The common name "whitefly" is applied to more than 1500 species in many genera from the Aleyrodidae family of insects that also includes aphids and mealybugs. Many different types of whiteflies can infest plants, depending on the region where you live and the type of plant being affected. These tiny, heart-shaped flies are generally no more than 1/10 inch long. If the infestation is serious, a cloud of whiteflies will suddenly go airborne like a burst of snow when a plant is bumped or moved. This phenomenon is one way to identify a whitefly infestation.
Whiteflies can be found indoors and outdoors, but they are a bigger problem in greenhouses and on indoor houseplants, since cold weather and natural predators tend to keep outdoor populations in check. These are piercing/sucking insects that can weaken a plant, though it's fairly rare for a plant to be actually killed. An indoor whitefly infestation can quickly spiral out of control, so it's best to treat whiteflies at the first signs.
Whitefly Plant Damage
These annoying insects aren't only a nasty surprise for plant owners, but problematic to the health of the plant, too. The nymphs and various larval stages attach to the plant's soft tissues and feed on the plant and secrete honeydew, which raises the risk of fungal diseases and can attract other pests, such as ants. You may see a black sooty mold grow on the sticky honeydew.
Whiteflies hatch from tiny, cone-shaped eggs into small scale-like insects that can travel along the plant's stems. The scales molt into nymphs, which then go through several more growth stages before going into a brief resting stage prior to emerging as adult flies. During almost every step of their development, the insects continue to feed on the plant.
The whole lifecycle takes only about 18 days, but this varies, depending on the temperature. In warmer weather, they reproduce more quickly, and in colder weather, the growth cycle is considerably slower.
7 Ways to Get Rid of Whiteflies on Houseplants
Like most pests, the best control for whiteflies is a strong defense. Healthy, vigorous plants are less susceptible to infestation than weak, underpotted, and stressed plants. As a general rule, make sure your plants are healthy, and you're less likely to attract whiteflies in the first place.
If you see whiteflies on your indoor plants, there are several control options. Mechanical controls are the first option to try, since these insects are notorious for developing resistance to pesticides, even organic products.
Vacuum the Insects
Use your vacuum cleaner's hose attachment to sucks up adult whiteflies (but be careful not to damage the plant). Make sure that any newly hatched whiteflies can't escape from your vacuum bag.
Spray With Water
For plants sturdy enough to take this treatment, you can put the entire potted plant in the sink and spray it thoroughly with the faucet sprayer. This often dislodges most of the whitefly adults, larvae, and eggs. Make sure to examine and spray each leaf.
Use Sticky Traps
The same sticky tape that works for houseflies can be used for whiteflies. Hang it from the infected plant if possible, and follow label directions. Sticky traps erected in pots serve the same function.
Spray With Insecticidal Soap
Buy insecticidal soaps, such as Safer's Insecticidal Soap, or make your own by using a plain dish detergent such as Ivory Liquid. Try to find a product free from perfumes and additives that might harm plants. Mix the soap in a weak concentration with water (starting with 1 teaspoon per gallon and increasing as necessary). Spray on plants. This will help control the population but it's unlikely to wipe them out completely.
Use Neem Oil
Neem oil is derived from the neem tree. In addition to its insecticidal properties, neem oil is also a fungicide and has systemic benefits, meaning that some of the oil is absorbed by the plant, offering persistent protection. According to the Environmental Protection Association, neem is safe for use on vegetables and food plants as well as ornamentals. Like insecticidal soap, neem is useful for controlling whitefly populations but might not eliminate the problem completely. Several applications may be necessary.
Make Your Own Pesticide
An all-purpose insect spray can be created by combining one garlic bulb, one small onion, and 1 teaspoon of cayenne pepper in a food processor or blender and process into a paste. Mix into 1 quart of water and steep for one hour. Strain through a cheesecloth and add 1 tablespoon of liquid dish soap. Mix well and use the concoction as a leaf spray. The mixture can be stored for up to one week in the refrigerator.
Use Pyrethrin Spray
While synthetic chemical pesticides should generally be avoided for indoor plants, pyrethrin sprays are fairly safe to use, as the active ingredient is an extract from chrysanthemum flowers. However, some of these pesticides, usually labeled pyrethroids, add chemical components to the pure pyrethrin to improve the function of the pesticide. These cannot be considered organic pesticides, so they should be used very cautiously.
Before using any pesticide, read label directions carefully and make sure it is intended for use to control whiteflies.
While pure pyrethrin pesticide is regarded as organic and is not toxic to mammals, it is decidedly toxic to fish and other aquatic life and should not be used where it can reach water supplies. Pryrethrin may also kill some of the beneficial insects that eat whiteflies, and over time, whiteflies may develop tolerance to pyrethrin if it is overused.
What Causes Whiteflies?
Whiteflies can infest just about any green growing plant in warm conditions, which is why they are more common in greenhouses and on indoor houseplants. They will be less likely to be a problem for plants growing in cooler conditions, or in outdoor settings, where natural predators can control them. Whiteflies seem to be more common on plants with smooth, soft leaves.
How to Prevent Whiteflies
Inspect any plants before you bring them into your home. Isolate them for a few days, well separated from other plants. Spray any infested plants with pyrethrin or neem oil outdoors before bringing them into your home. Once they are in their permanent indoor locations, inspect each plant regularly, and pick off any leaves with visible whitefly infestations.
Where possible, bring plants outdoors during the summer, where natural predators, such as ladybugs and lacewings, can feed on whitefly larvae. Give the plants a carefully targeted spray with pyrethrin or neem oil before bringing them back indoors for winter.
Some experts feel that too much nitrogen fertilizer makes a plant more attractive to whiteflies, so reducing the feeding of susceptible plants may be a strategy to try. Some plants produce an odor that seems to repel whiteflies, including mint, cilantro, and sage; careful companion planting may help control whiteflies.
Do Whiteflies Bite?
These are piercing/sucking insects, but whiteflies don't have mouthparts capable of piercing human skin; they feed only on plant tissues.
Are there Natural Predators of Whiteflies?
In a well-balanced outdoor setting, there are many natural predators of whiteflies, both in their larval and adult phases. Insects that feed on whiteflies include lacewings, ladybugs, dragonflies, and parasitic wasps. Some insect-eating birds will also eat whiteflies. Hummingbirds, for example, are known to feast on whiteflies. It is hard to nurture predators for indoor plants, but an occasional ladybug on your potted houseplants should be considered a good sign.
How Long Do Whiteflies Live?
The entire lifecycle of the whitefly lasts only about 18 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.