Whiteflies
Small white flying insects that gather under leaves, sucking sap, spreading viruses and leaving sticky honeydew.
Also known as: Whitefly, Silverleaf whitefly
Symptoms and identification
Clouds of tiny white insects fly up when the plant is disturbed. The undersides of leaves carry flat, pale, scale-like nymphs. Leaves turn yellow, become sticky with honeydew and later grow black sooty mould. On tomato and chilli, whiteflies spread leaf curl viruses that cause stunted, crumpled leaves.
Causes
Whiteflies breed rapidly in warm weather and sheltered places such as greenhouses and balconies. They arrive on new plants and from nearby infested crops, and are attracted to soft, lush growth.
Organic treatment
Hang yellow sticky traps at plant height. Spray neem oil or insecticidal soap on the undersides of leaves every 5–7 days for several weeks. Vacuuming adults off plants in the early morning, when they are sluggish, helps reduce numbers quickly.
Prevention
Check the undersides of leaves when buying plants. Hang yellow sticky traps near susceptible plants to catch adults early. Avoid overfeeding with nitrogen, and grow marigolds and herbs nearby to attract natural predators.
Chemical treatment (use with care)
For severe infestations on ornamental plants, use an insecticide labelled for whiteflies following the label. On vegetables, use only products approved for edible crops and observe the waiting period before harvest.