How to Get Rid of Whitefly Naturally
How to Get Rid of Whitefly Naturally
- 1 How to Get Rid of Whitefly Naturally
- 2 Basil
- 3 Potassium soap
- 4 Garlic
- 5 Neem oil
- 6 Marigold
- 7 How to Control Whiteflies on Tomato Plants
- 8 How to Kill Whiteflies and Other Pests on Tomato Plants
- 9 How to Spot and Get Rid of Whiteflies on Your Garden Plants
- 10 What are Whiteflies?
- 11 The Whitefly Lifecycle
- 12 Signs of Whitefly Activity
- 13 How to Deal with an Infestation
- 14 How to Prevent Whiteflies
- 15 What Not to Do
- 16 The Bottom Line
- 17 Whitefly
- 18 Whiteflies in the Greenhouse
One of the most common plant pests to have at home is the whitefly, a small insect that digs into leaves and sucks the sap out of them. Countless crops and plants have been attacked by whiteflies, so prevention is essential for keeping them out of your orchard or garden. In this OneHowTo article we explain some how to get rid of whitefly naturally, so you know how to fight an infestation.
These herbs are capable of repelling whiteflies, so they are an ideal way of preventing whitefly, driving them away and stopping them from infecting our gardens.
You’ll need to plant basil on your balcony, garden or orchard as a home remedy to keep these insects away from other plants. You can also read this article on how to grow basil at home.
Another natural product that can be used to get rid of whitefly naturally is potassium soap, which is a totally ecological treatment. Dilute the product, which can be found in garden stores or department stores, in water and spray it on the plants.
The effect of potash or potassium soap on whiteflies is that it softens their bodies and suffocates them, because they breathe through their skin. So they will not get to the plant sap or damage the flowers or fruit.
Garlic is among the home remedies to get rid of whiteflies. This is a food with lots of benefits for the human body and for the health of plants.
We recommend crushing the garlic cloves, mixing them with water and applying this to the plants. You will repel whiteflies and other common garden pests.
Neem oil or neem is extracted from the neem tree and is a potent natural insecticide that can be used against many pests such as whitefly. It can be added to the irrigation water or applied directly to the infected leaves.
It is important to read the instructions and directions that come with this product and follow the recommendations of the manufacturer and specialists in plant protection products.
Marigold is another efficient plant to add to your garden if you want to get rid of whiteflies naturally as this plant are natural repellents. Moreover they are particularly beautiful and will look great in your garden. The only thing you’ll need to do is to plant them near the plant that has whitefly, you’ll soon see how they disappear.
If you want to read similar articles to How to Get Rid of Whitefly Naturally, we recommend you visit our Gardening & plants category.
How to Control Whiteflies on Tomato Plants
How to Control Whiteflies on Tomato Plants
Tiny whiteflies can kill off tomato plants if they aren’t promptly identified and treated. These small yellow-bodied insects have white wings, which they hold flat to their bodies or slightly tented. They feed on the underside of tomato leaves, sucking out sap and weakening the plant. Affected leaves begin to yellow and die, the leaf margins usually curling inward as damage progresses. Extensive feeding can leave a tomato plant susceptible to sooty mold and viruses spread by the pests. Prompt control prevents severe damage, so the tomatoes can grow and ripen normally.
Inspect the underside of tomato leaves for whiteflies or their nymphs, which resemble small white pods, before purchasing transplants. Shake the plant gently to make adult flies take to the air; if whiteflies are present, do not bring the plants home.
Weed the tomato bed and neighboring areas weekly so dead plant material doesn’t collect. Old plant debris provides a breeding ground for whiteflies.
Cover the bed with a silver-colored plastic mulch, which repels the whiteflies, prior to planting tomato transplants, Silver mulch protects young tomato plants for four to six weeks or until the foliage becomes lush and blocks the mulch.
Spray infested tomato plants with insecticidal soap, concentrating the spray on the underside of the leaves where whiteflies congregate and breed. Repeat the application every three days until no more whiteflies are present. Spray in the evening to minimize contact with beneficial insects. Insecticidal soap only works while wet, so rinse the plants with clear water the day after application to remove any residue.
Set out yellow whitefly sticky traps around the base of plants to control the adult population and minimize breeding. Replace the traps when they lose their stickiness or if they become covered in flies.
Release lady bugs or lacewing larvae, purchased from a nursery or seed supplier, into the garden to feed on the whiteflies. Introduced predator insects may migrate before they destroy the entire pest population, so use the insects only in conjunction with other control methods.
Things You Will Need
Yellow whitefly traps
Some pesticides are available for whitefly control, but they also kill beneficial insects, such as ladybugs, that feed upon whiteflies.
How to Kill Whiteflies and Other Pests on Tomato Plants
Whiteflies can transmit viruses like tomato yellow leaf curl between tomato plants.
Hemera Technologies/Photos.com/Getty Images
Various species of whiteflies will feed on tomato plants, including the greenhouse whitefly (Trialeurodes vaporariorum) and the silverleaf whitefly (Bemisia argentifolii). So will other pests such as aphids, mites and numerous bugs and worm-like or caterpillar larvae. These often will cause severe damage if you don’t deal with them. Whitefly feeding causes tomato leaves to turn yellow and curl, and can force uneven fruit ripening. Whiteflies also excrete honeydew, a sticky, sweet substance that attracts ants and fosters the development of sooty mold. To preserve your tomatoes, it is crucial that you practice excellent cultural care and encourage beneficial insects that prey on whiteflies and other tomato parasites.
Rotate or space out tomato plants and other potential whitefly hosts to minimize spread between crops, especially in areas where whiteflies have been a problem in previous growing seasons. Other silverleaf whitefly hosts include melons and cole crops.
Spread a reflective silver-colored aluminum mulch around the tomatoes just before or at the time of transplanting. This reflective mulch repels whiteflies, delaying whitefly buildup for several weeks when the young plants are particularly vulnerable. Reflective mulch is most necessary where whiteflies have previously spread viruses.
Spray infested tomato plants occasionally with a strong stream of water. A stream of water can directly disrupt feeding by knocking whiteflies, aphids, mites and other pests off the plant. It also washes honeydew and unsightly sooty mold off of the tomatoes, temporarily disrupts ants and allows beneficial predators and parasites to achieve better control of the tomato pests.
Spray infested tomato plants thoroughly with insecticidal soap, neem oil, pyrethrin or horticultural oil, making sure you completely cover both leaf surfaces and protected areas on the stem.
Remove and destroy or otherwise discard spent tomato plants, other crop residue and nearby weeds throughout and at the end of the growing season to avoid harboring whiteflies, other pests and diseases. Maintain weed-free areas around the edge of the garden and other nearby areas in the landscape.
How to Spot and Get Rid of Whiteflies on Your Garden Plants
Steph is a certified Square Food Gardening Instructor who has been gardening for more than 10 years in Canada where the winters are long and cold, and the summers are unpredictable. She is a volunteer for her community’s Incredible Edible project. In the past she created an educational gardening space for seniors and taught classes at a local community center where she created her own curriculum and activities. She participated in several local municipal garden days where she set up a booth to educate citizens about the joy of gardening.
These weak, pitiful flying insects don’t seem like a very formidable enemy, but whiteflies have the potential to kill entire crops in a short amount of time. By sucking the sap from healthy plants, they quickly turn a strong, productive plant into one that’s weak and dying.
Confession time: I’m a gardener with an insect phobia. Over the years, digging in the dirt and dealing with garden plants, I’ve become a bit more desensitized to insects. I’ve even come to love certain predatory and beneficial insects like ladybugs.
However, insect invaders like whiteflies still creep me out. They’re a big pain in the butt and can ruin your garden in no time flat. Don’t like em’ either? Here’s how to deal.
What are Whiteflies?
The name provides an excellent description of these tiny flying bugs. They’re white (usually), winged insects that look quite similar to aphids. They’re extremely common and are able to hide easily among plants because of their minuscule size.
They rarely grow to be more than a few tenths of an inch long and are skilled at hiding among garden debris.
There are a few different whitefly species, including the silver leaf whitefly. Other species vary slightly in color, size, and shape, some with a more yellowish hue.
Whiteflies feed on plants by sucking juices from the foliage. In heavily infested plants, this process inhibits photosynthesis.
By feeding off of plant foliage, whiteflies can also introduce diseases to your garden. They can spread fungal infections and viral diseases that can cause severe damage to your garden plants.
The Whitefly Lifecycle
Whiteflies overwinter (if it’s warm enough—they don’t tolerate freezing conditions) and are active in the summertime. They reproduce multiple times throughout the warm months.
Whiteflies lay eggs on the underside of leaves. Newly hatched larvae are incredibly tiny and tough to spot, but they’re just as hungry as adult whiteflies.
Whiteflies can severely damage a plant even in their larval stage because of the sheer number of active pests. One female can lay up to 400 eggs!
Signs of Whitefly Activity
Because whiteflies are active during the day, spotting them isn’t that difficult, despite their small size.
They don’t only infest outdoor garden areas, they’re common greenhouse and houseplant pests, too. They’re attracted to many sun-loving plants, including heat-loving flowers, tomatoes, eggplants, sweet potatoes, and peppers.
If you think you might have a whitefly infestation on your hands there are a few signs to look out for including:
- A sticky residue left on plant foliage (also known as honeydew). Ants are often attracted to this sticky, sweet substance.
- Stunted, yellowing plants with a sickly appearance
Whiteflies tend to congregate on the underside of leaves, which keeps them hidden, in most cases, from view. Check underneath plant leaves for the presence of white insects and their eggs.
How to Deal with an Infestation
You’ve spotted these tiny bugs and their eggs on your plants. YUCK! How should you attack the problem?
First, it’s important to be a diligent gardener. Spotting the problem early is vital. Inspect your plants frequently for signs of whitefly activity.
The easiest way to get rid of whiteflies is to physically dislodge them from foliage using a strong stream of water from your hose or with a handheld vacuum. This strategy works with multiple pests, including aphids.
You’re not done yet, though. Once you’ve gotten rid of the bugs with the hose, use a natural pest spray to cover the previously infested foliage.
Sprays containing dish soap help to deter whiteflies, though it’s not always an effective solution. A heavy infestation may not respond to these measures, and whiteflies may not be discouraged for long.
Neem oil is another option for getting rid of whiteflies. The substance suffocates the pests and kills them.
When applying any type of spray or topical oil treatment, do so in the morning or evening to prevent leaf burn and plant damage.
If there’s a heavy infestation, it’s best to remove affected plant matter as control of the bugs is unlikely to be successful.
As with many pests, preventative measures are much more effective and require a lot less effort in the long run.
How to Prevent Whiteflies
Prevention is the best medicine! Taking steps to cultivate a healthy garden ecosystem goes a long way towards protecting your precious plants.
Encourage the presence of predator insects that eagerly feed on tiny, vulnerable pests like whiteflies. Ladybugs, dragonflies, and spiders are known predators to these annoying bugs.
Use specialty mulches with a reflective quality to confuse whiteflies in search of host plants. The mulch deters the bugs but also help provide a warm environment for heat-loving plants like tomatoes and peppers.
Use sticky traps to capture flying insects like whiteflies. The traps won’t put a dent in a heavy infestation, but they’ll let you know when it’s time to pay attention and start dealing with a problem head-on.
If you’re purchasing plants from a nursery, always check the undersides of leaves to check for whitefly activity. I made the mistake of not doing so last year when I bought a few plants at my local garden shop, and I ended up introducing whiteflies to my garden.
They quickly infested other nearby plants that I have started indoors. It was a frustrating experience but a worthy lesson. It’s advice I definitely knew, but I stupidly forgot in the moment.
What Not to Do
I get it. Pest infestations are extraordinarily annoying and disheartening. But don’t grab the store-bought chemical pesticides in an effort to banish the problem. Doing so isn’t likely to do much good, and you’ll probably end up killing friendly insects in the process.
Row covers and other physical barriers aren’t of much use to prevent whiteflies from setting up shop in your garden because the bugs are so tiny. Plastic covers might help, but they’re not useful in the summer when conditions are already hot enough.
The Bottom Line
No one wants to deal with a whitefly infestation, but now that you have the tools to deal with it, you don’t have to let these little pests take over your garden. Let us know what methods work best for you in the comments below!
There are 2 main species present in New Zealand, Greenhouse Whitefly (Trialeurodes vaporariorum) and Citrus Whitefly (Orchamoplatus citri).
Whiteflies are small white sap sucking insects 1-2mm in length that resemble miniature moths with a wingspan of around 3mm. Both the nymphs and the adult insects are sapsuckers. Their feeding can harm the vigour of the plant, and help spread disease. As they feed they excrete a sugary substance (honeydew) and if left can allow sooty mould to grow on the leaves.
During warmer periods they can breed prolifically. The female whiteflies lay their eggs on the underside of a plants upper leaves. After 4-12 days the eggs hatch into crawling, sap-sicking nymphs.
Nicotiana (an attractive flower) is believed to attract whitefly and can be grown as a sacrificial plant or to serve as an early warning of their presence.
Various beneficial predatory insects will prey on whitefly and can help control numbers. To help attract beneficial predator insects grow a wide array of flowering plants including: alyssum, borage, hyssop, lavender, will help attract them. For more ideas click here
Spray with Mavrik. Repeat spraying twice in one week. Follow up spraying may be required in some circumstances.
Where possible, spray in the evening to avoid affecting beneficial insects.
Spray affected plants with Bugtrol, a highly effective organic insecticide. Spray the plant thoroughly, drenching the tops and bottoms all the leaves, twice in one week. If you spray this effectively dealing with whitefly should be easier as the eggs are smothered by the oil contained in this spray.
Follow up spraying may be required in some circumstances.
Where possible, spray in the evening to avoid affecting beneficial insects.
Whiteflies in the Greenhouse
E NTFACT-456: Whiteflies in the Greenhouse | Download PDF
by Jen White, Extension Entomologist
University of Kentucky College of Agriculture
Whiteflies are “true bugs” (Hemiptera) that feed on plant sap, much like aphids. Adults are very small (1/16 — 1/10 inch) with powdery white wings. Females lay eggs directly on the undersides of plant leaves. The eggs hatch into tiny “crawlers” that walk a short distance before settling at a feeding location. These nymphs lose their ability walk, and remain in the same location for the rest of their development until they pupate and emerge as winged adults (Figure 1). The entire whitefly life cycle takes about 3 weeks under favorable conditions, allowing populations to build quickly. Whiteflies do not have a dormant stage that can withstand freezing temperatures. In climates that have winter freezes, such as Kentucky, whiteflies are year-round pests only in greenhouses.
Figure 1. Lifecycle of the sweetpotato whitefly, entirely on the undersides of leaves. Development times in the figure are for 77°F on a preferred host plant species. Each stage will be longer at colder temperatures, or on a less preferred crop. Adults, eggs, and young nymphs are usually found on fresh newly expanded leaves, whereas older nymphs and exuviae are found on more mature foliage.
Worldwide, there are over 1500 species of whitefly, most of which are inconspicuous and never reach densities high enough to cause damage to their host plants. A few species, however, are major pests. Here in Kentucky, the most notable are 1) the sweetpotato whitefly (Bemisia tabaci), and 2) the greenhouse whitefly (Trialeurodes vaporarorium). The former is a confusing complex of “biotypes” (currently considered multiple species) that are physically indistinguishable, but which have distinct biological differences. For example, B biotype is also sometimes known as the silverleaf whitefly (also known as Bemisia argentifolii) because of the distinctive silvering damage it inflicts on plant leaves. B biotype is currently the most common in North America, but a second biotype, Q biotype, is also present, and of particular concern because Q biotype is highly resistant to many classes of insecticide. Finally, a third species, the bandedwinged whitefly (Trialeurodes abutiloneus) is an occasional pest of greenhouses. Other whitefly species are possible in the greenhouse (particularly on specialty crops such as citrus), but most of the time the culprit is one of these 3 species.
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.
Even worse, whiteflies are vectors that transmit over a hundred different plant viruses. The viruses are taken up by whiteflies feeding on an infected plant. When the whitefly moves to a new plant and starts feeding, viral particles enter the plant and start a new infection cycle. Plant species differ widely in both their susceptibility to these viruses and the symptoms they show. At the extremes, some plants species show no symptoms of infection (carriers) and other plant species become completely unmarketable. Of the greenhouse pest species of whitefly, sweetpotato whitefly is responsible for transmission of most viruses, but all three whiteflies can transmit viruses that can be damaging to crops. In general, whitefly vectored viruses are more frequently associated with vegetable than ornamental crops in the greenhouse.
Identification of Different Whitefly Species
Because different pest whitefly species differ in their susceptibility to control methods (see below) as well as the level of damage they can inflict, it is important to identify which species is infesting your greenhouse. You’ll need a handlens or magnifying glass to aid identification.
Figure 2. Species identification for common whiteflies in the greenhouse.
As adults, bandedwinged whiteflies are easily distinguished from sweetpotato and greenhouse whiteflies by the presence of a dark zig-zag pattern across the wings (Figure 2). Sweetpotato and greenhouse whiteflies are both solid white, but can be distinguished from one another as adults by the way they hold their wings. Greenhouse whitefly holds its wings out flat, giving it a triangular appearance from above, whereas sweetpotato whitefly holds its wings tentlike over its body at a sharp angle, giving the whitefly a more linear appearance from above, like a tiny grain of rice.
Fortunately, the immature “scale” of greenhouse and sweetpotato whitefly is easier to distinguish. Greenhouse whitefly nymphs are shaped like a pillbox, oval with flat perpendicular sides, and with noticeable long waxy filaments on the top. In contrast, nymphal sweetpotato whiteflies lack the perpendicular sides, lying more flat against the leaf. They also have only a few delicate filaments, which are quite hard to see. Bandedwinged nymphs look like greenhouse whitefly nymphs, but lack the long projecting filaments, instead having curly filaments on the top surface.
What Plants Might Be Attacked?
The list of plant species attacked by these pest whitefly species is unfortunately long. Table 1 includes some of the most important greenhouse crops attacked, but is far from complete. Sweetpotato whitefly is known to attack more than 700 species, and greenhouse whitefly is not much better. Bandedwinged whitefly has a more restricted host range, and while it may feed on many plants in the greenhouse, it won’t lay eggs on many crop species. Large numbers of adult bandedwinged whiteflies may enter greenhouses in the fall when vegetation in the landscape starts to die back, but will not necessarily become a persistent pest problem. That said, some greenhouse crops are known to sustain bandedwinged whitefly populations (Table 1). Additionally, bandedwinged whiteflies can reproduce on some species of weeds, such as beggarticks and ragweed, thus producing a continuous supply of adults to attack and weaken nearby crops.
Table 1: Some preferred greenhouse hostplants of whiteflies
BW= bandedwinged whitefly, GH = Greenhouse whitefly, SP = sweetpotato whitefly
*particularly prone to whitefly-vectored viruses
Integrated Pest Management
The old adage «an ounce of prevention is worth a pound of cure» (Benjamin Franklin) is certainly true when it comes to pest infestations of greenhouses. The following tips can help prevent infestations before they ever start:
Isolation/examination of new stock. Most whitefly outbreaks can be traced back to infested stock material. When new plants are brought in to the greenhouse, keep them isolated in a separate bay (best), bench, or area of the greenhouse. Because whitefly eggs and young nymphs are so small, it is very easy to miss early infestations. If new stock can be kept isolated for a period of 1-2 weeks, this allows time for larger nymphs to develop, which will be easier to detect. Use a hand lens or magnifying glass to check the undersides of young leaves before integrate new material with more established crops.
Screening. During warm dry seasons, whiteflies can become abundant in the environment, and may colonize greenhouses directly through open doors, windows and ventilation. Exclusion through screening may not always be feasible, but features such as double-door entry and covered ventilation could be considered in the construction of new greenhouses.
Sanitation. Remove plant residues from within and near the greenhouse. Whitefly nymphs can continue to mature on dead/dying plant material, producing adults that can reinfest crops. Some weed species are also favored hosts for whiteflies, so removing weeds from around (and within) the greenhouse makes it more difficult for whiteflies to cycle between greenhouse crops and the surrounding environment.
Crop free period. Because all stages of the whitefly life cycle are dependent on plants, allowing the greenhouse to stand empty of plants can also break the cycle of re-colonization and infestation. Adult whiteflies cannot live without feeding on a host plant (for more than a few days), so even a week at warm temperatures without plants should be sufficient to remove potential whitefly colonists from the greenhouse. In cooler temperatures, the plant-free period needs to be longer, so consider warming up the greenhouse for a few days prior to introducing a new crop, to purge and remnant populations. Once pest-free crops are established, avoid accidentally introducing «hitch-hiker» whiteflies as you move among greenhouses or bays. Avoid wearing colors that are attractive to whiteflies (yellow and blue), brush yourself off before entering clean areas, and try to avoid moving directly from infested to uninfested greenhouse areas.
As with most greenhouse pests, early detection of whitefly infestations is difficult due to the small size of the insect, as well as the preferred feeding location on the undersides of leaves. Yet, managing infestations is much easier when they are noticed early, so it is worth investing some time into monitoring efforts.
Yellow sticky cards are an essential tool for monitoring whitefly populations. These can be purchased in small quantities from most garden supply vendors. If you want to purchase in larger quantities, check out some of the vendors listed in Entfact 124, Vendors of microbial and botanical insecticides and insect monitoring devices.
Place the cards in a vertical orientation, so that the card is level with the new plant growth at the top of the crop. About 1-4 cards should be placed every 1000 ft2 of greenhouse, with extra cards placed near doors and vents where whiteflies might enter the greenhouse. In greenhouses with mixed crop species, higher card density should be used around crops that are particularly attractive to whiteflies.
Conduct regular scouting trips (weekly) through the greenhouse, inspecting both the yellow cards and plants. Look for unthrifty yellowing of plants, premature leaf drop, or sticky honeydew on the leaves. If you see these symptoms, use a handlens to inspect the plant more closely for insect infestations. Adult whiteflies will flutter away from plants if disturbed, so brushing your hand through the plant canopy in areas of concern may allow you to find hotspots of whitefly infestation.
Remember that finding a single whitefly on a yellow sticky card does not mean you should immediately apply a chemical control. Unnecessary chemical use is bad for the environment, human health, and the pocketbook. However, whitefly populations are easier to control when small, so don’t ignore early warning signs, either. Intensify monitoring efforts, and develop a plan of action for treatment. General “action threshold” pest densities such as 0.5 whiteflies/sticky card/day for young crops, or 2 whiteflies/sticky card/day for mature crops represent a starting point. However, the precise threshold at which action should be taken depends on many factors. Some crops are more forgiving of light levels of infestation than others, and some control methods take longer to take effect than others. In particular, if you plan to use biological control, it is better to act very early, perhaps even preventatively. Whatever action thresholds and control methods you use, keep records from year to year, so that you have more information about what worked (and what didn’t), to improve your future decisions.
Biological control. Biological control is often successfully used to suppress whitefly populations in greenhouses in Europe, but is less widespread in the United States. Currently, the following biological control agents for whitefly are available in the US:
Encarsia formosa is a parasitoid that lays its eggs in whitefly nymphs. It is even smaller than the whiteflies it attacks. The parasitoid larva develops within whitefly nymph, consuming it from the inside over a period of 1-2 weeks. This parasitoid will attack all 3 of the pest whiteflies discussed in this bulletin, but provides the best control against greenhouse whitefly, especially at cooler temperatures. Most commercially-available strains of this parasitoid do not provide good control of sweetpotato whitefly.
Eretmocerus eremicus is another parasitoid that is commercially available. It is generally considered to provide better control of sweetpotato whitefly than Encarsia inaron, and to perform better at higher temperatures.
Delphastus catalinae is a tiny predatory beetle (1/15 inch) that consumes whitefly eggs and nymphs. It will attack all species of whitefly, but prefers sweetpotato whitefly. It avoids eating whitefly nymphs that have parasitoids developing within them, which means that it can be released together with a parasitoid without interfering with parasitism.
Biological control is generally more expensive than chemical control, and won’t result in complete elimination of the pest. However, if you have a history of whitefly infestations that do not respond well to chemical controls, biological control may be able to accomplish what chemicals cannot. Moreover, organic biological control can add value to your crop. If you are considering biological control, carefully discuss your situation with a distributor of biological control organisms, who should be willing to help you use their products as effectively as possible. Vendors of these biological control organisms are listed in Entfact 125.
Chemical control. There are a number of chemicals labeled for whitefly control in the greenhouse in Kentucky (Table 2). These chemicals vary widely in their mode of action, crops they can be used on, compatibility with biological control, and efficacy.
“Resistant” pest populations develop when they are repeatedly and heavily exposed to the same chemical, killing off all but the few rare individuals that differ genetically in such a way that the chemical doesn’t affect them. These survivors reproduce, and their offspring inherit their resistance to the chemical. There are no “magic bullet” pesticides that won’t cause resistance. The solution is rotation: switching among chemicals with different modes of action to kill off survivors of the previous chemical. The mode of action is indicated by the IRAC code in Table 2. Rotating among chemicals within the same IRAC group is not helpful, because survivors of one chemical will probably also survive a second chemical that works in the same way. Likewise, there is no benefit to tank mixing chemicals with the same mode of action. Be sure to carefully follow label “resistance management” restrictions for application frequency. These guidelines have been put in place to prevent widespread resistance to particular chemical groups, to preserve the usefulness of the chemical.
Table 2. Chemicals for control of whitefly in the greenhouse
aO = ornamental, V = vegetable
bOMRI = Organic Materials Review Institute
cBiologicals = predatory and parasitoid insects.
If integrating chemical controls with biological controls, carefully consider the compatibility to the two control methods. As you might expect, insecticides are not generally good for beneficial insects, but some are worse than others. For example, insect growth regulators (IRAC code 7) are much more compatible with biological control than pyrethroids (IRAC code 3). Also note that organic (OMRI-certified) pesticides are not necessarily compatible with biological control. Chemicals with less residual activity in the crop and greater selectivity for particular groups of pests are more likely to be successfully integrated into a biological control program.
The diversity of ornamental crops in greenhouses poses particular challenges for pesticide use. When starting use of a new pesticide, you should initially apply it to only a small number of your plants. Monitor these plants for a few days for signs of phytotoxicity before treating the rest of your crop.
Hoddle, M. Silverleaf whitefly, Bemisia argentifolii. http://biocontrol.ucr.edu/bemisia.html
Greer, L. 2000. Greenhouse IPM: sustainable whitefly control. https://attra.ncat.org/attra-pub/viewhtml.php?id=51
Sabaratnam, S. 2012. Emerging virus diseases of greenhouse vegetable crops.
White, J. A. and D. Johnson. 2012. Entfact 124: Vendors of microbial and botanical insecticides and insect monitoring devices. ENTFact-124.
White, J. A. and D. Johnson. 2010. Entfact 125: Vendors of beneficial organisms in North America. ENTFact-125.
Zalom, F. G., J. T. Trumble, C. F. Fouche, C. G. Summers. 2011. UC IPM Pest management guidelines: tomato. http://www.ipm.ucdavis.edu/PMG/r783301211.html
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!