Is this powdery mildew on tree leaves?

doginthegardenAugust 15, 2012

I'd appreciate some help diagnosing an issue, and would appreciate suggestions for dealing with it. I am in the hot and dry San Fernando Valley. I have a large shrubby tree, maybe a ficus? that has an infestation of......something. It has a grey webby/powdery substance all over the front and back of the leaves. I've been reading up on powdery mold, and it has some characteristics that seems like this is the issue, powdery and if I disturb the branches the white stuff flies off like a very fine dust, and makes me run for a dust mask before I breathe in the junk. However it also looks a lot like spider webbing on and between the leaves, which does not seem to be a characteristic of powdery mildew. There are no spiders or bugs visible. And it has not been humid here much this summer, just hot, and that appears to be a precondition for powdery mildew.

Any ideas? I'll try to add a photo in this post and/or in the link line.

Thanks so much.

Here is a link that might be useful:

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hoovb zone 9 sunset 23

That looks like a whitefly infestation. Are there little white bugs flying around when the foliage is disturbed?

    Bookmark   August 15, 2012 at 4:45PM
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hosenemesis(SoCal Sunset 19 USDA 8b)

It looks like whiteflies to me too. Sometimes they leave little circular patterns of the white stuff. When I get them, I cut off the affected foliage if it won't be too noticeable, scrape up the leaf litter, and water in worm castings. I don't know if the worm castings are hocus pocus or if there's a chemical in them that the whiteflies find distasteful, but I eradicated them from my canna lilies. It may have been just removing them physically that did it.

    Bookmark   August 15, 2012 at 11:30PM
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This is easy to treat: blast hose water on top and bottom of leaves. Do you see white concentric circes? That is the stage of whitefly you need to blast (hard) with water. It breaks the cycle. If you do cut off infected leaves/branches, bag them up so the whitefly doesn't get spread around.

I once had an entire tree covered in this stuff. Everybody said cut it down, but simple water blasting saved it.

    Bookmark   August 16, 2012 at 12:52AM
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I poked around the tree today looking for whiteflies, none around. And the castings didn't strike me as round, but I wasn't looking for that so I'll look again. You guys have me hoping it's this easy...

I'm kind of suspecting glassy winged sharpshooter, as I came across a photo on the UC pest site, and realized that I've noticed (something very much like) them lately on an adjacent pomegranate. The sharpshooters also leave a white residue but I'm not sure it's a match to the heavy webby dust all over my tree. I'll look for their eggs and the scars the eggs leave on the leaves, tomorrow. If they are sharpshooters it seems like targeting them with wasps is recommended. Hmm that might make it time to call the arborist for a visit.

Here is a link that might be useful: UC Davis Glassy-winged Sharpshooter

    Bookmark   August 16, 2012 at 3:39AM
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You may have sharpshooters too, but that sure looks like a whitefly infestation to me.

    Bookmark   August 16, 2012 at 3:03PM
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hosenemesis(SoCal Sunset 19 USDA 8b)

sbmw, the concentric circles are white, laid on the leaves, and they are the eggs of the whiteflies. Worm castings are a fertilizer (worm poop) that supposedly helps plants recover from a whitefly infestation. Here's a link to the concentric circles we are talking about.

Here is a link that might be useful:

    Bookmark   August 17, 2012 at 1:21AM
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Thanks for the feedback. The spiral photo was helpful in my understanding what was meant. And I don't see anything like it on the tree. I took a better look and some of the worse-off leaves are dappled with white spots below the fuzzy white stuff that flies off so easily, and the tips of those leaves are burnt. I tried to take some photos but my cell phone delivered fairly fuzzy shots.

I have not seen a single whitefly and no eggs visible to my eye. Just a stormcloud of white dusty stuff that is airborne when I disturb the leaves.

On the Pomegranate tree right next to it, the bugs look less like sharpshooters than I thought. Whatever they are, they are angry looking and they like pomegranate. Again with the fuzzy photos:

I like the idea of hosing it all off and seeing if that's enough.

    Bookmark   August 17, 2012 at 3:42AM
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hosenemesis(SoCal Sunset 19 USDA 8b)

The insects are unrelated to the white stuff. It's hard to tell, but those could be assassin bugs. Some have a very, very painful bite.

I think it's a good idea to try to hose it all off.

    Bookmark   August 18, 2012 at 2:32AM
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hosenemesis(SoCal Sunset 19 USDA 8b)

Found your bug. They are leaf-footed plant bugs, pests of pomegranate trees. They bore holes in the fruit, ruining it. I would squish all of the ones you can find.
Good luck.

Here is a link that might be useful: Leaf-footed Plant Bug on Pomegranate

    Bookmark   August 19, 2012 at 2:38AM
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Renee, you rock. Thanks for chasing that bug info down. Yet another critter in the yard to deal with. But at least it's not the ominously-named Assassin Bug! Gotta look that one up.

    Bookmark   August 19, 2012 at 2:22PM
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jean001a(Portland OR 7b)

Assassin bugs are beneficial in that they "assassinate" other insects, thereby helping you manage the pesky fellows.

    Bookmark   August 20, 2012 at 12:38AM
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