Hi there l, hope everyone is well.
I’ve noticed these black spots on the first flush on my trident maple, I’ve treated with fungicide and 2 weeks ago, should I remove the effected leaves or just leave them?
Thanks Ali
Looks like anthracnose, I’ve not dealt with this myself, but I would have thought removing the leaves would be essential to stop the spread of spores. Hopefully someone will be along with specialist knowledge.
@Silva_Naturalis thank you very much, i would hate to weaken the tree to much by removing the leaves unless it’s essential, I would say 60% of the leave have it currently.
As I say, I’ve no experience with dealing with this. If you’ve had the tree long enough to know it’s got good vigour then you should know if it can cope with the foliar reduction. I haven’t used fungicides or pesticides on my trees, but I suspect retreating with the right fungicide after removing the leaves would be effective.
The tree was purchased last October. This might be one for the Q&A, will keep an eye on new flushes and see if it’s spreading, thank you very much
Sure thing, do seek out pro advice. It could also be bacterial ( Pseudomonas syringae)
Just posted in Q&A thank you for your support
Hi Ali,
I happen to have the same issue (based on the pictures) with my trident. I also saw Ryan’s comments in the Forum QA. I wanted to ask if you will be doing anything extra besides fungus treatment? Are you changing your fertilisation, position (light/shade) etc?
Hope your tree gets well asap 
What was Ryan’s conclusion, if I may ask?
Hello @bandi, I have been moteratly fertilisezing to try and boost strength of the growth and letting it run to gain strength, I live in the UK so we don’t get very hot sunny days very often, I have been leaving it in full sun and I have it tilted on a wood block for better drainage. Hope your tree get well soon.
@Silva_Naturalis he said it was thitotheria in the roots and it needs to be repoted next year to improve the soil. Not sure if that’s spelt correctly
This tree was posted in Forum Q+A 53 if you would like to hear what Ryan said 
My problem started last year - talked to a local “expert” who said it was a lack of nutrition and I should fertilise heavily. Afterwards I saw a similar comment to Ryan’s on a forum around Christmas, so this spring I repotted the tree, cleaning out all the soil. Didn’t find any root issues.
Unfortunately the tree leafed out the same way this spring :(. The post that I read last year noted that the fungus might stay in the trunk for years (yaay).
I guess I will be doing moderate fertilising and fungus treatments for now this year, and hope for the best.
Hmm, that’s a real pain, I am no expert but I have heard that trident maples are really vulnerable to fungal desieses, I would imagine keeping them dry through out spring would make a massive differance, do you dormant spray in the winter? Might be worth bringing to a live Q+A to see what Ryan would suggest, just to be on the safe side, best wishes
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Yeah, I was thinking about that. I think he mentioned something with lime-sulphur treatments while in winter - all over the trunk. Will definitely do it (live-qa) now that you reminded me.
Right now I’m keeping the tree in my driest corner of the garden.
I done mine once the leaves dropped last year but missed it this spring, not sure if that’s made a differance or not, now that the growth has elongated the new leaves don’t have it on and are larger in size than the first leaves. Hopefully that helps
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@Ali10 ah, phytophthora. Thanks.
@Silva_Naturalis no problem 
Thought I’d leave an update with what I’ve done, and the progress.
Replanted the tree in the spring window. Washed out all the existing soil, and cut back the roots. Planted in a new pot with better drainage (i.e nr of holes) and in pure akadama.
Moved the tree in a spot with indirect sun, and some shade in the afternoon.
I removed all the leaves that looked affected (including new budding leaves, that had black spots). I basically had to do a full defoliation on a weak tree.
Besides this I applied 3-4 treatments of a Mancozeb based fungicide(in cycle of 10 days)
I only watered the tree when the soil would be dry (this would be every 2-3 days). I now water almost daily, as the summer is hot.
As a result, the tree has budded out and leafed out beautifully, and I see no fungus signs.
I still apply a spray of fungicide every month. just to be sure 
Here are some pics:
Sick tree in May (post potting)
Healthy looking tree in July:
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