Crape myrtle powdery mildew

Symptoms

A superficial white-to-grey, felt-like powdery coating develops on young shoots, buds and the upper surface of new leaves, often starting as small circular patches that merge to cover the whole leaf. Infected young leaves curl, cup, pucker and become distorted, frequently flushing reddish or purple, and severely affected shoot tips are stunted. Flower buds and panicles can be coated and blasted, so they fail to open or produce few, deformed blooms. Badly diseased leaves yellow and drop early; in humid weather the white growth is most intense on the newest growth.

Plants affected

• crepe myrtle

Easily confused with

• Crape myrtle Cercospora leaf spot

  How to tell them apart: Erysiphe lagerstroemiae (powdery mildew) forms a superficial, white-to-grey, dry powdery felt that wipes off, mainly on new shoots, flower buds and the UPPER side of young leaves, which curl and distort. Pseudocercospora lythracearum (Cercospora leaf spot) instead produces discrete dark-brown to maroon angular/round spots, often with a yellow halo and grey centre, mostly on older, lower leaves which turn yellow-orange-red and drop heavily — there is no white removable coating and the leaves are not distorted.

Common questions

How do I recognise Crape myrtle powdery mildew on crepe myrtle?

A superficial white-to-grey, felt-like powdery coating develops on young shoots, buds and the upper surface of new leaves, often starting as small circular patches that merge to cover the whole leaf. Infected young leaves curl, cup, pucker and become distorted, frequently flushing reddish or purple, and severely affected shoot tips are stunted.

Do I have to report Crape myrtle powdery mildew?

No. Crape myrtle powdery mildew is not a notifiable organism, so there is nothing to report to an authority. Treat it as a normal garden problem.

How is Crape myrtle powdery mildew treated?

Mainly with biological and cultural measures — removing affected material, changing the conditions that favour it, and treating with agents approved in your country. The exact steps and their timing depend on the plant, the season and where you live: Dr. Phyto works them out in a free diagnosis.