Whitefly
Whiteflies are tiny white sap-sucking insects (like minute moths) that congregate on the undersides of leaves and flutter up in a little white cloud when…
Whitefly at a glance
| Also known as | Glasshouse whitefly |
|---|---|
| Affected parts | Leaf undersides |
| Most at risk | Tropical/indoor and greenhouse trees; elms, fuchsia-relatives, many softwoods |
| Main cause | Sap-sucking whiteflies breeding on leaf undersides |
| Severity | Mild–moderate; weakens growth, honeydew/sooty mold |
| Reversible? | Yes, but persistent indoors |
What to look for
- Leaves: Clusters of tiny white flies and their flat, scale-like, semi-transparent nymphs on leaf undersides; yellowing, weak leaves; sticky honeydew and black sooty mold below.
- Whole tree: A cloud of tiny white flies rising when the tree is disturbed — the unmistakable sign.
Overview
Whiteflies are tiny white sap-sucking insects (like minute moths) that congregate on the undersides of leaves and flutter up in a little white cloud when the plant is shaken. They breed quickly in warm, sheltered conditions — indoors and in greenhouses especially — and, like aphids and scale, leave honeydew that fuels sooty mold.
Causes
Warm, still, sheltered conditions (indoors/greenhouse); introduction on new plants; and rapid breeding through the warm months.
Commonly confused with
Aphids and scale also cause honeydew but don't fly. Mealybugs are cottony and stationary. The flying-white-cloud behaviour is diagnostic of whitefly.
Which species are affected
Mainly tropical/indoor and greenhouse bonsai; also many soft-leaved outdoor species (elms, etc.) in warm weather.
Treatment
Spray insecticidal soap, neem, or horticultural oil to leaf undersides, repeating every few days (adults breed continuously); yellow sticky traps catch adults and monitor numbers; a gentle vacuum of disturbed adults helps indoors. Encanarsia parasitic wasps control them in greenhouses. Persist — they rebound quickly.
Prevention
Quarantine new plants; inspect undersides; use sticky traps as an early-warning system; keep good airflow; avoid over-feeding soft growth.