Black Spot... defoliated and anti-fungal spray

scrawford

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Hi everyone,

It is almost July here in Los Angeles (too late in the season to repot) and I am having lots of trouble with a Chinese elm that was gifted to me in April in nursery soil.

Tree showed signs of black spot and was loosing leaves so I defoliated completely and sprayed with neem oil and anti fungal copper spray, drenched the tree. Sprayed like this for two weeks, once a week.

Tree recovered mostly and after two weeks is showing lots of new growth. However, Im on week three and these leaves shown in the palm of my hand are new leaves showing sign of black spot.... the other photo is from before I defoliated.

should I defoliate again and repot? July seems like a rough time to repot plus I just defoliated two weeks ago.

The tree is in partial sun shade and I am watering twice a week throughly.
 

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VAFisher

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I have issues with black spot on one of mine. I usually do the same thing as you - defoliate and spray the tree. That usually takes care of it for the year but it comes back the next year without fail. I always end up having to remove that first flush of leaves. I have had to defoliate more than once a couple years though. I wouldn't repot - not sure that would help with blackspot anyway. Maybe try a systemic and a dormant spray this winter.
 

Wires_Guy_wires

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For fungicides to work well, they need to be absorbed by the plant or cover the foliage in some kind of protective film.
If you rip off all the foliage and then treat.. You're treating the wood and not the sapstream that feeds the foliage.
Systemics can be absorbed through the roots, but it's faster through the foliage as well.

I would wait for a week after treating before defoliating the tree next time. This also helps prevent cross contamination; the fungus can't hide from the treatment inside the wounds or sapstream because the anti fungals will get in there, and you can monitor if the treatment was effective by seeing the progression. Without foliage that's a shot in the dark.
 

scrawford

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Thank you both for this advice - glad to know I'm not the only one having to defoliate more than once.

Interesting advice with letting the funcide get into the sapstream, will definitely try this.
 
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