Thrips
TreatablePest · spreads to other plants
Thrips rasp the surface of leaves and petals and drink what leaks out, leaving a silvery scarred appearance quite unlike anything else. The tiny black specks alongside the silvering are the reliable confirmation. They also transmit tomato spotted wilt virus, which is a much bigger problem than the feeding damage.
What it looks like
Silvery or bronze streaking on leaves and petals, speckled with minute black dots of excrement. Flowers open distorted or streaked. The insects themselves are slender slivers under a millimetre long that dart when disturbed.
How to confirm it
- Silvery or bronze streaks, not spots or holes.
- Tiny black varnish-like specks of excrement in the damaged areas.
- Flower buds opening deformed or with brown streaks on the petals.
- Tap a flower over white paper: the slivers that fall will run.
What to do
- 1Remove affected flowers and buds — that is where the population concentrates.
- 2Blue sticky traps for monitoring; thrips are drawn to blue more than yellow.
- 3Insecticidal soap or spinosad, repeated, since eggs are laid inside plant tissue and escape sprays.
What it gets confused with
One observation settles each of these.
Mites make fine even stippling and webbing; thrips make silvery streaks and black specks.
Preventing it next time
- Keep weeds down around beds; many are thrips reservoirs.
- Inspect new plants carefully, especially flowering ones.
Plants affected
Check these two things first
- Push a finger into the soil, two knuckles deep. Wet soil plus a wilting plant means too much water, not too little — and it is the commonest reason a plant is dying. Dry soil plus crisp leaves means the opposite. The leaves look nearly identical either way, so the soil is what tells you.
- Turn a damaged leaf over. Half of all diagnoses live on the underside: fuzz means downy mildew, fine webbing means spider mites, clusters of insects mean aphids. Nothing on the top of a leaf is as informative.
Most garden problems are cosmetic and resolve without treatment. Reach for a spray last, not first.