Crape Myrtle - sick or bugs?

geeman1082August 24, 2013

Hi All,

We have a grouping of Natchez Crape Myrtles on the south side of our house. Late last summer they started looking like the photo below, dark leaves, fewer flowers, and dark staining on the gravel underneath.

I hired a new yard guy late last fall, a guy who worked many years for a local nursery before striking out on his own. He didn't have the benefit of seeing them with leaves, but based on his inspection of the branches and stains on the gravel, he diagnosed aphids or something like that, and said that he would spray for them this year. He has sprayed, but he was apparently wrong with his diagnosis.

I will post a couple of closeups as well.

Any ideas or suggestions would be much appreciated!

Regards,
Greg

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geeman1082

A close-up ... some of the leaf damage was caused by Japanese Beetles in June, which happens every year.

    Bookmark   August 24, 2013 at 1:37PM
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geeman1082

And lastly, a second close-up, which I took to show curled leaves and little white spots.

    Bookmark   August 24, 2013 at 1:38PM
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rhizo_1 (North AL) zone 7

Your description and the first image absolutely indicates aphids and the subsequent black sooty mold that goes along with an infestation. The black sooty mold will grow on anything that the aphid's sugary excrement coats....leaves, soil, stems, lawn furniture, etc.

I wonder if you are certain that these plants are Natchez. First of all, they don't look like Natchez to me. Secondly, Natchez has proved to be highly resistant to crape myrtle aphids.

I wonder if the splotched and blackened foliage we see in these images are a result of pesticide treatments. Do you know what was used?

My preferred aphid treatment on crapes is two or three winter season applications of dormant oil, including one just before bud break. Aphids overwinter as eggs, which can be effectively smothered by horticultural oil.

In the spring, the young leaves MUST be examined regularly for aphids....which are perfectly visible and easily recognizable. They can be sprayed off with sharp streams of water if caught early.

In their normal range, Natchez easily and swiftly attains a height and width of 20-30 feet.

    Bookmark   August 24, 2013 at 8:03PM
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rhizo_1 (North AL) zone 7

Your description and the first image absolutely indicates aphids and the subsequent black sooty mold that goes along with an infestation. The black sooty mold will grow on anything that the aphid's sugary excrement coats....leaves, soil, stems, lawn furniture, etc.

I wonder if you are certain that these plants are Natchez. First of all, they don't look like Natchez to me. Secondly, Natchez has proved to be highly resistant to crape myrtle aphids.

I wonder if the splotched and blackened foliage we see in these images are a result of pesticide treatments. Do you know what was used?

My preferred aphid treatment on crapes is two or three winter season applications of dormant oil, including one just before bud break. Aphids overwinter as eggs, which can be effectively smothered by horticultural oil.

In the spring, the young leaves MUST be examined regularly for aphids....which are perfectly visible and easily recognizable. They can be sprayed off with sharp streams of water if caught early.

In their normal range, Natchez easily and swiftly attains a height and width of 20-30 feet.

    Bookmark   August 24, 2013 at 8:04PM
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geeman1082

Thanks for the reply. I dug out the book where we've been keeping our landscaping records, and you are correct. These are Burgundy Cotton, not Natchez. My apologies.

Now that I realize my error, I do seem to recall that we originally wanted Natchez for the white flowers, but we were told that it would not be a good choice for our location. We chose this style as a substitute because the flowers are mostly white. Hopefully the aphids won't make us regret that choice!

I do not know what my guy used on the bushes, but it obviously didn't work ... I will check with him and give him your suggestion (or, more likely, do it myself this winter).

And yes, I know that I'll be trimming these back pretty regularly once they are well established. We planted them here (in MO) because we so enjoyed them when we lived in SC, although the choices were a bit more limited due to the climate differences. (We also have some azaleas for the same reason.)

Thanks again for the help!

    Bookmark   August 24, 2013 at 8:37PM
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rhizo_1 (North AL) zone 7

It appears to me that the aphids are gone. Are they? A quick look at the younger growth will give you that information. If so, any black sooty mold will eventually dissolve and go away. It's feeding on the honeydew, not the plant.

Now that I know that your plant is one of the burgundy-leafed hybrids, I don't really see a problem. Maybe some pesticide damage. I strongly recommend that my suggested dormant season treatment be instituted after leaf drop this year.

This post was edited by rhizo_1 on Sun, Aug 25, 13 at 7:01

    Bookmark   August 25, 2013 at 6:38AM
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