Barberry powdery mildew

Symptoms

A fine white-to-greyish powdery coating develops on the upper and lower leaf surfaces, on young shoot tips and on the green stems of Berberis thunbergii. Affected new growth becomes stunted, puckered or twisted, and badly infected leaves turn yellow then brown and drop early, leaving thin, distorted shoots. The mealy bloom wipes off easily with a finger, distinguishing it from dust or spray residue, and late in the season tiny black pinhead fruiting bodies (chasmothecia) may speckle the white mats. On purple-leaved cultivars the silvery-white film is especially conspicuous against the dark foliage.

Plants affected

• Japanese barberry

Common questions

How do I recognise Barberry powdery mildew on Japanese barberry?

A fine white-to-greyish powdery coating develops on the upper and lower leaf surfaces, on young shoot tips and on the green stems of Berberis thunbergii. Affected new growth becomes stunted, puckered or twisted, and badly infected leaves turn yellow then brown and drop early, leaving thin, distorted shoots.

Do I have to report Barberry powdery mildew?

No. Barberry 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 Barberry 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.