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.
Fix it
What the treatment above uses, from our shop:
Prevention
Quarantine new plants; inspect undersides; use sticky traps as an early-warning system; keep good airflow; avoid over-feeding soft growth.