Whitefly — identification and control

How to identify whitefly

Look for these symptoms on susceptible plants:

• White cloud of tiny moth-like adults rising when leaves are disturbed
• Sticky honeydew and sooty mould on lower leaves
• Yellow stippling and general leaf chlorosis
• Translucent oval scales on the underside of leaves (nymphs)
• Virus symptoms (e.g. TYLCV on tomatoes) in Bemisia-prone regions

Eggs to adults in about 3-4 weeks at 21-26 degC. Adults lay eggs on the youngest leaves; nymphs (scale-like) fix to one spot and feed for the rest of their development. Targeting nymphs is more effective than chasing adults.

Crops affected by whitefly

Whitefly are documented on the following host crops in authoritative extension sources. Click any crop for the full per-crop protocol, including symptoms specific to that host and the recommended biological control.

• Whitefly on tomatoeshigh

  White cloud of adult whitefly rising when you shake the plant; tiny scale-like nymphs on the underside of mid-canopy leaves; sticky honeydew and sooty mould on lower foliage.

  Severity: High — act quickly · From transplant under glass; outdoors from mid-summer. Greenhouse tomato is one of the most whitefly-susceptible crops in horticulture.

• Whitefly on peppersmoderate

  Silverleaf whitefly (Bemisia tabaci) and greenhouse whitefly on pepper undersides; honeydew, sooty mould, and irregular fruit ripening from heavy nymph feeding.

  Severity: Moderate — monitor closely · Greenhouse peppers: from transplant. Outdoor peppers: mid-to-late summer once flying adults arrive.

• Whitefly on cucumbershigh

  Greenhouse whitefly on the underside of cucumber leaves — flying clouds when the canopy is disturbed, sticky honeydew on lower leaves, leaf yellowing.

  Severity: High — act quickly · Under glass from the first true leaves; outdoors from mid-summer onwards.

• Whitefly on strawberriesmoderate

  Greenhouse whitefly (Trialeurodes vaporariorum) on the underside of strawberry leaves; honeydew, sooty mould, and irregular fruit ripening in heavy infestations.

  Severity: Moderate — monitor closely · Polytunnel and protected strawberry: from spring growth onwards. Outdoor strawberry: less common but mid-to-late summer.

Non-chemical controls

Start with the lowest-impact options before any spray. These work for the vast majority of home garden cases.

• Yellow sticky traps at canopy height — catch adults before they lay
• Silver reflective mulch around the base of plants — confuses incoming whiteflies
• Vacuum adults from foliage in early morning when cold and slow
• Remove and bin the lowest leaves where most nymphs settle
• Inspect transplants before bringing them home — most outbreaks start with one infested seedling

Biological controls

For greenhouse, polytunnel, and indoor production, biological controls give long-term suppression without the residue or pollinator harm of synthetic sprays.

• Encarsia formosa — parasitoid wasp, the standard agent for greenhouse whitefly on tomatoes and cucumbers (1 wasp per 4 plants, biweekly)
• Eretmocerus eremicus — better for silverleaf whitefly (Bemisia) in warmer conditions
• Delphastus catalinae — small black ladybird that eats whitefly eggs
• Macrolophus pygmaeus — predatory bug used in long-cycle greenhouse tomato

Organic and chemical spray options

Insecticidal soap and horticultural oil target nymphs on leaf undersides — repeat every 5-7 days because nymphs molt under a waxy shield. Spinosad and pyrethrin are stronger options; both are toxic to bees, so spray at dusk after pollinators have left. Avoid neonicotinoid drenches on flowering crops.

How to build a whitefly control protocol

1. Identify first. Snap a photo and confirm the species before treating — different pests respond to different protocols, and one wrong call wastes weeks. Open Growli for instant species ID.
2. Start with non-chemical control. Water blast, sticky traps, manual removal, reflective mulch, or quarantine — these alone clear roughly 60-70 percent of home cases.
3. Add biological control if you have a long-cycle crop. Greenhouse tomatoes, cucumbers, peppers, and indoor citrus all justify a single release of the right predator or parasitoid.
4. Layer in insecticidal soap or horticultural oil. Apply to thorough wetness on both leaf surfaces; repeat every 5-7 days for three weeks to catch successive hatches.
5. Reserve stronger sprays for outbreaks. Spinosad, pyrethrin, and species-specific options like Bti should be your second-line response, not your first.
6. Monitor weekly. Whitefly populations rebound from any single intervention. Two or three weeks of follow-up checks separate a fixed problem from a recurrence.

Common mistakes

• One-and-done spraying. Whitefly go through staggered hatches; a single spray misses everything that hatches afterwards. Always plan a 3-week protocol.
• Treating without confirming species. Insecticidal soap clears aphids but is wasted on slugs; Bti clears fungus gnat larvae but does nothing for spider mites. Wrong protocol equals wasted weeks.
• Spraying in hot sun. Soap and oil sprays burn leaves above 30 degC and on drought-stressed plants. Apply at dawn or dusk.
• Mixing biological control with broad-spectrum sprays. Pyrethroids and neonicotinoids wipe out predator releases. Use one strategy at a time, or stagger them by at least a week.

Frequently asked questions

How do I get rid of whitefly?

Whiteflies are 1-2 mm white moth-like insects that fly up in a cloud when foliage is disturbed. They suck sap, excrete honeydew, and vector several plant viruses. Yellow sticky traps catch adults, silver reflective mulch confuses incoming flights, and insecticidal soap or neem every 5 days knocks back nymphs. Encarsia formosa is the standard greenhouse parasitoid.

What does whitefly damage look like?

Look for: White cloud of tiny moth-like adults rising when leaves are disturbed; Sticky honeydew and sooty mould on lower leaves; Yellow stippling and general leaf chlorosis; Translucent oval scales on the underside of leaves (nymphs). Each host crop shows slightly different symptoms — see the per-crop pages linked above for details.

What is the best biological control for whitefly?

Encarsia formosa — parasitoid wasp, the standard agent for greenhouse whitefly on tomatoes and cucumbers (1 wasp per 4 plants, biweekly). Several other biocontrols are documented for specific conditions and host crops; see the full list above.

When during the season do whitefly appear?

Mid-to-late summer outdoors; year-round in greenhouses and conservatories. Eggs to adults in about 3-4 weeks at 21-26 degC. Adults lay eggs on the youngest leaves; nymphs (scale-like) fix to one spot and feed for the rest of their development. Targeting nymphs is more effective than chasing adults.

Are whitefly harmful to pets and people?

Whitefly themselves are not directly toxic to pets or people. The risk is from chemical sprays used to control them — use insecticidal soap, horticultural oil, or biological control wherever possible. Always check the product label for re-entry and harvest interval guidance, and confirm the active ingredient is currently approved via the UK HSE register or US EPA.

What plants do whitefly not affect?

Whitefly most commonly affect tomatoes, peppers, cucumbers, strawberries. Plants with thick, waxy, or hairy foliage typically resist this pest better than soft-leafed crops. For pet-safe houseplant alternatives that resist most common pests, see our pet-safe houseplants guide.

Can I use the same protocol indoors and outdoors?

The biological-control choices change (indoor releases of ladybirds rarely work; predatory mites and parasitoid wasps do), but the spray protocols (insecticidal soap, horticultural oil, neem) translate directly. Outdoor cases benefit from reflective mulches and companion planting; indoor cases benefit from quarantine and routine wipe-downs.

Sources

Identification and control guidance sourced from US Cooperative Extension publications (UC IPM, NC State, UMD, UMN, Penn State, CSU, UF/IFAS EDIS), Clemson HGIC fact sheets, Royal Horticultural Society guidance, and Cornell NYS IPM Biocontrol fact sheets. Reviewed by the Growli editorial team in May 2026.

Keep going

• All 8 garden pests covered in this guide
• Garden pest identification — complete article
• Companion planting chart (pest-deterrent pairings)
• Common houseplant diseases