Pests, Fungus, or watering issue?

[DraytonSawyer]

This is the 2nd year in a row that these odd spots show up. The elm is outside in direct sun for 6 hours every day. Wiz repotted this spring although this exact issue cropped up last season prior to being repotted and the soil swapped for an inorganic substrate. It appears pest free when inspected. It's watered only when the first inch-ish of soil is dry. A decent portion of the foliage have taken on a somewhat red tint near the edges, which suggest a watering issue but adjustments seem to not help. After the slight red color appears the asymmetrical dots are not far behind as seen in the attached images.

Any help identifying what I'm dealing with here would be extremely appreciated.

 

[DraytonSawyer]

Tree was brought inside only for these few pics, fyi.

 

[Tums]

Are you fertilizing it?

 

[DraytonSawyer]

Are you fertilizing it?

Yes, it just received its first round a few weeks ago. 5/7/4 organic slow release pellets from Superfly Bonsai.

It is my first time using this particular brand. Are you thinking too much or too little?

Anyone ever see Anthracnose (black spot disease) with spots like this?

 

[Tums]

Does not really look like a leaf disease to me. I was thinking it could be some kind of nutrient deficiency if you never fertilized. Does it clear up later in the season or persist? It starts on the new growth?

 

[DraytonSawyer]

That's a relief on the disease side of things. None of my other trees are affected by it so mostly it was just being over-cautious

Appears on older growth, rarely on new. Seems to start after the new growth has hardened off.

Unfortunately, it does persist throughout the season.

It really has me vexed! I'd be thrilled if it's a simple nutrient deficiency. Maybe low on nitrogen?

also, thanks for taking a look my friend!

 

[Tums]

The red color/spotting has me thinking phosphorus. Hopefully we can get someone else's opinion since I don't consider myself an expert.

 

[DraytonSawyer]

Interesting...so the fertilizer I was using was low on the phosphorus side at 9/3/6. The new batch being 5/7/4 is higher but has just had its first application a month ago.
I stopped fertilizing once the issues started just to control my variables but I'm wondering if you might be onto something.

We're talking about a phosphorus deficiency and not an overabundance of it, right?

 

[Tums]

Yeah, I was thinking a deficiency.

 

[penumbra]

I believe it is just an older leaf that the plant is shedding. Unfortunately, Chinese Elm sometimes tend to want to hold onto its old leaves. Clip it off.

 

[Tums]

Oh, interesting. I assumed it would shed all of its leaves in a zone 5 winter, but I have only just purchased one myself so I wouldn't know.

 

[DraytonSawyer]

Appreciate the tips! Oddly enough I have one that loses all foliage in winter and another that does not.

 

[penumbra]

Appreciate the tips! Oddly enough I have one that loses all foliage in winter and another that does not.

Really not all that strange for this plant.

 

[Shibui]

There are many different cultivars of Chinese elm. Some are more deciduous and some tend to hold leaves for longer.
If this is the one that holds leaves through winter then this is almost certainly leaves dying from old age.

 

[DraytonSawyer]

Very familiar that there are two types of elms; ones that will lose their leaves and ones that will not. My issue is that this particular elm does lose all foliage when dormant. This is all growth from just this spring, although the issue appears on the older portion of this Springs growth. Far too soon for it to be dropping leaves from age or discoloring, I would think.

I am a beginner so I do appreciate all the help but All that being said; would you still consider this just older foliage dying off and normal?

I really would like to find out what this is.

 

[Shibui]

Always hard to diagnose from photos. You are in a much better position to judge whether these are last year's leaves or new season leaves.
If this is new leaves turning brown I am not familiar with the issue so cannot recommend a cure.