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What is this sooty black mold on my crepe myrtles?

alameda/zone 8/East Texas

last year

This year I have been seeing alot of this black sooty mold on many of my crepe myrtles. Have not seen it this bad before. Can anyone tell me what it is and how to get rid of it?

Thanks........

Judith

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Comments (5)

gardengal48 (PNW Z8/9)
last year
It is exactly that - black sooty mold. Sooty mold is a fungus that grows on the excrement (known as honeydew) of sucking insects like aphids or scale. It is relatively harmless to the plants it appears on unless a very heavy infestation that affects photosynthesis.

Although they may be long gone by now, you need to check your crapes for insect problems and address those first. Without the presence of sucking insects leaving their honeydew, there would be no sooty mold. The mold can be washed off with some effort and does disappear with repeated rains.
alameda/zone 8/East Texas
Original Author
last year
Hard to see insects - but apparently they are there. What can I spray to kill what insects are there?
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It's Black Sooty Mold, a simple fungus that feeds on the sweet excrement of certain sap-sucking insects. In the case of crApe myrtles, the culprit is likely to be aphids. The treatment involves keeping your eye out for the insects that are infesting your plant, and keeping them under control from the very beginning. Aphids can be washed off with strong streams of water from the hose on a regular basis. Insecticidal soap works well to manage them, as well. An application or two of horticultural oil over the winter (after the leaves have dropped) will smother the eggs that the aphids have deposited in the nooks and crannies along the twigs and stems. I've found that to be a very important step in preventing a major aphid infestation. Once the insects are checked, the Black Sooty Mold will go away on its own, as the food source is gone.
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gardengal48 (PNW Z8/9)
last year
Insect problems tend to fluctuate seasonally. And the sooty mold does take some time to develop. So you may very well not see any insects present currently. Before you can spray or otherwise treat for the insects, you need to confirm what they are. Aphids are relatively easy to treat; scale less so and with proper timing required.

Can you post any clear photos showing any insects that are present now?
alameda/zone 8/East Texas thanked gardengal48 (PNW Z8/9)
alameda/zone 8/East Texas
Original Author
last year
Not really - I dont see any. I might call my local Tx A&M Forestry guy and have him come take a look. I know what aphids look like but I cant find any evidence of anything but the mold. By the way gardengal..........I always enjoy your comments on clematis!!
gardengal48 (PNW Z8/9)
last year
" I know what aphids look like but I cant find any evidence of anything but the mold "

And that's not entirely unexpected :-) Scale is a year round issue and would be obvious if present. But aphids and whiteflies, etc. are much more transitory and certainly less active or present late in the year. They can be long gone with the sooty mold still very much present

So no need to get your guy out to look now......he won't find anything either. And the leaves will be dropping soon anyway. Wait until the crapes start to push new growth in spring and keep a close watch then for sucking insects - they favor succulent new growth. And relatively easy to treat with insecticidal soap or just a strong stream of water from the hose.

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