Crape myrtles are susceptible to their own species of aphids, and black sooty mold soon follows an infestation. It can be quite a mess unless you get rid of the aphids, after which the BSM will flake away on its own. I suspect that this is your problem. The hybrid crape myrtles are bred to be resistant to aphids.

There is also a fairly new scale insect that is making crapes a challenge to grow. It starts out as a white mass of these small insects, also quickly covered by BSM. The scale insects are difficult to control.

So will neem oil get rid of the aphids?

Some pictures would help id the pest.

Is it possible to spray neem in July in Texas without damaging the foliage?

That I dont know........will have to check on that. I also heard that a spray of dish soap/water, leave on 15 minutes then spray with water will remove the mold. Does anyone know if neem can be sprayed in 90 degree + heat?

there is a relatively newly identified (2004, n. texas and now found in most of the southeasten u.s. up to delaware and the northwest pacific coast ) disease named "crapemrtle bark scale"https://www.uaex.uada.edu/yard-garden/resource-library/crapemyrtle/crapemyrtle_bark_scale.aspx. perhaps search that disease for treatment options.

i knew that eventually something would come around and take its toll of these ubiquitously planted small trees...they are everywhere in my area.

That is a very informative link but it should be noted that CMBS is not a disease but an insect issue. And it is treated in the same manner as other types of scale insect infestations, which should be noted, do not include the use of neem oil.

But if you have a scale problem of any kind, the insects themselves should be quite visible, clustering along branches and stems and the undersides of leaves. Scale insects are sucking insects, similar to aphids, and both will produce the sticky, honeydew excrement that sooty mold grows on.

Aphids are a bit harder to detect given their smaller size. Neem oil will work on them but so will just a strong stream of water, hosing down the tree and its foliage thoroughly and repeated as necessary. No need for any chemical disturbance to any pollinators present.

The sooty mold itself does really no harm to the tree except for making it look unsightly, although a very heavy presence of SM can interrupt or impede photosynthesis. It is not necessary to attempt to remove it all or wash it off.

And any pesticides - other than plain water - should never be applied during the sunny, hot periods of the day. Early morning or late evening.

It appears that your crepe myrtles are suffering from sooty mold, likely due to an aphid infestation. Aphids consume the sap of plants and excrete a sticky residue called honeydew, which fosters the growth of sooty mold. To manage this issue, start by thoroughly inspecting the plants for aphids, which are small, pear-shaped insects that gather mainly on the undersides of leaves and new growth. You can then dislodge the aphids and wash away the mold by spraying the plants with a strong water jet from your garden hose. For ongoing treatment, consider applying insecticidal soap or neem oil according to product directions, usually about once a week until the aphids no longer appear.

Additionally, promoting natural predators such as ladybugs and lacewings can help control aphid populations, as these beneficial insects feed on aphids. If certain areas of your plants are heavily infested, pruning them can remove the source of infestation and improve air circulation, further helping to prevent the recurrence of mold.

If these methods do not control the aphid population effectively, you may consider using imidacloprid as a last resort. Imidacloprid is a systemic insecticide that is highly effective against aphids. It should be applied as a soil drench to minimize impact on non-target insects and ensure it is absorbed through the roots, providing protection throughout the plant. Be sure to apply it according to the label's instructions and avoid use during the plant's blooming period to protect pollinators. Regular monitoring and prompt action will help keep your crepe myrtles healthy and free from aphids and mold.

Good luck!

Judith, I’m in D/FW and have this problem periodically. I just blast the trunk and leaves with a strong stream of water daily and it goes away within a couple of weeks. I never have to use any sort of special treatment.

I’ve been growing various varieties for 30+ yrs and at several different houses and have never lost one to this issue. It’s just a temporary annoyance.