Graham Mango Tree Help Please!

[Jani]

Hello all,

I've been a long time reader of this wonderful site, and without knowing, you all have helped me so much more than you know with taking care of my fruit trees. Thank you!

Well I have an issue with my beloved 3 or 4 year old potted Graham Mango tree that has made me register and submit this, my first post. I hope you can help me solve this problem. 

This afternoon I noticed that some of the canopy leaves of the tree had some red rust-like blotches on them, the blotches appeared to be on the up-surface on the leaf more than the underside. The tree gets a lot of TLC (probably way too much) and daily inspections,  so it's almost as though they popped up since yesterday or I would have noticed them before.    Otherwise the tree seems pretty healthy and is in the midst of a pretty impressive growth flush (3rd one for the summer), and the new growth seems unaffected by this condition so far.

Now here's a little background on my practices for this tree.... I've become a religious neem-oiler, ever since having been working out of town for 6 months and returning to this potted Graham and my potted Glenn almost fully covered in black mold and scale. After a couple weeks of leaf by leaf and stem by stem cleaning with insecticide soap and neem oil, I got that problem under control, and since then am addicted to weekly neem spraying.

The thing is now, I've just become so habitual with it, and I have to admit unfortunately, I just kind of wing it with how often I spray and how I mix the mixture from concentrate (don't judge me .  We've had some very very hot and bright days here in South Florida this week (and I neemed yesterday morning and didn't get rain in my location), so I'm wondering if this is neem oil burn, especially as the spots seem limited to the upper side of a few of the leaves in the canopy?

Or maybe that's what I am hoping it is and not a fungus infection/rust etc?  To me it appears to be physical damage to the leaves, and they are not covered in anything powdery that comes off if I rub my fingers on them. It seems intuitive to me that it probably isn't fungus because of regular spraying with neem? And also the sudden (seemingly one day) onset of the spots? Or am I just wishfully hoping again?

Sorry for the long-winded story but here are some pics of the situation.  Could any of you give your thoughts on what it may be, what permanent damage may result, and how this can be treated?

It would be greatly appreciated.

Thanks so much.

1. 6ft potted Graham Mango tree (against wall):


2. Upper surface of an affected leaf:


3. Lower surface of an affected leaf:


4. Distribution of "rust" spots in canopy (look closely):

[michsu]

Could it be sunburn then? You said you had a lot of hot days (like us here in CA).. If it hasn't happened because of your fertilizing, then the fertilizer isn't the fault.. that's what i think    and for the leaves, I don't really think you can 'recover' from the sunburn.. the leaf won't grow back that part if it gets rusted/burned.. the plant will just grow another leaf in its place if you cut it off..

[Jani]

Thank you Michsu, I'm leaning towards some type of leaf burning from having the neem oil "cook" on it for a blistering 92 degrees, bright sun I had all day yesterday with no rain.  At least I hope so, and that it's not fungus or disease . I wonder if I should get a chemical fungicide just in case? I really try to limit non-organic applications if I can though.

[demingcr]

It does look like leaf burn from sun or temperature exposure. Suppose it could be from salts. Either way it should be fine, the tree looks healthy. Suggest not spraying neem weekly if no symptoms are present for scale. No reason to if nothing is there.

[SWRancher]

That looks like leaf burn from the oil. Stop using Neem oil or any other oil for that matter completely during the Florida summer and if you must use it at all then only do so when its cool outside such as over the winter. Mango trees are a very tough plant a few leaves with sooty mold on them wont hurt or kill it. Best way to get rid of the soot itself is to kill the bugs causing it, usually sugar ants or white fly. I suggest you try placing an ant bait for sugar eating ants near the tree and also check that the tree is not under or near a white fly infested palm or coconut.         

[Jani]

Thank you all for the feedback.