What's eating my geranium (pelargonium)?

Pelargoniums are troubled by vine weevil (whose grubs eat roots), geranium bronze butterfly caterpillars (in UK/Europe), spider mites in hot dry conditions, and botrytis grey mould in cool, damp weather. Vine weevil is the most destructive pest, causing sudden wilting and plant death as grubs devour the root system over winter.

Notched, scalloped leaf margins from adult beetles feeding at night; far more severely, C-shaped white grubs eat roots and the stem base over autumn/winter, causing plants to wilt suddenly and collapse. Apply Steinernema kraussei or Heterorhabditis bacteriophora nematodes to compost in autumn (soil temp 5–20°C); repot annually to inspect roots; remove and destroy any grubs found; use vine weevil-specific compost treatments for container plants.

Small caterpillars bore into stems and flower buds, causing wilting shoots and flowers; dark frass and entry holes are visible at the base of buds and in stems. Check plants regularly for wilting shoots; remove and destroy affected stems; there is no approved insecticide for this pest in the UK — vigilance and removal is the only control.

Yellow stippling on leaf upper surfaces and fine webbing on undersides; leaves dry and drop in severe cases, particularly on overwintered indoor plants in low humidity. Raise humidity; spray with water to dislodge mites; apply neem oil or insecticidal soap to undersides of leaves; introduce predatory mites for persistent infestations.

Fluffy grey mould on leaves, stems, and flowers during cool, damp, or overcrowded conditions; brown, water-soaked spots that spread rapidly and cause collapse of affected parts. Remove infected tissue immediately; improve air circulation by spacing plants; avoid wetting foliage; do not over-water; apply copper-based fungicide preventatively in high-risk conditions.