Last weekend I was at a nursery that I've had good luck buying citrus from in the past. The selection was sparse this time and a lot of what was there had some sort of scale infestation I had never seen before. Each one was rather large in size, orange in color, and were on both the stems and the leaves. Some trees were so heavily infested I could see them ten feet away.

I pointed them out to the woman working there and she said there were a "friendly scale" that ate the sooty mold that developed on some of the trees and did no harm.

I know there are a lot of scale species out there that I have no familiarity with so I'm asking here if anyone knows if this is true? I sure wouldn't want to be bringing the stuff home to infest the trees I already have.

They did not look like any of the scale such as these:
http://edis.ifas.ufl.edu/pdffiles/CH/CH19500.pdf

.....Alan.

I have heard of some mites that eat other mites, but never heard of friendly scale.

I do not believe there is any such thing as "friendly" scale. ALL scale suck nutrients from the plant. I would be very wary of buying anything from this seller.

I agree with Lazz. I have never heard of any such scale, or anything else feeding on sooty mold. Scale causes sooty mold. In my opinion, the lady was into selling citrus and didn't mind using a little BS to get the job done.

Ned

This is what I'm coming to believe as well which is too bad as I've bought a number of good trees from them in the past and they often have a good selection of temperate fruits as well.

I've tried a dozen Google searches and cannot find anything about any insect that feeds on sooty mold. It would be nice if I could because my Key limes have it right now and I can't spray them because they're covered in blossoms. I sprayed them before I put them up for the winter, but it looks like they need it again.

I'm going to be a lot more cautious about their trees after this.

.....Alan.

I think the lady had her biology wrong, but likely had a valid point. You say they were orange, and there's an important point. I suspect they were Aschersonia, a fungus often called "friendly fungi," which feeds on the crawler stage of citrus whiteflies. If it manages to get rid of all the whiteflies, then the sooty mold has nothing to feed on and eventually goes away. So in the long run, she was not entirely wrong.

Have a look at web photos of Aschersonia and see if that may be what you saw. It does look remarkably like a large scale insect.

Malcolm

Here's a link to a good photo:

http://woodypest.ifas.ufl.edu/images/slide52.jpg

Malcolm

I was hoping you'd see this. That looks very much like what I saw. Some of the trees had rather a lot of the stuff too. If it eats whitefly larva I wish I'd brought some of it back with me now. White flies give me problems every winter.



Learn something new every day.

.....Alan.

Thanks Malcolm! That is certainly new to me. I spoke too soon.


Ned

It's pretty common on home dooryard citrus trees in Florida; somewhat rarer in commercial groves. For it to do well, you have to not spray any fungicides (especially copper), and you need rainy, humid weather. But under those conditions they can wipe out a population of whitefly.

Indeed. I have never heard or seen anything like it here.

Thanks, Malcolm

Very interesting, never heard that that before. However, I don't know if I wouldn't rather have a white fly problem, than all of that on my trees. - Millet

Well, they are messy looking, but quite harmless. That's "red aschersonia" (A. aleyrodis) you're seeing. It attacks the citrus whitefly as well as cloudywing whitefly, our two most common and important species of whitefly on Florida citrus. There's also a less common yellow aschersonia (A. goldiana), which feeds on cloudywing whitefly only. So sometimes we see both colors on the same leaf, if the weather is right and there are cloudywings involved. Think of it as Christmas decoration...

Then in dry weather, there is the brown whitefly fungus (Aegerita webberi) which gives some control of citrus whitefly in dry weather, and can also be mistaken for some sort of scale.

Interestingly, the woolly whitefly and the citrus blackfly are not attacked by any of these fungi, but they are adequately controlled by other insect parasites, so tend not to become a problem.

This is good timing. Yesterday was whitefly day in my citrus pest management class, so I've been talking about these guys.