Did you know?
A widespread common pest, whitefly can cause severe damage to a wide range of crops throughout the entire growing season.
The two most common species encountered in horticulture are greenhouse whitefly (Trialeurodes vaporariorum) and tobacco whitefly (Bemisia tabaci).
With piercing and sucking mouthparts, this pest has similar feeding behaviour to aphids – both are related to the Hemiptera order.
“In temperate regions, greenhouse whitefly can affect open field, as well as glasshouse-grown, crops,” says Biobest IPM and Pollination Specialist Sam Gui. “Meanwhile, Bemisia poses a serious threat to crops grown under artificial lighting. Highly resistant to insecticides, it is also capable of transmitting destructive plant viruses such as TYLCV – as well as causing physiological disorders such as TIR in tomatoes.”
Signs & symptoms
“Adult whitefly generally settle on the undersides of leaves towards the top of the plant,” explains Sam. “During scouting, it is a good idea to tap plant parts or pots as the adults tend to fly up becoming visible. However, in some crops – such as aubergine – the adults tend to be less inclined to take to their wings and are best scouted by turning over the leaves.”
Whitefly larvae require plenty of protein to grow and therefore consume large quantities of plant sap; this can impact on the plant physiology resulting in retarded growth.
“The sap feeding larvae and adults excrete a sticky suspension – called honeydew,” says Sam. “Often visible on fruits and leaves as a shiny deposit, it can feel sticky to touch.”
The presence of honeydew is another important indicator there is whitefly in the crop.
Often colonized by fungus (sooty mould), the honeydew turns black – compromising the plant’s ability to photosynthesise. In ornamental crops, the honeydew can reduce the aesthetic value of plants.
When scouting it is important to stay alert for symptoms of virus transmission.
Pest host range
Whitefly outbreaks can occur on most greenhouse crops – from ornamentals to vegetables. Control has become a significant part of IPM programmes for cut Gerberas, Poinsettias, pot roses, tomatoes and aubergines etc.
What does it look like?
For successful control, it is important to distinguish between these two widespread and important whitefly species. To do this, adults should be observed under a lens in the crop, or on a sticky trap.
For fast field observations, Sam recommends checking the following:
- When at rest, the wings of the adult Bemisia do not touch – revealing more of the abdomen when viewed from above.
- Adult Trialeurodes vaporariorum are whiter in comparison to Bemisia (yellower).
In general, whitefly eggs are very small – up to 0.2mm and oval in shape. When laid they are initially pale, turning darker within 2-3 days before hatching.
The immobile larvae grow by shedding skins and the pupae are around 0.7mm.
Greenhouse whitefly pupae are round, white, transparent and have an upright edge covered with waxy hairs. In contrast, Bemisia pupae are yellow, transparent, irregularly shaped and flat with no hairs.
Adult whitefly are 1-2mm long.
“Careful monitoring of plants and sticky traps – to observe the first appearance of the pest – is the cornerstone for making good IPM decisions,” says Sam.
“Biobest has a range of IPM tools in its portfolio to enable growers to successfully bring these two whitefly species under control. Programmes vary depending on the pest species, as well as factors such as population level and the crop. Our skilled team of technical advisers is on hand to help.”
- Parasitic wasp Encarsia Formosa parasitises whitefly larvae. (Encarsia-System)
- Green mirid bug Macrolophus caliginosus feeds on all stages of whitefly (Macrolophus-System)
- For southern European crops? – the bright green mirid bug Nesidiocoris tenuis also feeds on all whitefly stages (Nesidiocoris-System)
- Entomopathogenic fungi Isaria fumosoroseus parasitises all whitefly stages (Preferal®)
- The predatory mite Amblyseius swirskii feeds on whitefly eggs – as well as other pests (Swirskii-System & Swirskii-Breeding-System).
- The predatory beetle Delphastus catalinae feeds on all stages of whitefly (Delphastus-system)
Bug-Scan® yellow sticky traps and Bug-Scan® rolls for monitoring can also help reduce whitefly adults in the crop.