About Katie Piercy
Katie Piercy has worked in the conservation industry for over a decade and has had a wide-ranging and varied career. She has spent time working in a number of different environments and with a range of different animals. Her roles in the UK have included rearing and releasing corncrake (Crex crex) chicks in the Nene Washes, a seasonally flooded area of wet meadows, chasing hen harriers (Circus cyaneus) in the Scottish Uplands and restoring areas of peatland in the West Midlands.
Whiteflies are small flying insects that feed on the sap of plants. They are not harmful to humans, but they are a major agricultural pest. In particular, the honeydew they produce can cause the spread of mould on the surface of the plant leaf.
Table of Contents
- What is a whitefly?
- What is the lifecycle of a whitefly?
- Are whiteflies harmful to pets?
- Whiteflies: An irritation, not a threat
- What do whiteflies do to humans?
- How do I get rid of white flies?
- Can whiteflies bite humans?
- How are whiteflies harmful?
- Are whiteflies good or bad?
- Do whiteflies make you itch?
- What causes whitefly infestation?
- Can vinegar get rid of whiteflies?
- How long do white flies last?
- Do white flies lay eggs in soil?
- What are whiteflies attracted to?
- Are Whiteflies Harmful to Humans? (or Pets?) – Meadowia
- Are Whiteflies Harmful to Humans? – GardenVersus.com
- Relationship between Some Environmental and Climatic …
- Are Whiteflies Harmful To Humans – How To Discuss
- Whiteflies: Eliminating Tiny White Pests – Epic Gardening
- Whiteflies, Irritating But Harmless – Financial Tribune
- Whiteflies – Catseye Pest Control
- Whiteflies Management Guidelines – UC IPM
What is a whitefly?
Somewhat confusingly, whiteflies are not actually flies, and they sometimes aren’t even white. Whiteflies are a type of insect that sit within the true bug family, like aphids and scale insects. Like their relatives, they feed on the sap of plants by poking their mouthparts into the xylem and drinking the fluids within.
As adults, whiteflies are relatively small, largely less than 2mm (0.08in) in length, and have two pairs of waxy wings positioned over their bodies in a triangular form. There are around 1,500 whitefly species globally. Some have patterned wings, and a few can even be black in colour, but the most well-known species are white, giving the group its name.
What is the lifecycle of a whitefly?
Whiteflies start life as an egg. The female lays these eggs on the underside of a leaf. The eggs are a yellowy-white colour and pointed at both ends. If the female has not been mated with when she lays these eggs, then they will all hatch to be male whiteflies. The females will then mate with her offspring to produce female eggs. A single female can lay around 400 eggs and will lay them in circular patterns.
As they mature, the eggs will slowly take on a darker colour, and they will hatch to produce a nymph, known as a crawler. The juvenile whiteflies are mainly flat and oval in shape. This nymph will go through four instars as it slowly develops towards being an adult, but it only has functioning legs in this first stage. The crawlers will make their way across the leaf before attaching their mouthparts to the leaf surface and beginning to feed.
As they then moult into the successive instars, they will remain attached to the plant by their mouth. In the final stage, the nymph develops into a pupa in order to transform into an adult. This pupa is oval and spikey. Once the whitefly has transformed it will burst out of the pupal case and pump up its wings to unfurl and dry them.
It can then start the whole cycle again. An adult will live for several months, feeding on sap as the nymphs have done.
Whiteflies do not bite humans, as their mouthparts are designed to pierce plant matter rather than flesh. Mostly they will fly away if disturbed, and they are too small to be of interest to humans in a culinary manner. The main impact whiteflies have on humans is the damage they cause to agricultural crops and other decorative plants.
As both the adult and the nymphs feed on sap, they can weaken plants through this feeding process and the damage they do as they cut into the plant. However, in general, it’s less the action of feeding that affects plants but the fact that this process encourages the establishment of damaging moulds and causes the transmission of disease.
When the whitefly starts feeding, it secretes spit into the cut; this can introduce bacteria and moulds picked up from other plants. More harmful, however, is the excretion of honeydew by the adults and larvae, which they produce as a waste product from sap they consume. This sugary substance coats the leaves of the plant they are feeding on and causes the growth of mildews and other moulds. Many species, such as ants, actually feed on the honeydew as a source of sugars and nutrients.
Whiteflies are difficult to control and are even small enough to fit through mesh erected in greenhouses to keep out pests. Therefore, while they aren’t technically harmful to humans, they are an irritating pest to gardeners and farmers and can affect the production of our crops, which can impact the availability of food.
Are whiteflies harmful to pets?
Because they do not bite, whiteflies are not harmful to pets. Many pets may find small flying insects either alarming or intriguing, meaning they may hide away from them or try to investigate them, but these tiny flies are really just getting on with their day.
Because whiteflies are so hard to get rid of, many people turn to pesticides to control them. However, some pesticides can be harmful to pets. So while the whiteflies themselves are not harmful, the things we do to prevent them may be.
Whiteflies: An irritation, not a threat
Whiteflies are an incredibly irritating pest that causes a great deal of damage to commercial plants. However, they are also a great source of food for many animals, from ladybirds to damselflies, even to some bird species. While we may never be grateful to see them on our favourite plants or in our crop fields, at least they are not directly harmful to humans, meaning one less annoying biting insect when we’re out and about on an evening stroll.
What do whiteflies do to humans?
They are not harmful to humans, but they are a major agricultural pest. In particular, the honeydew they produce can cause the spread of mould on the surface of the plant leaf.
How do I get rid of white flies?
A simple solution made from liquid dish soap and water will kill adult whiteflies without harming plants. Add 1 tablespoon of liquid dish soap to 1 gallon of water and mix well. Pour the solution into a plastic spray bottle and spray it on all infested plants, saturating the leaves’ upper and undersides and the stems
Can whiteflies bite humans?
Whiteflies are not known to bite humans, but they do have piercing mouthparts they use to extract fluids from plants. They are very similar to a mosquito.
How are whiteflies harmful?
Whiteflies can seriously injure plants by sucking juices from them, causing leaves to yellow, shrivel, and drop prematurely. If the numbers of whiteflies per leaf are great enough, it could possibly lead to plant death. The second, which is known as ?indirect? damage, is caused by the whitefly adults.
Are whiteflies good or bad?
Whiteflies are tiny winged insects that suck the sap of the plants. If you have a bad infestation, leaves of the plant turn yellow, wilt and eventually dry out and fall off the plant. Whiteflies are a common greenhouse pest, but at certain times of year, they can be a problem on landscape or vegetable plants.
Do whiteflies make you itch?
The abundance of whiteflies in Tehran can cause health problems including itching, red and sore eyes, runny nose, allergies, and problems in the respiratory system of individuals, especially asthmatics (29).
What causes whitefly infestation?
As much as your plants like nitrogen-rich fertilizers, whiteflies like your nitrogen-rich plants, as well. Excessive nitrogen fertilization can cause frequent infestations. While nitrogen can boost the vitality of your plants, over-fertilizing your garden can attract whiteflies, leading to more frequent infestations.
Can vinegar get rid of whiteflies?
Try making your own insecticidal soap with a recipe of one gallon water, 2 t baking soda, 2 t dish detergent, and 2 t white vinegar. Spray the pest treatment under the leaves of your plants where the white fly eggs, scale and adults reside.
How long do white flies last?
The entire lifecycle of the whitefly lasts only about 22 days, but an infested plant often shows all phases of the insect present at the same time. So, unless treated, the infestation is likely to be permanent, with new eggs hatching constantly into new larvae that will produce new adults to lay more eggs.
Do white flies lay eggs in soil?
Whiteflies can kill otherwise healthy plants. They dwell primarily on plant leaves, but the eggs can also infect the soil. Once the eggs hatch, the larvae feed on plant material sitting on the soil’s surface until they grow wings and move into the foliage of the plant.
What are whiteflies attracted to?
Whiteflies are highly attracted to yellow objects, a behavior that is exploited in gardens and greenhouses by the use of yellow sticky traps. These sticky cards, stakes or tapes catch only the flying adults and are more appropriately used as a monitoring device.
Are Whiteflies Harmful to Humans? (or Pets?) – Meadowia
Are Whiteflies Harmful to Humans? (or Pets?)About Katie PiercyKatie Piercy has worked in the conservation industry for over a decade and has had a wide-ranging and varied career. She has spent time working in a number of different environments and with a range of different animals. Her roles in the UK have included rearing and releasing corncrake (Crex crex) chicks in the Nene Washes, a seasonally flooded area of wet meadows, chasing hen harriers (Circus cyaneus) in the Scottish Uplands and restoring areas of peatland in the West Midlands. Whiteflies are small flying insects that feed on the sap of plants. They are not harmful to humans, but they are a major agricultural pest. In particular, the honeydew they produce can cause the spread of mould on the surface of the plant leaf. What is a whitefly? Somewhat confusingly, whiteflies are not actually flies, and they sometimes aren’t even white. Whiteflies are a type of insect that sit within the true bug family, like aphids and scale insects. Like their relatives, they feed on the sap of plants by poking their mouthparts into the xylem and drinking the fluids within. As adults, whiteflies are relatively small, largely less than 2mm (0.08in) in length, and have two pairs of waxy wings positioned over their bodies in a triangular form. There are around 1,500 whitefly species globally. Some have patterned wings, and a few can even be black in colour, but the most well-known species are white, giving the group its name. What is the lifecycle of a whitefly? Whiteflies start life as an egg. The female lays these eggs on the underside of a leaf. The eggs are a yellowy-white colour and pointed at both ends. If the female has not been mated with when she lays these eggs, then they will all hatch to be male whiteflies. The females will then mate with her offspring to produce female eggs. A single female can lay around 400 eggs and will lay them in circular patterns. As they mature, the eggs will slowly take on a darker colour, and they will hatch to produce a nymph, known as a crawler. The juvenile whiteflies are mainly flat and oval in shape. This nymph will go through four instars as it slowly develops towards being an adult, but it only has functioning legs in this first stage. The crawlers will make their way across the leaf before attaching their mouthparts to the leaf surface and beginning to feed. As they then moult into the successive instars, they will remain attached to the plant by their mouth. In the final stage, the nymph develops into a pupa in order to transform into an adult. This pupa is oval and spikey. Once the whitefly has transformed it will burst out of the pupal case and pump up its wings to unfurl and dry them. It can then start the whole cycle again. An adult will live for several months, feeding on sap as the nymphs have done. Also read: How to Deal with Whiteflies on Plants? (Prevent Damage) Whiteflies do not bite humans, as their mouthparts are designed to pierce plant matter rather than flesh. Mostly they will fly away if disturbed, and they are too small to be of interest to humans in a culinary manner. The main impact…
Are Whiteflies Harmful to Humans? – GardenVersus.com
Are Whiteflies Harmful to Humans?Usually, the white flies are not harmful to humans but it causes damage to crops and fruits. The white fly is a major agricultural pest that affects plant growth and yields. Whiteflies feed on the sap of plants and cause mold growth on the leaf’s surface. This article will tell you about are whiteflies harmful to humans.“The answer is ‘no’.” Are you one of those people who just love to go outside and catch whiteflies? You might not think so, but these tiny flying insects can cause a lot of damage to crops. For example, they can wreak havoc on greenhouse crops like tomatoes and peppers, as well as many fruits and vegetables. Whiteflies can even attack trees, leaving branches weak and vulnerable. Keep reading the article to know about are whiteflies harmful to humans. What is whitefly? whitefly is a pest that attacks certain plants. Most people have heard of aphids, but whitefly looks similar. Like whitefly, these pests are very tiny and can infest plants. They can leave behind a honeydew, which attracts ants, which then feed on the plant’s lees.Whiteflies are sap-sucking pests that can be found on fruit and vegetable crops. They suck the juices out of plants and often cause the leaves to wilt and turn brown. Whiteflies are also a major concern in commercial horticulture. The insects attack many types of crops, but their preferred plant hosts include cucurbits, legumes, grapes, and trees.What is the life cycle of the whitefly?The lifecycle of the whitefly begins when it first emerges from the egg case. It’s then about three weeks old and crawls its way across the plant to the first leaf. Next, it climbs up the stem of the plant, until it reaches the top of the plant, where it’s about a week old. A whitefly’s life expectancy is about one week on the plant, during which time it sucks the sap from the leaves, and then falls off the plant and dies. That’s why it’s so important to prevent whiteflies from spreading on plants.Are Whiteflies harmful to humans?Whiteflies are not harmful to humans but they can transmit disease to plants. Infected plants are not suitable for the consumption of humans. It reported that an abundance of whiteflies in Tehran has caused serious health problems like red eyes, allergies, and runny noses.The whitefly is a small, pale-colored insect that sucks the juice out of plants, and it’s no fun for anyone who cares about their backyard garden. But despite the obvious dangers of this pest, whiteflies are not harmful to humans. While they can transmit diseases to humans, there have never been any documented cases of a whitefly-transmitted disease in humans. The only species of whitefly that is known to spread viruses in the human population are the plant louse, which is a tiny version of mosquitoes.Are whiteflies harmful to pets?Whiteflies are often seen in the garden as annoying pests. However, these small, winged insects can pose a real threat to our pets. While the insects may seem harmless, they can cause allergic reactions, including dermatitis and hives. Are whiteflies disease carriers?While the whitefly’s role as a vector is well-known, a more recent discovery suggests that these insects may be a carrier of human disease. A team of researchers collected whiteflies in two rural areas of Texas and tested them for the presence of bacteria that cause Lyme disease,…
Relationship between Some Environmental and Climatic …
Relationship between Some Environmental and Climatic Factors on Outbreak of Whiteflies, the Human Annoying Insects Journal List J Arthropod Borne Dis v.14(1); 2020 Mar PMC7382691 J Arthropod Borne Dis. 2020 Mar; 14(1): 78–87. AbstractBackground:The reports of numerous outbreaks of whiteflies from different parts of the world have increased its medical importance. The aim of this study was to determine relationship between environmental changes and climatic factors with the outbreak of the whitefly population in Tehran, the capital of Iran.Methods:This study was carried out in urban areas of Tehran, where the increasing population of whiteflies was reported frequently during 2018. In order to entrap the whiteflies, 20 yellow sticky cards smeared with white refined grease were installed on the trunks of the trees at twice per month as trapping time intervals. The captured flies were transferred and conserved in cans containing 70% alcohol and were counted accurately under a stereomicroscope. To determine the relationship between air quality index, precipitation, air temperature and air humidity as environmental and climatic factors with the abundance of whiteflies, change point analysis and Generalized Estimating Equations (GEE) was used.Results:The most density of white flies per trap was 256.6 and 155.6 in early October and late September respectively. The number moved closer to zero from November to April. The population of whiteflies was inversely correlated with the level of air quality index (p= 0.99) and precipitation (p= 0.95), and it had a direct correlation with the high temperature. Also, the population of whiteflies had a direct correlation with the level of air humidity in the first half of the yearConclusion:According to these findings, during spring and summer from early May to early October.Keywords: Change point analysis, Climatic factors, Environmental change, Outbreak, TehranIntroductionWhiteflies (Hemiptera: Aleyrodidae) feed on a wide range of hosts in a way that for some species more than 900 plant species have been identified (1, 2). Cucurbits and ornamental plants, agricultural crops, palms, and weeds are the main hosts of this pest, though there are many weeds which are the secondary hosts (3). The life cycle of whiteflies from egg to adult complete one month depending upon environmental temperature. Adult whiteflies may be surviving for one to two months (4). This insect is considered a health problem and an important medical pest that can also threaten human safety in some cases. Accidental entry of a whitefly into the human respiratory tract can cause inflammation and infection in the upper respiratory tract leading to the emergence of opportunistic fungal and bacterial infections (5). The population of this insect has increased in many parts of the world which has caused many problems for humans, especially in urban areas (6). According to experts, repeated and uncontrolled use of various formulations and concentrations of pesticides can have many adverse effects, such as the resistance of pests to pesticides, the emergence of new pests, and the eradication of natural enemies (parasitoids and predators). Whiteflies are among the pests that have been evolved by continuous use of chemicals and the lack of proper management of pesticides (7). In addition to direct physical and biological harm for human, these insects cause a sharp decline in the production of agricultural products….
Are Whiteflies Harmful To Humans – How To Discuss
Are Whiteflies Harmful To Humans
Whiteflies: Eliminating Tiny White Pests – Epic Gardening
Whiteflies: Eliminating Tiny White Pests Much like aphids, whiteflies are a scourge in the garden. These tiny pale pests fly around sucking plant juices and spreading diseases. Worse yet, they’re so minuscule that they can fit through a lot of mesh screening. Because of this, the whitefly is also a major problem in greenhouses and indoor growing spaces. But don’t panic, you can eliminate these white insects from your greenhouse or garden. Let’s talk about whiteflies, how they multiply, and how to get rid of them! Subscribe to the Epic Gardening Podcast on iTunes or Spotify Good Products At Amazon For Eliminating Whiteflies: Safer Brand Insect Killing SoapBonide All-Seasons Horticultural and Dormant Spray OilMonterey Take-Down Garden SprayYellow Sticky TrapsLadybugsNeem Bliss 100% Cold Pressed Neem OilTanglefoot Tangle-Trap Whiteflies Overview Common Name(s)Whiteflies, citrus whitefly, ash whitefly, greenhouse whitefly, giant whitefly, bandedwinged whitefly, silverleaf whitefly, and many other related namesScientific Name(s)Multiple, all in the Aleyrodidae family of insectsFamilyAleyrodidaeOriginWorldwidePlants AffectedMost agricultural crops (especially brassicas, tomatoes, capsicum and citrus), some ornamentals, some medicinal crops. The silverleaf whitefly feeds on poinsettia. Common RemediesRemoval of pests (with water or vacuum), garlic sprays, insecticidal soaps, horticultural oils, pyrethrin-based sprays, yellow sticky traps, whitefly predators (such as ladybugs, lacewings, whitefly parasite, hummingbirds, and dragonflies), neem oil, reflective mulches, and sticky ant traps around fruit trees Life Cycle Of Whiteflies In the latter part of spring, whitefly adults place their eggs on the undersides of leaves. Typically, these are done in concentric patterns, towards the upper portion of the plant. An adult whitefly can produce 200-400 eggs. Five to ten days later, the whitefly eggs will hatch into whitefly nymphs. In the first instar or larval phase, the nymphs are referred to as crawlers. They move a short distance away from their egg and then flatten against the leaf to feed. There are a total of four instars, but once the crawler has picked its location, it remains there throughout further instars. These nymphal stages can be hard to identify. Once they’ve stopped crawling and latched onto the leaf, they look very similar to scale insects. Often their coloration blends in with the leaf they’re on, or is slightly paler in hue. After the nymphal stages have concluded, the whitefly larva will pupate. Within a week, the whitefly emerges from its old skin as a new adult to begin its own egg-laying process. These tiny white flying bugs can live for a couple of months as adults before dying off. Common Habitats For Whiteflies Whiteflies live the majority of their lives on or near their host plants. While adults can fly and thus can find new susceptible plants to lay eggs on, the nymphs don’t leave their food source. Then eggs hatch and nymphs emerge. Nymphs overwinter on their host plants on the underside of leaves, where they’ve latched on to feed. However, they don’t tolerate extremely cold climates well and will die off if they are exposed to freezing conditions. This makes them a common greenhouse pest, as the climate inside a greenhouse is usually warm enough for them to survive. In fact, there is a particular species of whitefly, the greenhouse whitefly (Trialeurodes vaporariorum) which tends to live most of its lifespan on indoor plants! Adult whiteflies cannot survive for more than a few days without feeding on plant sap. If you’ve found tiny white bugs on plants, you may have found whiteflies. They may be eating, laying eggs, or sheltering from inclement weather. What Do Whiteflies Eat? Both adults and nymphs feed on plant sap. However, different species of whiteflies feed on different kinds of plants. For instance, the cabbage whitefly (Aleyrodes proletella) feeds on brassica species. There are whiteflies that feed on a wide range of…
Whiteflies, Irritating But Harmless – Financial Tribune
Whiteflies, Irritating But Harmless September 12, 2015 17:55 Residents of Tehran have had to deal with an unwelcome guest in the form of whiteflies for the past few years, particularly those who live or work in the Iranian capital’s central districts. Some have voiced concern over the bug’s effects on human health, a concern aggravated by the bug’s exotic and unusual white color. However, experts say there is little to worry about. “They damage plants, but besides irritating people they do little else in the way of harm to humans,” Ebrahim Azizkhani, an entomologist, told Borna News Agency. Azizkhani admitted that whiteflies may cause breathing difficulties when they enter the mouth or nostrils, “but it’s nothing serious worth panicking over.” Whiteflies are sap feeders that reduce the overall vigor of plants with their feeding. As whitefly infestations become severe, they cause plants to yellow and lose their leaves prematurely. They also produce large amounts of sticky, sugary honeydew, which in turn is colonized by black sooty mold, reducing the attractiveness and marketability of whitefly-infested crops. The expert attributes the rise in whiteflies numbers in Tehran to global warming. Some have suggested that the bugs may have piggybacked to Tehran on imported ornamental plants. Azizkhani said pesticides provide the best solution to the problem but warned that because whiteflies are found in densely-populated public spaces, studies must be done before pesticides are used on an extensive scale.
Whiteflies – Catseye Pest Control
Whiteflies | Catseye Pest Control Whitefly Facts Whiteflies are insects that can greatly impact agriculture and spread disease, affecting food production all around the world when they feed. While they will affect food, their presence will also have an effect on the larger economy, costing farmers and consumers a lot of money by driving up food prices. Whitefly Bites Whiteflies are not known to bite humans, but they do have piercing mouthparts they use to extract fluids from plants. They are very similar to a mosquito. Whitefly Life Cycle The whitefly is a species that thrives in warm environments and cannot survive the cold. Females will lay yellow eggs in semicircles on the undersides of plant leaves that turn a darker shade over the course of 24 hours. After 5 to 7 days, nymphs appear and will flatten themselves against the leaves to start feeding. They will spend another week as translucent pupae that look similar to mealy bugs before they develop into full grown adults. Most females will lay eggs in the late spring, and under the best conditions, they can lay up to 400 eggs over a two-month period, but usually much less. One generation of whiteflies will develop over three to four weeks. These flies love plants, both indoors and outside. They will feed on vegetables and flowers, effectively killing them. If they occur in large groups, this is especially dangerous to farmers because their crops will be threatened. They can also affect potted houseplants if they are found inside. Types of Whiteflies Ficus Whitefly Ficus whiteflies are between 1.4mm and 1.6mm with white wings and dark red eyes. Their wings have faded gray-brown markings. These pests lay their yellowish eggs on the underside of leaves along the vein in the middle. The early stages of this insect can be seen on both the top and bottom of leaves, which differs from other whitefly species. They primarily damage various species of Ficus plants and Rhododendron. Rugose Spiraling Whitefly Rugose spiraling whiteflies, at 2.5mm, are larger than other whitefly species in the United States and move more slowly. These pests have irregular faded brown bands on their wings and males have a pair of pincers at the end of their abdomens. They lay their eggs in a spiral on the underside of leaves, hence the name. The eggs are coated in a waxy, white material. Whitefly Infestations Whiteflies can’t handle cold weather, so they prefer warmer climates, greenhouses or inside your home. As long as it is warm out you’ll most likely find them underneath leaves out in your yard. Their nymphs attach to the plants and feed off them. They will do the same to your houseplants or any you bring in from outside when the temperatures drop. Whitefly infestations can spread quickly. Frequently Asked Questions How do you control a whitefly infestation? Most whiteflies infestations occur from plant materials that started off with eggs in the first place. You’ll want to give your new plants a look-over and separate the affected plants from the clear ones so they will not be disturbed by the flies. It may also help to trap whiteflies. They love yellow and white lights and will often be found buzzing around them, as well as lightly-colored foliage. To trap them, place colored sticky traps around affected areas such as infested plants. Biological control is also possible with the introduction of parasitic wasps. The Encarsia Formosa wasp develops within young whiteflies, turning them black and killing them. This is only possible in warmer environments that average 72 degrees. The parasitic wasp Eretmocerous californicus kill whiteflies through “blood feeding” when young whiteflies are stung by the wasps. Instead of laying eggs, the adult whitefly will feed on the blood from the wound of its young. What are the benefits of professional whitefly pest control? A pest management professional has the education, equipment and skills necessary to effectively address a whitefly problem. Finding and treating the whiteflies can be challenging, especially if they are hidden in the building. A pest management professional provides their expertise to identify the pest…
Whiteflies Management Guidelines – UC IPM
Whiteflies Management Guidelines–UC IPM UC IPM Home > Homes, Gardens, Landscapes, and Turf > Whiteflies How to Manage Pests Pests in Gardens and Landscapes Whiteflies Revised 9/15 In this Guideline: Adult greenhouse whiteflies on undersides of leaves. Sweetpotato whitefly adults and nymphs. Encarsia inaron parasite laying an egg in an ash whitefly nymph. A parasite has emerged from the round hole in the whitefly nymph at the bottom. Greenhouse whitefly nymphs turn black when they are parasitized. Whiteflies are tiny, sap-sucking insects that may become abundant in vegetable and ornamental plantings, especially during warm weather. They excrete sticky honeydew and cause yellowing or death of leaves. Outbreaks often occur when the natural biological control is disrupted. Management is difficult once populations are high. IDENTIFICATION AND LIFE CYCLE Despite their name, whiteflies are not true flies (in the insect order Diptera) but are in the order Hemiptera, related to aphids, scales and mealybugs. They derive their name from the mealy white wax covering the adult’s wings and body. Adults are tiny insects with yellowish bodies and four whitish wings. Although adults of some species have distinctive wing markings, many species are most readily distinguished in the last nymphal (immature) stage, which is wingless and lacks visible legs. Depending on species, whitefly nymphs vary in color from almost transparent yellow or whitish to black with a white fringe (Table 1). Whiteflies develop rapidly in warm weather, and populations can build up quickly in situations where natural enemies are ineffective and when weather and host plants favor outbreaks. Large colonies often develop on the undersides of leaves. The most common pest species—such as greenhouse whitefly (Trialeurodes vaporariorum) and sweetpotato whitefly (Bemisia tabaci)—have a wide host range that includes many weeds and crops. These species breed all year round in warmer parts of California, moving from one host to another as plants are harvested or dry up. Another species of whitefly with a broad host range is the giant whitefly, Aleurodicus dugesii, which invaded Southern California in the early 1990s. It is now found in coastal areas and interior valleys in much of the state on a number of tropical and semi-tropical ornamental species. For more information on this species, see Pest Notes: Giant Whitefly. Other species of whiteflies, especially those on woody species, often have a more limited host range. Table 1 lists common whiteflies in California gardens and landscapes. Whiteflies normally lay their tiny oblong eggs on the undersides of leaves. The eggs hatch, and the young whiteflies gradually increase in size through four nymphal stages called instars. The first nymphal stage (crawler) is barely visible even with a hand lens. The crawlers move around for several hours before settling to begin feeding. Later nymphal stages are immobile, oval, and flattened, with greatly reduced legs and antennae, like small scale insects. The winged adult emerges from the last nymphal stage (sometimes called a pupa, although whiteflies don’t have a true complete metamorphosis). All stages feed by sucking plant juices from leaves and excreting excess liquid as drops of honeydew as they feed. DAMAGE Whiteflies use their piercing, needlelike mouthparts to suck sap from phloem, the food-conducting tissues in plant stems and leaves. Large populations can cause leaves to turn yellow, appear dry, or fall off plants. Like aphids,…