Whitefly Virus Transmission
Overview
Some whitefly species transmit economically important plant viruses.
Tobacco or silverleaf whitefly (Bemisia tabaci) is especially important because it can transmit many begomoviruses and other plant viruses between susceptible hosts.
Glasshouse whitefly (Trialeurodes vaporariorum) is primarily important for feeding damage, honeydew and sooty mould and is generally much less important as a virus vector.
Species identification therefore affects both biological-control choice and plant-health risk assessment.
UK plant-health significance
Bemisia tabaci is a regulated plant pest in Great Britain.
Suspected findings should be treated seriously and reported through the appropriate plant-health route.
Tomato yellow leaf curl virus and related viruses are also important regulated plant-health threats associated with Bemisia tabaci.
Tomato yellow leaf curl virus
Tomato yellow leaf curl virus is a begomovirus transmitted by Bemisia tabaci.
Susceptible tomato plants may develop:
- upward leaf curling
- yellowing
- shortened internodes
- stunting
- reduced flowering
- reduced fruit set
- poor crop development
Young plants infected early may be particularly badly affected.
Symptoms should be confirmed diagnostically because nutrient problems, herbicide injury and other viruses can appear similar.
Begomoviruses
Begomoviruses are a large virus group containing many important whitefly-transmitted plant pathogens.
Depending on the virus and crop, symptoms may include:
- leaf curl
- yellow mosaic
- chlorotic patches
- distorted growth
- reduced leaf size
- stunting
- poor fruit production
The exact host range and symptoms vary between viruses.
How transmission occurs
A simplified transmission pathway is:
- A whitefly adult feeds on an infected plant.
- Virus is acquired during sap feeding.
- The virus passes through the insect internally.
- The adult moves to another plant.
- Virus is introduced while the insect feeds.
- The newly infected plant becomes another potential reservoir.
For persistently transmitted viruses, an infective adult may retain the virus for an extended period.
Virus transmission versus feeding damage
| Issue | Feeding damage | Virus transmission |
|---|---|---|
| Main cause | Sap removal and honeydew production | Feeding by an infective vector |
| Main signs | Yellowing, sticky leaves and sooty mould | Virus symptoms may appear later |
| Pest tolerance | Depends on crop and quality standards | Very low in vulnerable crops |
| Response | Whitefly suppression | Suppression plus plant-health action |
| Species importance | Several whitefly species | Particularly Bemisia tabaci |
A low whitefly population can still present significant risk where an important virus is present.
Virus reservoirs
Potential reservoirs include:
- infected crop plants
- symptomless hosts
- weeds
- volunteer plants
- old crop residues
- propagation stock
- neighbouring susceptible crops
Reservoir management is therefore part of virus prevention.
Propagation and incoming-plant risk
Propagation systems are vulnerable because:
- plants are young
- crops are closely spaced
- material moves between sites
- infection may occur before symptoms become clear
- adults can move rapidly through a compartment
Incoming plant material should be inspected, isolated where appropriate and sourced through reliable plant-health systems.
Prevention strategy
A strong whitefly-virus programme combines:
- clean propagation material
- exclusion and quarantine
- early species identification
- frequent lower-leaf inspections
- yellow sticky-trap monitoring
- rapid removal of suspect infected plants
- weed and reservoir management
- preventative biological control
- movement controls between production areas
- diagnostic and regulatory follow-up where required
Biological control
Biological control reduces whitefly pressure but does not cure infected plants.
Glasshouse whitefly
Tobacco or silverleaf whitefly
Long-season predator programmes
Programme choice depends on:
- whitefly species
- crop
- temperature
- crop duration
- pest density
- pesticide history
Key message
Where Bemisia tabaci or a whitefly-transmitted virus is suspected, the problem is not simply routine feeding damage.
Early identification, clean plant material, exclusion, reservoir management and appropriate plant-health action are essential.