I can't get rid of the aphids on my crepe myrtles. I have sprayed them with Neem organic oil and it did not work.
How to Get Rid of Aphids on My Crepe Myrtle
Certified GKH Gardening Expert
Pests like aphids will tend to attack plants that are stressed. If you are having a re-occuring problem with aphids, this would indicate that there is something else stressing the tree. Reducing that stress will help reduce the aphid problem.
I would also recommend that you continue to use neem oil. This will help to make sure you reach the whole population of aphids on the tree. Keep in mind that more than one application will be necessary.