Dr. Phyto

Japanese barberry

Berberis thunbergii

Diseases & pests on this plant

• Barberry powdery mildewErysiphe berberidis

  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.

• vine weevilOtiorhynchus sulcatus

  Distinctive U-shaped notches around leaf margins (similar to Sitona on legumes), C-shaped white legless larvae (up to 10mm) feeding on roots inside pots, sudden plant collapse during summer despite normal watering (larvae have eaten all roots), adults visible at night feeding on foliage.

• olive Verticillium wiltVerticillium dahliae

  Half a tree wilting in summer while the other half stays green, blackish discoloration in cross-section of affected wood, partial recovery in winter then relapse, dieback over 2–4 seasons.

• Phytophthora root + crown rotPhytophthora cinnamomi

  Sudden wilting + collapse of mature trees during summer heat stress, dark sunken cankers at base of trunk often oozing dark sap, root system rotted away to small white feeder roots only, gradual general decline + sparse foliage 1-3 years before final collapse, characteristic V-shaped soil-line lesion when bark peeled back.