What's eating my petunia?

Petunias are commonly attacked by caterpillars (especially budworms/tobacco budworm), aphids on new growth, thrips that damage flowers, and slugs on young transplants. Tobacco budworm is the most damaging pest in the US, feeding inside buds and rendering flowers ragged or absent; it is often mistaken for a lack of flowering.

Caterpillars bore directly into buds before they open, eating the petals from inside; the only signs are small holes in petals, frass, and buds that fail to open or open tattered. Inspect buds in the evening; apply Bacillus thuringiensis (Bt) or spinosad spray at dusk when caterpillars are active; remove and destroy affected buds; repeat every 7–10 days.

Clusters on tender shoot tips and buds cause curled, distorted new growth and sticky honeydew deposits that attract ants and promote sooty mould. Knock off with a strong water spray; apply insecticidal soap; encourage natural predators; avoid excess nitrogen fertilising which produces lush, aphid-attractive growth.

Tiny insects rasp flower petals, leaving silvery streaks, brown edges, and distorted, short-lived blooms; also transmit tomato spotted wilt virus. Remove spent flowers promptly; apply spinosad or pyrethrin spray; use blue sticky traps to monitor; introduce Amblyseius cucumeris predatory mites for container plants.

Newly transplanted petunias and young seedlings are eaten at soil level overnight, leaving irregular holes in leaves or entire plants reduced to stubs. Apply iron phosphate pellets around transplants; hand-pick at night; use copper tape on containers; lay grit mulch around plants to deter slugs.