Thrips: signs, damage and safe control

Thrips are tiny, slender insects, only a millimetre or two long, with narrow fringed wings. They rasp at plant surfaces and feed on the sap, and they favour flowers and new growth.

How to spot them:

1. Silvery or pale, streaky patches on leaves and petals.
2. Distorted or discoloured flowers and new leaves.
3. Tiny black specks of frass on the damaged areas.
4. Thrips themselves, which are hard to see. Tap a flower over a sheet of white paper and look for slivers that move.

The damage they do: thrips scar leaves and flowers and can spread plant viruses. Light damage is cosmetic, but heavier infestations knock plants about.

How to manage them, safely:

1. Hose them off and remove badly affected growth. This alone brings numbers down.
2. Use blue or yellow sticky traps to catch the adults and keep an eye on numbers.
3. Encourage predators. Ladybirds, lacewings and predatory mites all eat thrips (companion planting helps bring them in).
4. Try insecticidal soap or neem oil if needed. Spray in the cool of the day and avoid open flowers to protect bees.

We do not recommend harsh synthetic sprays for thrips on food plants. They harm the very predators that keep thrips in check, and the gentle options work. For the full picture, see our guide to managing pests safely.

Plan your patch: our free planting calendar shows what to plant now where you live. Ready to grow? Browse our raised garden beds or build your own with the garden bed builder.

Image: Pearson Scott Foresman, public domain, via Wikimedia Commons.