Hi, My crape myrtle (about 15-20 feet tall) has some kind of powdery mildew. The new growth coming up from the ground (which I just cut back), has white, powdery substance on it, and the whole tree looks kind of lethargic. What should I do?
Calvert County Maryland
We have been getting quite a few emails regarding powdery mildew, a fungal disease on crape myrtles. http://extension.umd.edu/hgic/powdery-mildew-trees-and-shrubs
It is not lethal to crape myrtles but is certainly not attractive. Control begins by selecting powdery mildew resistant varieties and you should consider this for the future.
Make sure the plant is in full sun and good air circulation to reduce humidity levels and allow proper plant spacing. Pruning for better air circulation also may help.
If severe, you can spray as soon as you notice the mildew. Check the label registration on fungicides for control information and timing. Fungicide treatments can help to protect new or un-infected foliage they are not curatives. It is up to you if you want to spray. You can monitor the situation this year.
Look at the list from the National Arboretum for more information on resistant varieties http://www.usna.usda.gov/Gardens/faqs/crapemyrtlefaq2.html#How%20hardy%20are
and Clemson http://www.clemson.edu/extension/hgic/pests/plant_pests/trees/hgic2002.html
So, is there a good chance that if I just patiently wait, that it may resolve next year without any poisons applied?
Thank you for your help!
Conditions can be different every season. However, If growing conditions are ideal, then most likely you will see it again and you have a susceptible cultivar.
The best defense is a resistant cultivar.