Whitefly are small, sap-feeding insects that can affect houseplants, greenhouse crops and ornamental plants. They often remain hidden underneath leaves until the plant is moved or disturbed, when the adults rise into the air in a cloud of tiny white insects.
Identifying whitefly early can help prevent populations from increasing and spreading to nearby plants. Yellow sticky traps are useful for catching the flying adults, but affected leaves must also be inspected because eggs and immature whitefly remain attached to the plant.
WHAT DO WHITEFLY LOOK LIKE?
Adult whitefly are very small, pale insects with white, powdery wings. Although they resemble tiny moths, they are sap-feeding plant pests related to aphids and scale insects.
Adult whitefly are usually found on the undersides of leaves. When an affected plant is touched, watered or moved, they may fly upwards before settling again.
Whitefly eggs and immature stages are much less noticeable. They appear as small pale or scale-like marks attached to the underside of the leaf.
COMMON SIGNS OF WHITEFLY
Look for the following signs:
- Tiny white insects flying from plants when disturbed
- Adults resting underneath leaves
- Pale eggs or flat immature insects on leaf undersides
- Yellowing, weakened or distorted foliage
- Sticky honeydew collecting on leaves
- Dark sooty mould growing on the honeydew
- Reduced plant vigour during a heavy infestation
WHICH PLANTS CAN WHITEFLY AFFECT?
Whitefly can affect a wide range of ornamental and edible plants. They are particularly problematic in warm, protected environments such as greenhouses, conservatories and indoor growing areas.
Frequently affected plants can include tomatoes, cucumbers, peppers, aubergines, fuchsias, pelargoniums, poinsettias and numerous houseplants.
HOW TO CHECK A PLANT FOR WHITEFLY
Gently turn over several leaves and inspect their undersides. Check young growth as well as older foliage, paying attention to leaves showing yellowing or sticky deposits.
You can also gently disturb the plant. A group of tiny white insects flying upwards is a strong indication of adult whitefly activity.
Check nearby plants even if they do not yet show visible damage, as adult whitefly can move between them.
ISOLATE AFFECTED HOUSEPLANTS
If practical, move an affected houseplant away from the rest of the collection. This can reduce the opportunity for flying adults to reach uninfested plants.
Inspect any plant that was positioned nearby and avoid placing a newly purchased plant into the main collection until it has been checked carefully.
HOW YELLOW STICKY TRAPS HELP CONTROL WHITEFLY
Adult whitefly are strongly attracted to bright yellow surfaces. Yellow sticky traps use this response to draw the adults towards a high-tack adhesive that captures and holds them.
Capturing adults can reduce the number moving between plants and laying further eggs. The printed monitoring grid also helps you compare whitefly numbers over time.
The traps do not remove eggs or immature whitefly attached to leaves, so they must be combined with plant inspection and an appropriate treatment where necessary.
WHERE TO POSITION YELLOW STICKY TRAPS FOR WHITEFLY
Position traps just above or level with the upper plant canopy. Keep them close enough to intercept flying whitefly without allowing the adhesive to touch leaves or flowers.
In a greenhouse or polytunnel, distribute boards throughout affected areas and adjust their height as the crop grows. Concentrate additional traps around plants showing the greatest activity.
REMOVE HEAVILY AFFECTED LEAVES
Individual leaves carrying large numbers of eggs and immature whitefly may be removed where doing so will not damage the plant.
Place removed material directly into a bag and dispose of it responsibly. Do not leave affected leaves beside the plant or add them to an open compost heap near the growing area.
USE AN APPROPRIATE PLANT TREATMENT
A suitable biological-control organism or plant-protection treatment may be required when immature whitefly remain on the leaves.
Choose a product that specifically lists the target pest, plant type and intended growing environment. Follow its instructions carefully, including any guidance covering edible crops, repeat applications and biological controls.
Do not assume that a treatment suitable for an ornamental houseplant can also be applied to edible crops.
KEEP THE GROWING AREA CLEAN
Remove weeds and unwanted plant material that could provide alternative hosts. Clean growing benches, pots and equipment between crops, and inspect new plants before introducing them.
Whitefly reproduce quickly in warm conditions, so continue checking plants even after adult captures begin declining.
WHEN SHOULD YOU REPLACE THE TRAPS?
Replace each sticky board when it is full of insects, covered with dirt or no longer sufficiently sticky. Continue using traps after applying another control method so you can see whether adult activity is decreasing.
CREATE A COMPLETE WHITEFLY CONTROL PLAN
For more effective whitefly control:
- Inspect the undersides of leaves regularly
- Isolate affected houseplants where practical
- Use yellow sticky boards to catch flying adults
- Remove heavily infested foliage where appropriate
- Use a suitable treatment for immature stages
- Keep the growing area clean and free from weeds
Catch adult whitefly with the PlantPro Yellow Sticky Insect Traps – Pack of 50.
