Brown Spots on Trident Leaves

[sbap]

Hello All,

I am a newbie and have collected a few nursery stock junipers to practice working on - and after a couple of trips to Fuji Bonsai Nursery in Sylmar I found myself walking out with some elm trees and a trident maple.

I repotted the maple back in February and it has been doing just fine since, but over the last couple of weeks I've noted that the leaves are getting brown spots and some of the new leaves are turning dark at the tips.

I've kept it in full sun this spring as I was hoping the March/April sun wouldn't yet be too much for it, and I see to it that it is watered each day. I'm a few miles inland from the coastline here in San Diego, so the Santa Ana winds (dry/hot winds) don't too often reach me...

Could these spots be a fungus, or did I harm the tree by giving it too much sun?

Any advice or information is appreciated - Thanks!

 

[mikeTF]

There could be a few issues.
One: could be the time you are watering. The droplets act as magnifying glasses and burn leaves.
Two: Was it in leaf when you repotted? Did you give it shade for a week or two until it established?
Three: possible phoma, if so it is for the life of the tree.

 

[Kodama]

One: could be the time you are watering. The droplets act as magnifying glasses and burn leaves.

Hmmm.. I've read several things that suggest this is a myth? If true, wouldn't all trees in nature be leaf burnt after a rain, etc? Curious minds want to know.

 

[mikeTF]

Feel free to post the studies completed I would be quite interested to see. Maybe you have some advice for this enthusiast? All I have is my experience with my Trident maples and growing them out of zone in 10A. You might also notice I mentioned three things and there quite very well could be more. Such as if the tree no longer pushes growth it was likely treated with bayer etc...

 

[eugenev2]

Hmmm.. I've read several things that suggest this is a myth? If true, wouldn't all trees in nature be leaf burnt after a rain, etc? Curious minds want to know.

It's a myth. And if all conditions coule be met to make it possible, the position of some the leaves in the picture is such that the water would simply have run down the leaf yet they have these spots. The spots could be some sort of fungal issue, but the leaf burn seem to indicate either not watering enough or the temperature the tree was exposed too was too much for the tree. It could also be fertilizer related...but...
The OP's post was 8 months ago, so there might be no issue anymore

 

[sbap]

Thanks for responding to and reviving this post -

I had repotted the tree in February of 2022, so it had several months to grow before the brown spots developed. I elected to de-leaf the tree and see if the new leaves would have the same issue. The new leaves that regrew were all healthy. I think I simply let the maple get too much April San Diego sun - I kept it on a porch under a 70% shade cloth for most of this past summer and it didn't experience the same sort of leaf damage as in the pictures above.

I guess San Diego is not the best place for maples.

 

[eugenev2]

Thanks for responding to and reviving this post -

I had repotted the tree in February of 2022, so it had several months to grow before the brown spots developed. I elected to de-leaf the tree and see if the new leaves would have the same issue. The new leaves that regrew were all healthy. I think I simply let the maple get too much April San Diego sun - I kept it on a porch under a 70% shade cloth for most of this past summer and it didn't experience the same sort of leaf damage as in the pictures above.

I guess San Diego is not the best place for maples.

Good to hear, i've personally found that Japanese and trident maples start becoming a bit unhappy when the temperature goes above 25C (77F). But i wouldn't say it isn't the best place, if you can keep them within the right temperature ranges and provide them with enough water they grow like crazy. For example quick online searches indicate that trident maples are slow to medium growers, with supposedly 1 to 2 feet a year growth, but here in my climate i've cut off 2 feet of growth this season already another 2 feet has grown and we still have another 2 months of summer left.
Personally i would play around with the shade cloth percentage (if you haven't already), compare growth from one year to the next, as well as see at which percentage you start getting leave burn again, i feel like 70% might be a bit too much (but your temperatures can get a fair amount higher than mine, so could be perfect), you may be loosing out on some of your beautiful sun there, a 50% or possibly 40% might be adequate (although 40% works for me, so might not work for you)
Another thing to remember is wind, wind plays and important factor as well, as dry hot winds can impact the tree as well.

 

[ChristianDGreat]

@sbap

Most likely fungus specially the black collored foliage,
This is not sun related, you can search @Smoke post about this. He talk about anthracnose.

Thanks
Chris

 

[PeteB]

Three: possible phoma, if so it is for the life of the tree.

Hi Mike. I have 2 Trident Maple seedlings which exhibit exactly the same symptoms as your little guy. In their first year they were in a fairly shady spot and came out with the all the symptoms shown and then again this year when they had been moved to a morning full sun location before budding where they became infected again. They appear quite strong and are pushing out a second budding so I will try the two sprays you mentioned and see what happens. A progress report on how your little guy makes out would be much appreciated, I will do likewise. Thanks for your post and good luck with your little guy. Cheers Pete