Peony wilt, sometimes called peony or botrytis blight, is a common fungal disease of peonies – both herbaceous peonies and tree peonies – that produces brown patches on the leaves and stems. Badly affected leaves and stems may then collapse and die.
Affected flower buds turn brown when small/pea sized, fail to develop, don’t open and die – resulting in no flowers. Infection may occur just below the flower bud, which then flops down. This is often referred to as peony bud blast disease.
Peony wilt is more prominent during cool, humid or wet weather from spring to early summer. In wet conditions, a fuzzy grey mould appears on affected parts.