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Whitefly
Trialeurodes vaporariorum
PestLow impact
Tiny white-winged insects that cluster on leaf undersides and fly up in clouds when disturbed. Both adults and immature stages suck plant sap, weakening growth and depositing honeydew that encourages sooty mould.
Currently in peak season - extra vigilance worthwhile.
Key facts
- Type
- Pest
- Active season
- Jun - Oct
- Peak season
- Jul - Sep
- Vulnerable stages
- Growing · Harvesting
- Spread rate
- fast
- If confirmed
- Act soon
Signs & symptoms
- -clouds of tiny white insects rising when plants are disturbed
- -pale, scale-like nymphs in neat rows on leaf undersides
- -sticky honeydew and sooty black mould on leaves below the colony
- -leaf yellowing and weakened growth in heavy infestations
Management
Do now
- -Hang yellow sticky traps near affected plants to monitor and reduce adult numbers
- -Remove heavily infested leaves and bin - do not compost
- -Encourage natural predators such as parasitic wasps
- -Introduce biological control (Encarsia formosa) in glasshouse situations
Prevention
- -Avoid overcrowding plants
- -Reflective mulch can deter adults from landing on plants
- -Ventilate polytunnels and glasshouses well to reduce pest and disease pressure
Further reading
- -The visible flying adults are only part of the problem - the flat, scale-like nymphs on leaf undersides do sustained feeding damage and are harder to control
- -Whitefly reproduce rapidly in warm conditions and adults can develop resistance to chemical controls quickly