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New tree - disease?!

Posted by rugbyroll AZ (My Page) on
Tue, May 24, 11 at 23:15

We just planted a new jacaranda just over a month ago. We got a 36" box, so it's big already, probably about 12 feet. It's been doing well. Per my landscaper's instructions, we've watered it almost every day for the first month and are watering several times a week now. It is only watered at the soil, not by spraying the tree or anything. There's been a good bit of new growth on the tree in that time, especially towards the top. And lots of budding in general.

I noticed yesterday though that the leaves on the lower branches of the trees have black spots on the undersides of the leaves. They are tiny, about a millimeter in diameter, and some of them have a white ring around the black spot. They seem to be a little raised. And there are many of them, all over the undersides of the leaves. I've noticed too that these leaves generally seem much less healthy than the ones towards the middle and top of the tree... drier and more brittle and less green. But nothing you'd immediately notice if you weren't right up on it.

Does anyway know what this is?? I've looked all over the web trying to find out what it is. I'm guessing it's some sort of fungus. But I can't find anything that looks exactly like it and I have no idea what I should do to fix it.

Anyone have experience with this before?? Thanks!

Follow-Up Postings:

RE: New tree - disease?!

Here's a photo, btw...

RE: New tree - disease?!

So, most people seemed to be stumped by this, as I'm guessing people here were as well. But in case anyone else runs into this problem, here's what I've found out:

The best guess from my nursery and from a gardener friend in the UK is that this is a form of scab.

I bought some Fertilome with Neem per the nursery's suggestion.

And my friend suggested pruning all the infected leaves possible as he thought the fungicide/insecticide might not penetrate through the outer shell. So I did a heavy pruning and then treated the entire tree from top to bottom with the Fertilome. The fungicide is really just to prevent the spread to new growth. Apparently there's not much that could have been done for the infected leaves/branches anyway. Will update in a week or so to see how it turns out.

RE: New tree - disease?!

wow , very interesting!

RE: New tree - disease?!

Interesting! Thanks for the pic and for the follow up. Let us know if you decide 100% on a diagnosis. Scale sure seems likely as the spots are such a consistant size, but it's hard to say. A fungicide probably wouldn't kill them if they're insects, but I'm sure there are plenty of insecticides out that there would kill them, IF you even decide to go that route.

Do keep us posted and good luck!

RE: New tree - disease?!

Thanks guys! Well, I've got an update. I had put an email in to the Desert Botanical Gardens and they finally got back to me. They think, and I think they're right, that it is a species closely related to the Acacia White Fly Nymph. I took a "sample" into my lab today and took some 60x mag photos.

They did say that it won't kill the tree. But they might kill all the leaves. And essentially that I should be happy to have such an uncommon, educational visitor. :o) In so many words anyway.

Ok, here's the pics:


Oh, and here's a link for some additional info on whiteflies and cross referencing photos:

Here is a link that might be useful: Acacia Whiteflies in the Low Desert

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