Whiteflies are sap-feeding insects of the family Aleyrodidae, about 1-2 mm long, with powdery white wings held over the body. The two that matter on cannabis are the greenhouse whitefly (Trialeurodes vaporariorum) and the silverleaf or sweetpotato whitefly (Bemisia tabaci). Adults fly up in a cloud when a plant is shaken. Nymphs are flat, oval and fixed to leaf undersides like tiny scales.
In practice
Feeding yellows leaves and deposits honeydew, which grows black sooty mould. Bemisia is also a virus vector; whitefly-transmitted lettuce chlorosis virus has been reported on cannabis. Yellow sticky traps catch adults and show population trends. Biological control uses Amblyseius swirskii against eggs and young nymphs, parasitic wasps (Encarsia and Eretmocerus species) and entomopathogenic fungi. Bemisia populations resist many insecticide groups, so prevention and biocontrol carry more weight than sprays. Check what is registered for cannabis locally.
Don't confuse with
- Aphids: no wings in most colony members; they walk rather than fly up.
- Fungus gnats: dark grey flies that hover near the medium.
- Mealybugs: waxy and crawling, never flying.
An infectious particle of nucleic acid in a protein coat that replicates inside plant cells; on cannabis, often insect-spread and incurable once infected.A coloured card coated in non-drying glue that catches flying insects, used mainly to monitor pest trends: yellow for gnats, whiteflies and aphids, blue for thrips.Using living natural enemies, such as predators, parasitoids, nematodes and microbes, to suppress pests and diseases instead of, or before, chemical sprays.A warmth-loving generalist predatory mite that eats thrips larvae, whitefly eggs and nymphs and broad mites, and can persist on pollen.Tiny parasitic wasps of the genus Aphidius that lay eggs inside aphids; the larva kills the host from inside, leaving a swollen tan mummy.Pest and disease prevention by changing how the crop is grown, such as humidity, airflow, spacing, watering and cultivar choice, so pests and pathogens struggle to establish.Small soft-bodied sap-sucking insects of the family Aphididae that cluster on stems and leaf undersides, excrete sticky honeydew and multiply rapidly by live birth.Small dark flies of the genus Bradysia (family Sciaridae) whose larvae live in wet growing media, feeding on fungi, organic matter and young roots.An insect-killing fungus whose spores germinate on contact, penetrate the cuticle and kill soft-bodied pests such as whiteflies, thrips, aphids and root aphids.
