# Whiteflies on cannabis: ID and IPM

> Whiteflies are tiny white moth-like sap feeders that rise in a cloud when you shake a plant; nymphs sit flat under leaves and drip honeydew. Identify the species, monitor with yellow cards, and use Encarsia formosa (greenhouse whitefly) or Eretmocerus (warmer rooms, silverleaf whitefly) plus predatory mites, keeping sprays out of flower.

- Canonical: https://genetixbay.com/knowledge/pests/whiteflies.html
- Category: Pests · Level: Beginner
- Evidence: Supported · Status: Draft: awaiting expert review (some figures are being checked)
- Stage: Veg, Transition, Flower · Systems: Any system
- Updated: 2026-10-31 · Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay Knowledge Base (genetixbay.com/knowledge)"

## Questions and answers

**What are the tiny white flies on my cannabis?** Tiny white moth-like insects that rise in a puff when you shake a cannabis plant are whiteflies. Adults are about 1.5 mm with white wings and rest on leaf undersides, while flat, oval, translucent nymphs sit motionless below. Indoors the two main species are greenhouse whitefly and silverleaf whitefly. Unlike aphids, whiteflies lack tail pipes and fly readily when disturbed.

**How do I get rid of whiteflies indoors?** Get rid of whiteflies indoors by monitoring with several yellow [sticky cards](https://genetixbay.com/knowledge/glossary/sticky-trap.md) near the canopy, identifying the species, and releasing the matching parasitoid early: Encarsia formosa for greenhouse whitefly, Eretmocerus for silverleaf whitefly and warmer rooms. Phase out residual insecticides before release. Quarantine incoming plants and keep houseplants out. Soaps and oils are for veg only.

**Encarsia or Eretmocerus for whiteflies?** Choose Encarsia formosa for greenhouse whitefly in rooms of about 21 to 27 °C (70 to 80 °F) with 50 to 80% RH; its adults stop flying below about 18 °C (65 °F). Choose Eretmocerus for silverleaf whitefly, which Encarsia does not parasitise, and for warmer rooms. Mixtures are commonly sold. Continue releases until about 80% of the population is parasitised.

**Why are my leaves sticky with black mould?** Sticky cannabis leaves with black mould are coated in honeydew, sugary waste from sap-feeding insects, on which black sooty mould grows. Whiteflies and aphids both cause it. Shake the plant: a cloud of tiny white flies means whiteflies, while clusters of soft pear-shaped insects with tail pipes mean aphids. Check the leaves directly above the mould for the source.

**Short answer.** Shake a plant and a puff of tiny white flies lifts off: whiteflies. They are less common on cannabis than mites or thrips, but they breed steadily indoors, drip honeydew, and can carry [broad mites](https://genetixbay.com/knowledge/glossary/broad-mite.md) between plants. Monitor with yellow cards, work out which species you have, and release the matching [parasitoid wasp](https://genetixbay.com/knowledge/glossary/aphidius.md) early. Keep sprays to veg.

## What's happening

Adults and nymphs suck [phloem sap](https://genetixbay.com/knowledge/glossary/phloem.md) and excrete honeydew that leads to sticky leaves and black sooty mould; ants may farm them [1]. Two species matter indoors: greenhouse whitefly (Trialeurodes vaporariorum) and silverleaf/sweetpotato whitefly (Bemisia tabaci) [2]. Broad mites can hitch rides on adult whiteflies [6].

**Lifecycle.** Eggs on leaf undersides → mobile first-instar "crawler" → three further flat, oval, immobile nymphal stages → winged adult [1]. Egg to adult takes roughly 3–4 weeks at greenhouse temperatures (temperature-dependent).

## How to recognise it

- Adults ~1.5 mm, white wings, resting on leaf undersides; fly up when disturbed.
- Nymphs: flat, translucent-to-pale scales on undersides; pupae are thicker with visible red eyes.
- Honeydew and sooty mould on leaves below.
- Greenhouse whitefly holds wings flat and overlapping, almost triangular; silverleaf holds them tent-like with a gap showing the yellow body (lens ID).
- Parasitised greenhouse-whitefly pupae turn black (Encarsia) or yellow-brown (Eretmocerus). Encarsia exit holes are round; healthy adults leave T-shaped slits [1].

## Numbers that matter

| Parameter | Value | Notes |
|---|---|---|
| Adult length | ~1.5 mm | |
| Encarsia formosa best range | 21–27 °C (70–80 °F), 50–80% RH | Adults stop flying below ~18 °C (65 °F) [2] |
| Eretmocerus eremicus | performs better than Encarsia at higher temperatures | [2] |
| Encarsia host | greenhouse whitefly only | Eretmocerus also attacks silverleaf [2] |
| Release goal | continue until ~80% of the population is parasitised | [2] |
| [Action threshold](https://genetixbay.com/knowledge/glossary/action-threshold.md) | none established for cannabis | Grower practice: first adults on cards |

## What to check first

1. Confirm with a lens; separate from aphids (no tail pipes, fly readily).
2. Yellow sticky cards near the canopy, sticky side facing plants, out of direct sun; replace or clean regularly. Whiteflies do not fly far, so you need several [1].
3. Identify species (lab or lens).
4. Find the source: houseplants, vegetable transplants, outdoor plants near intakes.

## How to fix it

Registrations differ by jurisdiction; check local regulations and the label. No products or rates here.

### Cultural
- Quarantine incoming plants; keep vegetable seedlings and houseplants out of the grow room.
- Remove weeds and other host plants near intakes.
- Phase out residual insecticides well before releasing parasitoids [2].

### Physical
- Yellow sticky cards (monitoring and minor trapping) [1].
- Vacuuming adults off plants early in the morning, when they are sluggish (Grower practice).
- Insect screening on intakes where feasible.

### Biological
- **Encarsia formosa:** parasitoid of greenhouse whitefly; best at 21–27 °C and 50–80% RH; very sensitive to pesticide residues on plants and surfaces [2].
- **Eretmocerus eremicus / E. mundus:** better in warmer rooms and against silverleaf whitefly; do not release in direct sunlight [2][3]. Mixtures of Encarsia and Eretmocerus are commonly sold [2].
- **[Amblyseius swirskii](https://genetixbay.com/knowledge/glossary/amblyseius-swirskii.md):** [predatory mite](https://genetixbay.com/knowledge/glossary/predatory-mite.md) that eats whitefly eggs and young nymphs and also thrips larvae.
- **Generalist predators:** lacewings, [minute pirate bugs](https://genetixbay.com/knowledge/glossary/orius.md) and some [lady beetles](https://genetixbay.com/knowledge/glossary/ladybird.md) prey on whiteflies [1].
- **Entomopathogenic fungi** (Isaria fumosorosea, Beauveria bassiana): listed in extension guidance [4]; need humidity.

### Least-toxic options
- **[Insecticidal soaps](https://genetixbay.com/knowledge/glossary/insecticidal-soap.md)** and **[horticultural oils](https://genetixbay.com/knowledge/glossary/horticultural-oil.md):** contact; target undersides; repeat at short intervals because eggs and pupae are tolerant.
- Avoid broad-spectrum residuals that kill parasitoids for weeks [2].

### What not to do in flower
- Do not spray buds.
- Do not use [systemic insecticides](https://genetixbay.com/knowledge/glossary/contact-vs-systemic.md); not registered on cannabis in most places, and residues persist.
- Do not raise RH in late flower to help fungal biopesticides.
- In flower, rely on parasitoids and predators established in veg.

## How to confirm it worked

- Card counts fall over 3–4 weeks.
- Most pupae on lower leaves are parasitised (dark or exit holes round).
- New leaves stay free of honeydew.

## Common mistakes

- Releasing Encarsia against silverleaf whitefly; it does not parasitise it [2].
- Releasing parasitoids into a room with fresh pesticide residues.
- Relying on cards for control instead of monitoring.

## Evidence

- Biology and honeydew damage: *Established* [1].
- Encarsia and Eretmocerus biology and temperature preferences: *Established* in greenhouse crops [2][4]; the UMass silverleaf guide is old (1996) [3].
- Use on cannabis: *Supported* by extrapolation; cannabis-specific trials are lacking.

## Sources

1. UC IPM. Pest Notes: Whiteflies (Publication 7401). https://ipm.ucanr.edu/PMG/PESTNOTES/pn7401.html
2. UMass Extension. Whiteflies on greenhouse crops. https://www.umass.edu/agriculture-food-environment/greenhouse-floriculture/fact-sheets/whiteflies-on-greenhouse-crops
3. UMass Extension. Biological control: grower's guide to using biological control for silverleaf whitefly on poinsettias. https://www.umass.edu/agriculture-food-environment/greenhouse-floriculture/fact-sheets/biological-control-growers-guide-to-using-biological-control-for-silverleaf-whitefly-on
4. UConn IPM. Biological Control of Whiteflies. https://ipm.cahnr.uconn.edu/ipm-biological-control-of-whiteflies
5. Michigan State University Extension. Controlling whitefly in the greenhouse. https://canr.msu.edu/news/controlling_whitefly_in_the_greenhouse
6. UConn IPM. Managing Broad Mites on Greenhouse Crops. https://ipm.cahnr.uconn.edu/ipm-managing-broad-mites-on-greenhouse-crops