Thrips: how to recognise and treat it

Pest

Symptoms

Leaves turn dull green, then silvery-white on the upper surface, marked with many tiny black specks of excrement.
Fine pale stippling or flecking; white flecks on flower petals, and heavily attacked buds may not open.
Distorted, stunted shoot tips and leaves; fruit can be scarred or misshapen.
Narrow insects up to 2 mm — yellowish to blackish-brown adults with fringed wings, paler wingless young.
Some thrips spread viruses such as tomato spotted wilt virus, especially to young vegetable and flower plants.

In a greenhouse, hang blue sticky traps among the plants to catch thrips and watch their numbers; outdoors they catch too many other insects.
Cut off and destroy badly infested shoot tips on a few small plants.
In a greenhouse, release predatory mites or the predatory bug Orius laevigatus.
Spray insecticidal soap, horticultural or neem oil, azadirachtin or pyrethrins, covering buds and shoot tips thoroughly; repeat as the label directs while thrips remain.

Spinosad is usually more effective than contact sprays and reaches thrips in protected plant parts; follow the label dose and pre-harvest interval.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Control weeds next to the garden — thrips move from drying weedy areas onto garden plants.
When buying houseplants, check the flowers and avoid plants with thrips or pale flecks on the petals.
Spare lacewings, minute pirate bugs, predatory mites and predatory thrips — avoid persistent insecticides.
Established shrubs usually tolerate the silvering; sprays will not restore damaged leaves, only new growth looks clean.

Figures checked against these sources.