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Plantwise Technical Factsheet

whitefly, greenhouse (Trialeurodes vaporariorum)

Host plants / species affected
Actinidia chinensis (Chinese gooseberry)
Ageratina adenophora (Croftonweed)
Apium graveolens (celery)
Aster
Bouvardia
Brassica
Camellia sinensis (tea)
Capsicum (peppers)
Capsicum annuum (bell pepper)
Chenopodium giganteum (large lambsquarters)
Chrysanthemum (daisy)
Citrullus lanatus (watermelon)
Cucumis melo (melon)
Cucumis sativus (cucumber)
Cucurbita (pumpkin)
Cucurbita pepo (marrow)
Cucurbitaceae (cucurbits)
Cyphomandra betacea (tree tomato)
Euphorbia pulcherrima (poinsettia)
Fragaria (strawberry)
Freesia
Fuchsia
Gerbera (Barbeton daisy)
Gerbera jamesonii (African daisy)
Glycine max (soyabean)
Gossypium hirsutum (Bourbon cotton)
Helianthus annuus (sunflower)
Hibiscus rosa-sinensis (China-rose)
Impatiens (balsam)
Ipomoea (morning glory)
Lactuca sativa (lettuce)
Lantana camara (lantana)
Lycopersicon
Malva sylvestris
Nicotiana
Origanum majorana (sweet marjoram)
Pelargonium graveolens (Rose geranium)
Persea americana (avocado)
Phaseolus (beans)
Phaseolus vulgaris (common bean)
Psidium guajava (guava)
Rhododendron (Azalea)
Rosa (roses)
Rubus idaeus (raspberry)
Solanum lycopersicum (tomato)
Solanum melongena (aubergine)
Solanum tuberosum (potato)
Sonchus (Sowthistle)
Stellaria media (common chickweed)
Tagetes erecta (African marigold)
List of symptoms/signs
Fruit  -  honeydew or sooty mould
Inflorescence  -  honeydew or sooty mould
Leaves  -  abnormal colours
Leaves  -  abnormal forms
Leaves  -  necrotic areas
Stems  -  honeydew or sooty mould
Whole plant  -  dwarfing
Description
Eggs

Eggs are approximately conical in shape, yellowish-white turning to purplish grey after 2 days and 0.25 mm long. They are oviposited on a short pedicel, which is inserted in epidermal cells on the lower leaf surface, often in a circle or a crescent.

Nymphs

Nymphs or 'crawlers' are usually pale green, but can also range from yellow to dark brown. They are oval, flat and resemble scale insects. There are four or possibly five leg segments and two to three antennal segments. Segmentation is not clear and most specimens will appear to have only three leg segments and two antennal segments. Small amounts of powdery white wax are usually produced after the crawler settles and begins feeding. The first nymph is mobile, whereas later nymphal stages are immobile. They resemble soft scale insects, but have a vasiform orifice on the back through which honeydew is expelled. There are four nymphal stages with the final stage beginning as a feeding nymph before it becomes a pupa. The final larval stage begins as a flat translucent disc, but as it develops through to the pupa a waxy fringe begins to develop around the margin. As this grows, the larva becomes more 'pork pie' shaped.

Pupae

The pupa is the final stage of the fourth nymphal instar and is assumed to be at the point where the nymph stops feeding and apolysis begins. The pupa becomes a milky-yellow colour and, as the adult develops within, red eyes become visible through the cuticle. The marginal fringe, which is formed from many fused wax rods, is very obvious at this stage. Downward curving wax setae are also visible all around the edge of the marginal plain. On hirsute leaves, the pupae often develop long, waxy setae on the dorsal surface. These are not always present on pupae that have developed on glabrous leaves.

Adults

Adults are about 1.5 mm long, white and resemble tiny moths. The wings are pale yellow, held relatively flat when in repose and are coated with a pure white waxy bloom.
Prevention and control

Cultural Control

It is important to ensure that plants are not infested with T. vaporariorum before being taken into the glasshouse. This is equally as important when whitefly populations are already present in the glasshouse, due to the risk of introducing novel insecticide resistant strains. A suitable insecticide can be applied as a routine precaution. Recent studies have demonstrated the effectiveness of UV absorbent plastic films at reducing T. vaporariorum infestations on protected crops (Mutwiwa et al., 2005).

Biological Control

Biological control has been widely used in glasshouses, especially since the development of insecticide-resistant whiteflies, and is chiefly based on the chalcid wasp Encarsia formosa and entomopathogenic fungi (Osborne and Landa, 1992).

E. formosa parasitizes T. vaporariorum, each female being capable of laying 50-200 eggs during its lifespan of 10-14 days. Each egg is inserted into advanced nymphal stages which are subsequently killed. Scales containing parasites are highly visible because they are black. Successful control can be obtained if the parasite is established on plants when natural infestations are small. The parasitoid is usually shipped as parasitized scales on strips. For cucumbers, a typical rate of release is 12,500 parasitoids per ha in areas where T. vaporariorum is a habitual pest, starting at the beginning of the season. In tomato, most growers introduce parasitized scales weekly at the rate of 5000/ha as soon as plants are available. Once the parasitoid is established, it is important to avoid removing from the glasshouse leaves with black scales from which adult wasps have not emerged. Empty scales can be spotted by holding leaves up to the light and examining them for emergence holes (Sprau, 1990; Lynch and Johnson, 1991; Ruisinger and Backhaus, 1994; van Lenteren et al., 1996; van Roermund et al., 1997).

The predatory beetle Delphastus pusillus is very effective against greenhouse and sweet potato whitefly (Bemisia tabaci). Both the larval and adult beetles feed on all stages of T. vaporariorum and will eat spider mites when whitefly are not available.

Lacewings (species of Chrysoperla) are also used as general predators of glasshouse pests and will consume whiteflies.

The fungal pathogen Verticillium lecanii attacks whiteflies and thrips and can be a useful control agent in situations where the crop is grown in high humidities (Masuda and Kikuchi, 1993). The disease attacks young as well as adults, taking about 1-2 weeks to develop. Commercial preparations are available (Ravensburg et al., 1990, 1993). Microbial insecticides based on the entomopathogenic fungus Paecilomyces fumosoroseus have also been used for the control of T. vaporariorum (Bolckmans et al., 1995; Sterk et al., 1996).

Host-Plant Resistance

Soria et al. (1996) showed the participation of both antixenosis and antibiosis resistance mechanisms against T. vaporariorum in an accession of melon (C. melo var. agrestis). Lambert et al. (1995) investigated possible resistance mechanisms in soyabean and discovered that trichome erectness was a factor. Cultivars supporting lower whitefly populations had higher erectness ratings (trichomes flat on leaf surface) than accessions with higher whitefly populations. An investigation of epicuticular lipid composition also revealed that soyabean accessions with low levels of luteol were more susceptible to whitefly colonization (both T. vaporariorum and Bemisia tabaci).

Chemical Control

Due to the variable regulations around (de-)registration of pesticides, we are for the moment not including any specific chemical control recommendations. For further information, we recommend you visit the following resources:


Impact

Whiteflies damage plants directly by sucking sap from leaves and indirectly by transmitting viruses and producing a sticky secretion known as honeydew, which prevents crops from functioning normally, as well as acting as a substrate for fungal growth (sooty moulds).

Whitefly adults and nymphs feed by inserting their proboscis into the leaf, penetrating the phloem or nutrient conducting vessels and withdrawing sap. As it feeds, the whitefly injects saliva into plant tissues. Whitefly feeding removes nutrients from the plant which may result in stunting, poor growth, defoliation, reduced yields and even death in extreme cases. The extent of damage caused by feeding is generally directly proportional to the whitefly population and low populations rarely have much impact. On certain plants, stunting or abnormal coloration can be caused due to the physiological stress of the feeding. Plants stressed by the removal of sap due to heavy whitefly feeding may require more irrigation.

Whiteflies secrete significant quantities of honeydew as they feed. When populations of whiteflies are high, honeydew production can be copious, dripping down leaves onto fruit. Honeydew becomes a serious problem when it is colonized by black, sooty mould fungi, blackening leaf or fruit surfaces. This can render fruit unmarketable and block out sunlight, inhibiting photosynthesis.

T. vaporariorum became an economical important insect pest of greenhouse vegetable and ornamental crops in the middle 1970s in Beijing, China. More recently, it has become a serious horticultural pest within areas of southern Europe, where an increase in the incidence of Tomato chlorosis virus may be attributed to it. Within the UK, insecticide resistance has led to increased problems for growers of shrubs such as Ceanothus and soft fruit crops such as strawberries.

Virus transmission

The piercing and sucking mouthparts of T. vaporariorum provide an excellent mode for transmitting disease-causing viruses from one plant to another. As immature stages do not move on to new plants, virus transmission is a concern only with adult whiteflies.

Some of the more important viruses spread by T. vaporariorum are Beet pseudo-yellows virus (cucumbers, melons, lettuces and sugarbeet), Tomato infectious chlorosis virus and Lettuce infectious yellow virus. Further viruses are being identified and characterized which include Strawberry pallidosis virus (Tzanetakis et al., 2004).

Related treatment support
Pest Management Decision Guides
Shoufu, D.; Shihua, L.; Guoyin, S.; CABI, 2013, Chinese language
Chen, L.; Han, Z. L.; CABI, 2016, English language
Kiritai, S.; Kagai, K.; Otipa, M.; Ngigi, B.; Kilalo, D.; Macharia, E.; Ndung'u, B. N.; CABI, 2013, Swahili language
Chen, L.; Han, Z. L.; CABI, 2016, Chinese language
CABI; CABI, 2018, English language
 
External factsheets
Bayer CropScience Crop Compendium, Bayer CropScience, English language
East West Seed Insect Pest Factsheets, East West Seed, 2013, English language
IVIA factsheets, Instituto valenciano de investigaciones agrarias, Spain, 2015, Spanish language
Plant Health Australia Factsheets, Plant Health Australia, English language
RHS Gardening Advice Factsheets, Royal Horticultural Society, English language
Video factsheets
Koppert Pest Control videos, Koppert Biological Systems, 2016, English language
Koppert Pest Control videos, Koppert Biological Systems, 2016, English language
Koppert Pest Control videos, Koppert Biological Systems, 2016, English language
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