Whitefly is one of the world’s most widespread garden and greenhouse pests. These tiny insects are infamous for their devastating effects on crops, where their sap-sucking feeding habits can cause widespread damage. Whitefly is also notorious vectors for plant viruses and can transmit all sorts of nasty diseases to your plants, causing stunting, leaf dropping, reduced yield and, in extreme cases, plant death.
Once established, a whitefly infestation can be very difficult to get rid of. These bugs breed rapidly and are resistant to most insecticides, so eliminating them can be a lengthy and often frustrating process.
So, how can you deal with whitefly in your garden? Where are they most likely to be found, when are they most active and, most importantly, how can you kill them? Prevention and integrated pest control are the best ways to stop whitefly from taking over your plants. Read on for the most effective control methods and how to use them at home, so you can be rid of whiteflies once and for all!
Whitefly infestation and damage
Naturally, whitefly infestation will lead to plant damage at one point. This can be avoided if the infestation is stopped early enough. However, to fight the problem, you must recognize it first.
How can you tell if you have whiteflies?
Identifying a whitefly infestation is easy if you know what to look for! First, make a visual inspection of your plants. Whiteflies feed on the underside of leaves, so this is where they’re most likely to be found. Check the bottom of leaves for adults (which look like tiny, white moths), eggs (often arranged in neat circles) and larvae (which look like white, oval scales).
Another way to check for the presence of whiteflies is with yellow sticky pads. These glue traps can be placed near plants, where they will capture any whiteflies that venture nearby. You can also give the stems of plants a firm shake – if they are heavily infested, you’ll see a cloud of white flying bugs rise off your plants before settling back on the leaves.
Another way to identify a whitefly problem is to be on the lookout for sooty mold. The sticky honeydew secreted by whitefly encourages the growth of this fungus, which has a distinctively dark, patchy appearance. In extreme cases, this can cover large areas of leaves.
Whitefly feeding also causes visible signs of damage. These sap-suckers can give leaves a mottled appearance and cause yellowing, chlorotic spots, wilting and stunting of plants, premature leaf dropping and even death.
Common host plants
Whitefly feed on a wide array of plants. Some species (such as the Greenhouse whitefly) are particularly prolific, with a host range of over 250 plants. Whitefly is especially fond of ornamentals and vegetable plants such as tomatoes, cucumbers, roses, poinsettia, hibiscus, squash, begonia, and citrus.
Damage to plants
Whitefly can cause significant damage to crops, vegetables, and ornamental plants, especially when present in large numbers. Much of the damage caused by whitefly is due to the way they feed. These sap-sucking insects drill into the phloem of plants to drain their nutrients, causing yellowing of the leaves, mottling, wilting, stunting and premature dropping of leaves. In extreme cases, a heavy whitefly infestation can even lead to plant death.
Whitefly is also notorious plant virus vectors and can transmit a wide range of diseases to vegetables and ornamental plants. Many of these, such as the Tomato yellow leaf curl virus, can devastate crops, causing stunted growth, yellowing of leaves and drastically reduced fruit yield.
Whitefly also produces honeydew, a sticky substance that they secrete as they feed. This falls onto the foliage around them where it encourages the growth of sooty mold, a dark-colored fungus that grows on the leaves of plants. This unsightly mold not only makes plants less attractive but, in extreme cases, can prevent sunlight from reaching the leaves.
Honeydew also attracts ants. The sweet, sugary residue left behind by whiteflies is a valuable food resource for ants and, as a result, these insects often live side by side with whiteflies. Unfortunately, ants also attack other insects, including predatory and parasitoid species that would usually feed on whiteflies. In doing so, they protect the whitefly population, allowing them to feed and breed undisturbed by natural enemies.
In cases of heavy infestation, the damage caused by whiteflies can be devastating. Large numbers of whitefly can cause stunted growth, reduced fruit yield and premature death of plants. Preventing an infestation from taking hold is, therefore, crucial if you are to protect your garden and greenhouse from these voracious pests.
Even though many people have been troubled by whiteflies, and even more have seen or at least heard about them. Yet, most people don’t really know much on the subject. Knowing a thing or two about whiteflies can be not only interesting but also come in handy in case there ever is a need to get rid of these beings.
What are whiteflies?
Whiteflies, despite their name, are not true flies. In fact, they are more closely related to aphids, scales, and mealybugs; sap-sucking insects that drain plants of their nutrients as they feed. There are many different species of whitefly, many of which look very similar to one another. These tiny, white flying bugs are typically moth-like in appearance, and adults are rarely more than a few millimeters long.
Whitefly is fast breeders, and infestations can take hold in no time at all! Female whiteflies can produce up to 300 eggs at a time, which they lay on the underside of leaves. After 4 – 12 days, the tiny, white, oval eggs hatch into the first of four instars. The first instar, called the ‘crawler’, walks around on the underside of the leaf until it finds a place to feed. Once they settle down, nymphs lose their ability to walk and will stay in the same spot for the rest of their development. Later instars look like tiny, flattened scale-like insects without legs or antennae.
Whitefly nymphs get gradually larger as they progress through the four instar stages until they pupate. Finally, they emerge as winged, moth-like adults. The entire whitefly lifecycle takes 14 – 60 days, depending on temperature. Under ideal conditions (around 80 F), they will reach adulthood in around 3 weeks.
Whitefly love warm climates and, as such, are most commonly seen in mid-late summer. They are most active during the daytime, when the air temperature is warm, and are often found in greenhouses. In southern states (such as Southern California, Texas, South Carolina and Arizona), they can overwinter outdoors. They are unable to survive year-round in places with harsh winters, however – though they may hide out in greenhouses until summer comes around again.
Most common whitefly species
Whitefly is a global problem, with over 1500 species worldwide. The most common (and troublesome) species are:
- Ash whitefly (Siphoninus phillyreae)
- Giant whitefly (Aleurodicus dugesii)
- Greenhouse whitefly (Trialeurodes vaporariorum)
- Citrus whitefly (Dialeurodes citri)
- Silverleaf whitefly (AKA Sweetpotato whitefly) (Bemisa tabaci)
- Bandedwinged whitefly (Trialeurodes abutiloneus)
Once established, whitefly infestations can be difficult to control. Many species are resistant to a wide range of insecticides, and ridding your garden, greenhouse and houseplants of these pests can often feel like an uphill struggle. How you manage your whitefly invasion will depend heavily on the scale of the problem and where they are located.
Whitefly control methods
Multiple control methods are often required to tackle whitefly at every developmental stage, and preventative measures should also be put in place. This includes spraying, vacuuming and even cutting the plants in question. Of course, all these methods have their own strengths and flaws, which will be discussed further on.
Spray them away
One very simple method of controlling a whitefly infestation is to physically remove them. This can be done with a strong blast of water from a high-pressure hose. Direct the jet onto the undersides of leaves, as this is where whitefly feed and, therefore, are most commonly found. This method has the benefit of being entirely organic and will not disrupt the ecosystem of your garden in any way. It’s also very easy to do, and very inexpensive!
For best results, you will need to use a high-pressure jet of water. Adult whitefly is easily displaced, but the nymphs (tiny, scale-like creatures) cling tightly to leaves and will be able to hold on if the jet is not strong enough.
This method must also be repeated regularly (at least once a week) for the best results and should be used alongside other control methods. Although water-blasting whitefly can work well for controlling smaller infestations, it may not be as effective for tackling large numbers of the insects. This method is best used on outdoor plants, for obvious reasons.
Spray method is Best for: Removing adults, eggs, and nymphs from outdoor plants.
- Highly effective when used as part of integrated pest management
- Organic and non-toxic
- Easy to do
- May not kill whitefly
- May not remove all whitefly from plants
- Must be repeated regularly for best results
Another easy way to remove whitefly from plants is by vacuuming. Simply take a small, hand-held vacuum and use this to suck adult whitefly right off the leaves! Make sure you focus on the undersides of leaves, where whitefly spends most of their time. The best time of day to do this is in the evening or early morning when the cooler temperature will make whitefly sluggish and easier to capture.
Afterward, it is important to dispose of the whitefly properly, so they don’t escape the vacuum bag and find their way back to your plants. Placing the bag in the freezer overnight will kill the whitefly, after which you can simply dispose of the bag in the trash. This method can be used to remove substantial numbers of whitefly from your plants, effectively reducing the size of your infestation. As this method removes adult whitefly, it also disrupts their breeding cycle and reduces egg production.
As with water-spraying, this method must be repeated at least once a week and should be used as part of an integrated pest management effort. Although vacuuming is an effective way to physically remove adult whitefly, it may not be as effective at removing nymphs. This is because the nymphs hold on tightly to leaves and are not as easily displaced.
This method can be used to control minor whitefly infestations on houseplants and in greenhouses. In the case of large infestations, more drastic control measures will need to be implemented – especially if you have lots of nymphs.
Vacuuming method is Best for: Removing adult whitefly from indoor and greenhouse plants.
- Organic and non-toxic
- Effectively removes large numbers of adult whitefly
- Easy to do and inexpensive
- Can kill whitefly
- Must be repeated weekly
- May not remove whitefly nymphs
Cutting infested plants
Cutting or pruning the leaves of heavily infested plants is another effective way of reducing a whitefly infestation. This method can be used to tackle eggs and nymphs, which cling tightly to the leaves and can be difficult to remove by vacuuming or spraying with water.
Carefully inspect your plants to establish which ones are infested. Nymphs tend to congregate on the lower leaves of plants, so these are the areas you should target when cutting. Lower leaves are also more difficult to reach with sprays and may be overlooked during whitefly treatment. They are, therefore, a common refuge for whiteflies.
Trimming and removing these leaves can be very helpful when trying to get a whitefly infestation under control. Once you’ve removed the leaves, dispose of them in a way that kills the eggs and nymphs. This can be done by burning, burying the leaves deeply underground, or placing them in black, plastic refuse sacks and leaving them out in the sun for a few weeks.
Cutting and trimming should be used as part of an integrated pest management plan for the best results. Although it is an effective way of reducing whitefly numbers and is a good way to tackle eggs and nymphs, it cannot completely eradicate a whitefly infestation. It is also important not to remove too many leaves when trimming, as this can do more harm to your plants than good.
Infested plant cutting method is Best for: Removing eggs and nymphs from heavily infested plants.
- Easy to do
- An effective way of tackling whitefly eggs and nymphs
- Will not completely eradicate whiteflies
- Does not target adult whiteflies
- Over-trimming can harm the health of your plants
Whitefly control products
Whitefly control doesn’t stop with just the methods mentioned previously. There is also a wide variety of products that can be used to deal with the situation. This not only includes different types of sprays and traps but also some very natural options, as well as natural predators. Just like the methods discussed before, products also have their pros and cons.
Yellow sticky traps
Adult whiteflies are strongly attracted to yellow, so yellow sticky traps are a great way to start your war on whiteflies. These can be used to both capture and monitor the insects. If you find whiteflies in your garden, greenhouse or on houseplants, buy or make several sticky traps and place them near your plants. The whitefly will be drawn to the traps and land on them, where they will become stuck in the glue and die.
Yellow sticky traps can catch a great number of whiteflies, significantly reducing the size of your infestation. By removing a large proportion of adult whitefly from your plants, you can also limit the number of eggs that are laid on the leaves. This further reduces the population by interrupting the breeding cycle.
Yellow sticky traps are also a valuable monitoring tool. The number of whiteflies caught on your traps will give a good indication of the size of the infestation, and whether it is getting smaller. They should, therefore, be used throughout the control period so you can keep tabs on your whitefly population. Even after the infestation has been eradicated, sticky traps should be kept in place, so you can tell instantly if the whitefly has returned.
Yellow sticky traps are Best for: Removing large numbers of adult whitefly from plants and monitoring whitefly populations.
- Easy to implement
- Low maintenance
- A highly effective way of removing large numbers of adult whitefly
- Disrupts breeding cycle so fewer eggs are produced
- Effective monitoring method
- Will not completely eradicate a whitefly infestation – must be used as part of integrated pest management
Whitefly has several natural enemies that can be recruited to help fight infestations.
Predatory insects such as ladybug beetles, parasitic wasps, and predatory mites are all effective whitefly killers. The parasitoid wasp, Encarsia formosa, is widely used as a successful biological control measure against whitefly. These tiny bugs can be bought in bulk and released in greenhouses, where they attack and kill Greenhouse whitefly. This can significantly reduce the number of whiteflies on tomatoes, cucumbers, peppers, and eggplants.
These aggressive (but non-stinging) wasps are attracted to whitefly by the scent of the honeydew they produce. Once they track down their target, they lay eggs inside the 2 – 4th nymph stages of the whitefly. The resultant larvae grow inside the whitefly, weakening and killing their prey from within. Eventually, they will chew their way free of the whitefly’s body to emerge as fully-grown adults. A single female wasp can kill up to 95 whiteflies over her 12-day lifespan, making these parasitoids a highly effective means of reducing whitefly numbers.
Encarsia formosa work best in warm, humid conditions, so they are most suitable for use in greenhouses. Cooler temperatures will inhibit reproduction and development of these wasps – in fact, they are unable to fly below temperatures of 62F.
Whitefly predators are Best for: Tackling whitefly infestations in greenhouses and areas with warmer climates.
- Sustainable, natural, non-toxic means of biocontrol
- Easy to use
- An effective way to kill large numbers of whitefly
- May be unsuitable for outdoor use
- Wasps need specific temperature, humidity, and lighting conditions to function effectively
Organic whitefly sprays
Organic sprays for whiteflies can be one of the most environmentally friendly and inexpensive ways to tackle a whitefly infestation. These sprays are highly effective natural whitefly killers, though they have limited toxicity in mammals and other, beneficial insect species. They are also biodegradable, don’t persist in the environment, and are suitable for use on both edible and indoor plants.
However, these contact killers must be sprayed directly onto the insects for them to have any effect. This means they must be applied repeatedly and regularly, which can be time-consuming if you have lots of plants to treat.
Insecticidal soaps can be a valuable tool in your war on whitefly. Not only do they effectively kill pests on greenhouse, garden and house plants, but they also have very few adverse effects on the environment.
Insecticidal soaps are potassium salts of fatty acids. They work by first breaking down the coating on outside of the whitefly’s body. Next, they disrupt the structure of the insect’s cell membrane, damaging the cell and causing the insect to die. These sprays are most effective on soft-bodied insects, such as whiteflies, aphids, and mealybugs. However, they are far less effective on hard-bodied insects, such as beetles. Therefore, beneficial predatory insects (such as ladybugs) are safe from harm. Insecticidal soaps also have low toxicity in mammals, making them safe to use even in households with children and pets.
What’s more, these formulations are biodegradable, do not linger in the environment, and leave no residue on plants. This makes them suitable for use even on edible plants such as tomatoes, cucumbers, and strawberries.
Unfortunately, insecticidal soaps are not effective against whitefly eggs. They are also contacting killers, meaning they must be sprayed directly onto the insect for them to have any effect. This means they must be applied regularly if they are to reduce your whitefly infestation effectively.
Neem oil (and other essential oils)
Various essential oils, such as neem, thyme, patchouli, lemon-scented gum, and geranium can also be used to kill whitefly. Insecticidal sprays containing these extracts are generally non-toxic to plants, mammals and beneficial insect species, such as ladybugs and honeybees.
Of these, neem oil is widely considered to be the most effective against whitefly.
Neem oil affects whitefly in several different ways. This insect growth regulator is most effective against immature nymphs, disrupting their development and killing them before they reach adulthood. It may also coat the insect’s body, covering their breathing holes and causing them to suffocate. Finally, it may act as a repellent, preventing adult whitefly from landing on plants or laying their eggs on the leaves.
Given its limited toxicity in humans and other animals, neem oil is especially useful for tackling whitefly on indoor house plants. It is also biodegradable and doesn’t persist in the environment, making it one of the best sprays for whiteflies. Its non-toxic nature also means that it is safe to use on edible plants.
Like other organic whitefly sprays, essential oils are contact killers. Therefore, they must be reapplied frequently for optimal effectiveness.
DIY whitefly sprays
One of the easiest ways to attack whitefly is to whip up your own anti-whitefly spray. A home remedy for whiteflies on plants can be concocted from everyday household ingredients and are an inexpensive way to kill whitefly in greenhouses, gardens and on house plants.
To make your own homemade whitefly spray, simply mix 1 tablespoon of regular dish soap with 1 cup of vegetable oil. Next, dilute your mixture by mixing 1 or 2 teaspoons of it with a cup of water. Remember, oil and water do not combine, so the solution must be shaken vigorously and frequently during spraying.
The soap in your DIY spray will kill whitefly in the same way as other insecticidal soaps; by removing their protective outer cuticle and damaging the cell membranes beneath. The oil will help it to stick, allowing the solution to thoroughly coat the insect’s bodies.
This control method is not only effective, but it is also very inexpensive and will have minimal impact on the surrounding environment. DIY sprays such as this one also have little to no toxicity in mammals or other, beneficial insect species (such as bees and ladybugs).
However, it must make direct contact with whiteflies for it to have any effect and must be applied to plants repeatedly and regularly.
Organic whitefly sprays are Best for: Treating small whitefly infestations on house plants and in greenhouses, and in households with children and pets.
- Natural and non-toxic
- Biodegradable and environmentally friendly
- Suitable for use on edible plants and house plants
- Effectively kill whitefly
- Easy to use
- Only kills with direct contact
- Must be reapplied regularly
Systemic whitefly insecticides
Systemic insecticides are often applied either as a soil drench or foliar spray. They differ from other pesticides in that they do not kill whiteflies immediately; instead, they are taken up and distributed throughout the tissues of the plant over a period of weeks. Once absorbed into the leaves, they quickly kill any insect that nibbles on them.
Systemic insecticides such as imidacloprid are some of the best whitefly killers around and can be used to tackle even large infestations. They are also popular as a low-maintenance pest control option, as they only need to be applied once a year. Imidacloprid may be the best insecticide for whiteflies; however, it is not necessarily a good idea to use it in your garden.
The impact of systemic insecticides on the surrounding environment can be problematic, especially when applied as a foliar spray or as a soil application in flowering plants. These insecticides are non-specific and will kill any insect that encounters with them, which is bad news for beneficial insect species like honeybees. It can also have a negative impact on predatory insect species, such as ladybugs and parasitoid wasps. Annihilating natural enemies in your garden can ultimately lead to a whitefly resurgence down the line, or even an outbreak of other pests, such as spider mites.
Aside from disrupting the ecosystem of your garden, systemic insecticides may also render your tomatoes inedible. As the whitefly pesticide is absorbed by the plant, it cannot be washed off or peeled away with the skin. Therefore, it shouldn’t be used on fruits or vegetables.
Systemic whitefly insecticides are Best for: Tackling large, persistent whitefly infestations of outdoor shrubs.
- Effectively kills whitefly
- Quick and easy to apply
- Long-lasting effects – no need for frequent reapplication
- Kills predatory insect species
- Kills pollinators
- Mildly toxic to mammals
- Not suitable for use on edible plants
Insecticides are not generally recommended for use against whiteflies, as many species are resistant to the chemicals. Traditionally, pesticides have been used extensively to control these pests with the result that, today, many of them are no longer effective.
Not only are insecticides unlikely to get rid of your whiteflies, but heavy use of these chemicals can also have adverse effects on the surrounding environment. They might not kill your target pest, but they may wipe out populations of other, more useful insects. Spiders, honeybees and predatory mites are among the beneficial insect species that can suffer from the use of insecticides in your garden. Removing natural whitefly enemies, such as parasitoid wasps and ladybugs, will only help your whitefly population to thrive.
The toxicity of insecticides also makes them more dangerous than most other methods of whitefly pest control. These chemicals can be very harmful if swallowed or inhaled and contact with the skin can cause irritation. Children, pets, and wildlife are especially vulnerable to these hazards, so insecticides are often unsafe to use at home. Whitefly chemical control is, therefore, not generally recommended for use in greenhouses and gardens.
- Some insecticides may effectively control large whitefly infestations
- Most whitefly species are resistant to insecticides
- Unsuitable for home use (especially in households with pets and kids)
- Environmentally unsafe
- May kill beneficial insect species
- May harm wildlife
- Can be difficult to dispose of
- Repeated treatment necessary
Pest control companies
If your whitefly situation is out of control, you may need to call in professional help to get rid of them. Large, well-established whitefly infestations can be a nightmare to deal with, especially if the problem is widespread. The persistent pests often require multiple control methods and repeated treatment to eliminate, due to their rapid reproduction rate.
If you are fighting a losing battle against whitefly, calling in a pest control expert may be your best option. An experienced technician will be able to quickly assess the situation and put together an integrated pest management plan to tackle your infestation.
How to prevent whiteflies
Prevention is the number 1 method for whitefly control. Once a whitefly infestation becomes established, their numbers can boom, making them very difficult to control. But how can you stop whitefly from taking over your plants?
Inspect plants regularly
Inspect plants in your house, garden, and greenhouse regularly for signs of whiteflies, especially during summer months when they are most active. Pay particular attention to the underside of leaves, as this is where whitefly feed and lay their eggs. Check for signs of feeding, such as yellowing or mottling of leaves, and be on the lookout for adults and larvae. Look for little white bugs on your plants, circular patches of eggs and tiny, white, scale-like larvae. Giving the stems of plants a firm shake can be a good way to tell if you have whitefly. If there are adult insects on your plants, they will rise up in a cloud when the leaves are disturbed. Inspect your plants regularly (at least once a week), and thoroughly. Remember, these insets are tiny and may be difficult to spot!
Inspect new plants before bringing them into your garden.
Always inspect plants thoroughly for whiteflies before bringing them home to avoid introducing an infestation. It may be a good idea to keep new plants away from your greenhouse for at least a week to be sure they are not harboring insects.
Protect natural predators
Natural predators are your friends when it comes to avoiding whitefly infestations. Avoid using insecticides that could potentially harm ladybugs, parasitic wasps or predatory mites. You may also want to consider releasing natural predators in your greenhouse as a preventative measure against these insects.
Monitor your plants
Monitoring methods can be a valuable tool when trying to prevent a whitefly infestation from taking hold. Yellow sticky whitefly traps are an effective and inexpensive way of keeping an eye on whiteflies. Simply place them near your plants to capture any nearby whiteflies. This can quickly alert you to the presence of whiteflies in your garden or greenhouse.
Scattering plastic, reflective mulches around the base of your plants can be an effective way to keep whiteflies at bay. The light reflected from these mulches can confuse whiteflies, preventing them from landing on your plants. If they cannot find their way onto your plants, they can’t feed and breed there! Synthetic mulches are not only an effective preventative tool, but they can also help to reduce whitefly numbers, preventing large infestations from becoming established.
Whiteflies are a problematic pest in gardens and greenhouses all over the world. These voracious insects breed rapidly, and it doesn’t take long for a full-blown infestation to take hold. Once established, they can be very difficult to get rid of!
The best way to defeat whitefly is to prevent them from moving in in the first place. Regular inspection of plants, cultivation of natural enemies and the use of yellow sticky traps and reflective mulches can all help to prevent an infestation from growing. If you already have a whitefly problem, putting together an integrated control plan is your best chance of getting rid of them. Combining preventative measures with insecticidal soaps, organic sprays and physical removal (such as vacuuming and water spraying) is the best way to eliminate an infestation.