As you walk through the garden admiring the bright flowers and bountiful vegetables, a white insect flies past the leaves of the plant.
Upon closer inspection, you will notice that the leaves are mottled or yellowed and the plant looks like it is shedding some leaves. That’s why you are here. You were concerned that these little flies might be affecting your plants, so you searched for “whiteflies” and found this article. Well, you’ve come to the right place. Warm welcome!
Whiteflies are notorious pests that prefer a wide variety of plants, including common vegetables and ornamentals. We have everything you need to know about these insects, from identification and how to get rid of whiteflies naturally. Here’s what we’ll cover:
Whiteflies are not real flies. Instead, they belong to the order Hemiptera, which are related to aphids and mealybugs and form the whitefly family. There are 1,500 known species worldwide.
Since adults tend to flutter in white clouds when disturbed, these are some of the more visible and recognizable pests out there.
Pests in the immature and adult stages are suckers, which pierce plant tissue with needle-like mouthparts and suck the plant’s food, including the sugary products of photosynthesis, from the phloem.
They feed and breed best on the underside of the leaves.
Feeding can cause mottled, discoloured and yellowed leaves, eventually leading to necrosis. This damage reduces the photosynthetic capacity of plants, weakening them and reducing yield.
Certain species can also carry viruses that cause various plant diseases.
Diseases carried by whiteflies include Bergomo virus, which affects several important crops worldwide, such as tomatoes, cassava, soybeans and cotton, as well as many other virus types. Leaf roll virus and mosaic virus are common.
When they feed, these beetles secrete honeydew, which forms unsightly soot mold and attracts ants. Ants can disrupt beneficial insects that try to prey on or parasitize whiteflies.
Whiteflies attack vegetables and ornamental plants and are a problem, especially in warm weather.
Low numbers are usually not harmful unless they carry disease, but populations can grow rapidly, and high populations are notoriously difficult to control.
Outbreaks are often associated with disruptions in natural biological control, whether due to ants or pesticides, warm weather or dusty conditions.
These insects can cause significant crop damage and it’s no joke! Adults themselves usually don’t do much harm unless they spread disease.
Instead, it’s the nymphs that do the most damage.
It is difficult to distinguish most species even with a handheld lens. Identifying species often requires careful observation of the final instar stage (often called pupae) or inspection of the pupal shells remaining after the adults hatch.
The small adults have a yellow body, one sixteenth of an inch long, with four white wings and a white waxy appearance. Sometimes species that are similar in appearance can be distinguished by the angle of their wings.
Nymphs may look like scales or mealybugs: flat, round to oval and waxy.
Eggs are white, oblong, and are laid on the underside of leaves. Usually, eggs are arranged in a semicircle.
Why? Females do not stop eating when they lie down, but rotate around the feeding station.
Common species found on garden plants have a wide host range, including weeds and crops.
Silverleaf whitefly (Bemisia argentifolii) is probably the most common, attacking more than 500 species of plants, including roses, petunias, poinsettias, squash, broccoli, cauliflower, carrots, and more.
Certain crops can cause specific symptoms, such as mild root formation in carrots and irregular ripening in tomatoes, for example.
It is well known that the greenhouse whitefly (Trialeurodes vaporariorum) is widely distributed and has a wide range of hosts, including herbaceous plants, including tomatoes, coleus and purple.
The two species have overlapping host ranges and sometimes infest the same crop at the same time. To tell them apart, use a 10X or 40X handheld lens to check the wing angle.
The wings of T. vaporariorum are flat relative to the leaf surface, while the wings of B. argentifolii are at a 45-degree angle to the leaf surface.
The sweet potato, tobacco or cotton species (B. tabaci) also has a wide host range and can cause serious damage to some crops, especially since it is the most widespread virus-carrying whitefly worldwide.
Other species include the banded whitefly (T. abutilonea), which prefers poinsettia, geraniums, and petunias, and the white citrus fly (Dialeurodes citri), which affects citrus trees and some ornamental plants such as gardenias and lilacs.
Biology and Life Cycle
Females lay their eggs in the characteristic semicircular shape described above under the leaves, usually choosing younger leaves to lay their eggs.
Each female can live a month and a half and lay more than 200 eggs. Mating is not necessary because unmated females can lay haploid eggs, all of which hatch into males.
After hatching, insects go through four nymph stages, called instars.
The first of these is called a crawler. It has six legs and will move for a few hours after hatching before settling down for food. It usually moves only a few millimeters from its breeding grounds.
The next two stages are immobile, this time for feeding.
The fourth instar is sometimes called the pupae, although whiteflies do not undergo complete metamorphosis.
At temperatures of 65 to 75 degrees Fahrenheit, these pests take 10 to 12 days to transition from the creeping stage to the pupal stage.
The entire life cycle can last as short as two and a half to three weeks in warm periods and up to six months in winter.
Generations often overlap in populations, and you can find a representative of each stage on one plant!
>>> See more: how to get rid of scale insects
How to get rid of Whiteflies
Unfortunately, you cannot rely on the development of symptoms to know what is sucking your plants. Affected leaves may show no signs of damage until they turn yellow and fall off the plant.
Adults are not difficult to spot, however, as they fly through clouds when disturbed.
Commercial breeders use yellow sticky cards to monitor adult population size. While this is useful, it is not always accurate. Pops can hide next to a sticky map if their plants aren’t disturbed, giving you a false sense of ease.
Eggs and nymphs are difficult to see and require careful inspection of the underside of the leaves with a hand-held lens.
To keep track of the population, scan some plants in different areas of the garden for eggs, nymphs, and adults.
Monitoring is critical as control is difficult to achieve once a population is established.
Organic Control Methods
Adults are difficult to control because they fly away when disturbed, such as B. When you touch a plant or start applying a product. In addition, eggs and fourth instar (pupa) are immune to many pesticides.
On top of that, whiteflies are gifted at developing resistance to pesticides. Therefore, preventive techniques and the use of a wide range of strategies and the bounty of nature on natural enemies are the keys to achieving and maintaining control.
Integrated pest management (IPM) methods combine prevention, removal, and cultivation methods to safely and effectively control many insects. Learn more about IPM and how to design your own program.
Cultural and Physical Control
Thoroughly inspect all new plants for eggs and nymphs before introducing them into your garden.
While monitoring, remove and destroy leaves with eggs on them. Also, if possible, remove and destroy any severely infected plants.
Wash the plants with a strong stream of water, which helps remove pests and eggs during the feeding stage.
Ant control protects whiteflies from predators by applying a sticky substance such as Tangle Trap from Arbico Organics to trees and shrubs near the base of your plants. This will catch them trying to climb upstairs to collect honeydew.
Weed control is important because most whitefly species have multiple weeds that they happily overwinter and use as alternative hosts.
For example, B. argentifolii has more than 30 potential weed hosts, including thistle, milkweed, and white clover. Controlling these plants in your garden can help reduce pest numbers.
Drought-stressed plants are more vulnerable to attack and damage, so keep your plants well-hydrated and healthy.
However, avoid over-fertilizing, especially nitrogen, which increases pest reproduction, improves survival chances and promotes faster development.
Lacewings, predatory insects such as small pirate bugs (Anthocoridae), big-eyed beetles (Geocoridae) and assassin bugs (Reduviidae), beetles such as Delphastus species and predatory mites all target whiteflies.
Attract these goodies into your garden by adding a variety of flowering plants like yarrow and dill.
It also provides some control over T. vaporariorum and T. abutilonea. Buy these from Arbico Organics and use them preventively.
There are several native predatory Delphastus beetles that control whiteflies, each favoring a specific type, including D. pusillus, D. pallidus, and D. catalinae. Adult D. catalinae is available from Arbico Organics.
Amblyseius swirskii, a predatory mite commonly used to control red spiders and thrips, also attacks these white-winged pests. Eat up to 20 eggs a day! Find these mites at Arbico Organics and use them preventively or apply them to infested plants.
Products containing Beauveria bassiana, a parasitic fungus, are used as bioinsecticides to control whiteflies as well as many other pests.
Try BioCeres WP or BotaniGard from Arbico Organics.
Intentional biological control is most effective when combined with predators or produce. For example, use E. formosa or E. eremicus with B. bassiana and Delphastus species or green lacewing release.
You can also help release biological control through pesticide application.
As described below, insect growth regulators (IGRs) may be compatible with beneficial insects because they affect only immature insects during molting.
For example, E. emericus alone may require up to three introductions to achieve control, but this can be expensive. Combine it with the IGR app and you only need one at a time for satisfying results and keeping costs to a minimum.
Because adults and pupae are insensitive to most pesticides, it may take four to five weeks of weekly use of organic and chemical pesticides to achieve control or successfully eliminate all stages.
Chemical Pesticide Control
Insect growth regulators (IGRs) can be used safely with many beneficial predators.
Thiazinone and pyriproxyfen are two examples of IGRs, which are considered low-risk chemicals, meaning they pose a low risk to both humans and wildlife. These products can penetrate leaves and attack bottom-eating pests.
Carbamates, organophosphates, and pyrethroids provide fast knockdowns in large populations, but since these options are not selective, they also kill beneficial ones.
Systemic pesticides delivered through plants are more effective than contact pesticides. But many of them, including neonicotinoids, can negatively affect beneficial insects.
Clouds of Trouble Brewing
The last thing you want to see popping out of your beautiful vegetable patch or flower bed is a clump of flying white insects. The damage they and their children have done is even worse.
Not only can they leave mottled, yellowed, or fallen leaves, but they can also transmit some serious viral diseases. Fortunately, you now know how to use all of nature’s goodies and various cultivation methods, as well as the occasional spray of organic pesticides in extreme cases, to control these crop threats.
Tell Answer The Question about your experience with whiteflies in the comments below, which of your plants they seem to prefer and your strategy!