know what I should do so I guess I will start with the fungicide and experiment

 

[WNC Bonsai]

Did you read what it says on the UMN website? I thought they gave pretty good guidelines. Basically they say that fungicides etc. need to be used to prevent infections. If you have conditions that may result in repeated infections then fungicides may work to prevent them but once you see the spots the life cycle is probably over.

 

[Kahless]

Did you read what it says on the UMN website? I thought they gave pretty good guidelines. Basically they say that fungicides etc. need to be used to prevent infections. If you have conditions that may result in repeated infections then fungicides may work to prevent them but once you see the spots the life cycle is probably over.

Sorry, I see that now. So basically I would want to treat all of my trees while they are still looking healthy.

 

[WNC Bonsai]

Sorry, I see that now. So basically I would want to treat all of my trees while they are still looking healthy.

If your trees are likely to experience the conditions they spell out on the website that are conducive to leaf spot disease then yes I would apply a fungicide as a preventative measure.