Thrips
Tiny, slender insects that rasp leaf and flower surfaces, leaving silvery streaks, curled leaves and distorted flowers.
Also known as: Thunderflies, Chilli thrips
Symptoms and identification
Silvery or bronze streaks and speckles on leaves, often with tiny black dots of excrement. New leaves curl upwards and become brittle, especially on chilli. Flowers are streaked, spotted or fail to open. Tapping a flower over white paper reveals tiny moving yellow or black insects.
Causes
Thrips breed rapidly in hot, dry weather and hide in buds and folded leaves where sprays struggle to reach. They fly between plants and arrive on cut flowers and new plants.
Organic treatment
Spray neem oil or insecticidal soap every 5 days for three weeks, directing the spray into buds and leaf folds. Pick off and bin badly affected flowers. Blue sticky traps help catch adults.
Prevention
Check flowers and new leaves weekly in dry weather. Hang blue or yellow sticky traps, keep plants well watered, and remove weeds that host thrips. Quarantine new plants.
Chemical treatment (use with care)
For serious infestations, use an insecticide labelled for thrips (for example spinosad-based products, which are allowed in many organic systems), following the label and avoiding open flowers visited by bees.