Honeysuckle powdery mildew

Symptoms

A fine, white-to-greyish powdery coating develops on the upper surfaces of leaves and on young shoots, looking as if the foliage has been dusted with flour. The mealy growth can be rubbed off with a finger, leaving the leaf surface beneath intact at first; heavily colonised leaves later turn yellow, curl, dry out brown and drop early. On strongly affected plants the coating also spreads to flower buds and stems, stunting new growth and dulling the flowering display. Late in the season tiny black dot-like fruiting bodies (chasmothecia) may speckle the white mat.

Easily confused with

• grey mould (Botrytis)

  How to tell them apart: Both fungi grow as a 'mould' on honeysuckle leaves and flowers, but Erysiphe lonicerae (powdery mildew) is a dry, white-to-grey superficial powder, mainly on the UPPER side of otherwise firm green leaves, that wipes off with a finger and leaves the tissue beneath alive. Botrytis cinerea (grey mould) is a fuzzy grey-brown sporulating felt that grows ON dead, water-soaked, rotting tissue — collapsing flowers, buds and soft shoots — and is associated with brown rot and slime, not a dusting on healthy leaves. Powdery mildew loves warm dry days with humid nights; grey mould loves cool, wet, stagnant conditions and dead plant material.