Overview
What are Whiteflies?
What are the different types of Whitefly?
What is the impact of Whiteflies?
How do I know if I have a Whitefly problem?
How do I get rid of Whiteflies?
Conclusion and future direction
Whiteflies are a collection of species of small white insects that can damage crops by feeding directly on crop fluids.
The insects affect a wide range of plants, including trees, ornamental plants, vegetables, and fruits. Whiteflies are found worldwide, although different species are more prevalent in certain areas.
These bugs are easy to identify, and there are several effective strategies for prevention and control such as biocontrol products, or yellow sticky traps, and reflective mulch.
This article discusses the essentials for identifying and dealing with whitefly infestations. Let’s begin with a general overview of whiteflies, focusing on identifying them effectively.
What are Whiteflies?
Whiteflies are small white or yellow insects that can cause damage to crops. These bugs have wings and can fly but are not considered true flies. In fact, they are more closely related to other insects like aphids, and their white color comes from a waxy substance that covers the bodies and wings of adults.
Adult whiteflies are white or yellow, triangle-shaped, and grow to around 1.5 – 3mm. They are active during the day and feed by sucking fluids from crops.
Adult whiteflies lay their eggs on the underside of leaves. Once the oval-shaped pale-yellow eggs hatch, immature whiteflies progress through four nymphal stages known as instars, and nymphs vary in color depending on the species. Whiteflies feed on crop sap throughout their development and adulthood and secrete a sticky substance called honeydew.
Whiteflies typically live on the underside of new leaves and might appear like dust if a leaf with a large colony is disturbed.
What are the different types of Whitefly?
There are hundreds of whitefly species, though only a handful cause damage to crops. Below is an overview of the most common problem species.
Silverleaf Whitefly (Bemisia tabaci)
The precise geographic origin of this species is not known, though it may have originated in India. It now has a wide geographical distribution and is also known as the tobacco whitefly or sweet potato whitefly. Adults are around 1mm long, are white or yellow, and have a vertical tilt to their wings. It feeds on many crops like tomatoes and beans, but also grain crops.
Greenhouse Whitefly (Trialeurodes vaporariorum)
This species is considered a global pest and is problematic in India. Greenhouse whiteflies feed on various crops, including vegetables, and adults are typically 1.5mm in size, white, and considered moth-like in appearance.
Ash Whitefly (Siphoninus phillyreae)
As the name suggests, these whiteflies feed on ash trees but also on other broadleaved trees and fruit trees, such as pomegranate. Ash whiteflies are native to India and Eurasia but are now found globally, including in North America, where they are considered pests. Adults are white with a somewhat translucent appearance, range from 1mm to 2mm in length, and look similar to greenhouse whiteflies.
Carmelo Rapisarda
Giant Whitefly (Aleurodicus dugesii)
This species can grow to around 5mm in length, making it one of the largest types of whiteflies. Besides its size, it can be distinguished from other whitefly species by the spiraling wax deposits of adults. Giant whiteflies have yellow bodies and white wings and feed on a diverse range of crops. Native to Mexico, this insect is now found throughout the USA, including Hawaii.
What is the impact of Whiteflies?
Whiteflies cause damage by feeding on sap from crops directly. They possess needle-like mouthparts, which allow them to penetrate crop tissue and gain access to the sap, the liquid that carries food for crops. Large quantities of whiteflies can deplete crop nutrients and cause leaf yellowing. This results in stunted growth, and premature leaf drop-off. They also secrete honeydew onto the surface of crops, which promotes the growth of black sooty mold caused by fungi. Whiteflies also transmit hundreds of plant viruses and can significantly reduce the yield of vegetable crops. These viruses, such as the tomato infectious chlorosis virus, can lead to massive drop-offs in crop yield. Fruit crops are less likely to be affected by whiteflies, with the exception of citrus fruit.
Are Whiteflies dangerous to humans?
No. There is no evidence to suggest that whiteflies pose any threat to humans.
How do I know if I have a Whitefly problem?
Whiteflies are active during the day. This, in addition to their color, makes them far easier to spot than other pests. Checking for early signs of whiteflies is as simple as examining the underside of leaves and looking for these small yellow/white insects.
Larger infestations are even easier to detect. If a leaf that houses a significant colony of whiteflies is disturbed, a large cloud of adult whiteflies will take flight before eventually returning to their leaves. Another tell-tale sign of a large infestation is the presence of honeydew and black sooty mold on the surface of leaves.
How do I get rid of Whiteflies?
Cultural control
Like with many pest infestations, prevention methods are a crucial first step to keeping crops free of whiteflies. Providing adequate spacing and irrigation for crops and removing weeds and dead plant material can prevent whitefly infestations.
If you discover that you have a whitefly problem, there are several effective methods for dealing with it.
Biological control
Natural predators and pathogens provide an effective and safe way to reduce the number of pests in farms.
Augmentative biological control involves releasing natural predators or pathogens that decrease the number of pests in the environment. This can be done by using biological control solutions, such as entomopathogenic fungi like Isaria fumosorosea or natural substances like neem oil. You can also release invertebrate biocontrol agents, including parasitoids like Encarsia formosa, or predators like the ladybird Delphastus catalinae or the predatory mite Amblyseius swirskii.
Conservation biological control methods involve creating an environment that fosters the growth of natural enemy populations. This concerns natural enemies that are already present in the environment, but also biocontrol agents that are released for control purposes. This is typically a longer-term solution that works well with augmentative biocontrol. Conservation biological control can include cultural methods such as providing food sources and shelter for predators.
Dispersal
Water hoses can be a great way to disperse whitefly colonies, and cutting away heavily infested leaves can directly reduce whitefly numbers without damaging your crop. Just make sure to dispose of them carefully.
Yellow sticky traps
These traps are simple to set up and effective for monitoring and controlling whitefly populations. An equal mixture of petroleum jelly and dishwashing detergent on strategically placed yellow cards can help prevent whiteflies from damaging your crops.
Reflective mulch
Placing reflective mulch around vegetables early in the season can prevent whiteflies from identifying and colonizing host crops such as tomatoes and peppers. Mulch is also effective against other pests.
Chemical control
Any chemical control strategies should be used with caution and as a last resort. Chemicals can deplete the populations of whitefly natural enemies and may accidentally create a niche for whiteflies to grow. This is in addition to the potential damage to plants and the environment that chemicals can cause. There are several chemical control options for whiteflies. For more information, you can read this review article which includes a discussion of insecticides to tackle whiteflies.
Conclusion and future direction
Whiteflies are significant pests that affect a broad spectrum of crops in a wide geographical range. These bugs cause damage to crops through sap-feeding, the secretion of honeydew, and the transmission of plant viruses. While there are many species of whitefly, similar control strategies can tackle all of them effectively.
Fortunately, these pests are easy to identify, and several simple prevention measures can keep their populations under control. Biopesticides and biocontrol agents, dispersal with water hoses, yellow sticky traps, reflective mulch, and encouraging natural enemies can all be effective, while chemical control is best used as a last resort. Balancing control measures with environmental considerations ensures sustainable practices, protecting crop health and the surrounding ecosystem.
For more information on different types of pests, visit the CABI BioProtection Portal resources. To help find the best solution for your whitefly problem, visit our products page.
