Whiteflies

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D. Kucharski, K. Kucharska/Shutterstock
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How to Identify and Get Rid of Whiteflies on Plants

The Editors
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Noticing tiny, white, fly-like insects on your plants? You may be dealing with a whitefly infestation. Here are tips on how to identify, control, and get rid of whiteflies!

What Are Whiteflies?

Whiteflies are soft-bodied, winged insects closely related to aphids and mealybugs. Despite their name, whiteflies are not a type of fly, though they do have wings and are capable of flying.

Whiteflies can be as small as 1/12 of an inch, are somewhat triangular in shape, and are often found in clusters on the undersides of leaves. They are active during the day and will scatter when disturbed, so they can be easier to spot than some nocturnal insect pests.

There are hundreds of species of whiteflies, but most affect only a small number of host plants. However, there are a few whitefly species that affect a wider range of plants, which make them the most problematic in horticulture. These whitefly species include the greenhouse whitefly, bandedwinged whitefly, giant whitefly, and silverleaf whitefly, among others. Silverleaf whiteflies, which are slightly smaller and more yellow than other whiteflies, are especially common in the southern United States. 

Where Are Whiteflies Found?

In USDA Zone 7 and colder, whiteflies are not able to survive winter outdoors, so their presence tends to be limited to indoor plants or greenhouse environments. However, if outdoors plants are bought from an infested greenhouse, whiteflies may become a seasonal outdoor garden pest. (Always inspect plants before bringing them home!) 

In warmer regions, whiteflies are capable of overwintering and reproducing outdoors throughout the year, so they can be a problem for both indoor and outdoor plants.

You’ll often start to see whiteflies in mid- to late-summer when it gets warm and humid.

Which Plants Are Susceptible to Whiteflies?

Whiteflies can be found on a wide variety of plants, from ornamental flowers to warm-weather vegetables, including tomatoes, eggplant, peppers, and okra. Some species may attack sweet potatoes, plants from the cabbage family, and citrus trees. Indoors, they will feed on most common houseplants, especially those with soft, smooth leaves.

Identification

How to Identify Whiteflies

Like aphids, whiteflies use their piercing mouthparts to suck up plant juices and, in turn, produce a sticky substance known as honeydew. Honeydew left on its own can cause fungal diseases such as sooty mold to form on leaves.

With heavy whitefly feeding, plants will quickly become extremely weak and may be unable to carry out photosynthesis. Leaves will wilt, turn pale or yellow, growth will be stunted, and eventually leaves may shrivel and drop off the plant. 

Honeydew is a sign that the whiteflies have been feeding for several days. You might also see ants, which are attracted to the sweet honeydew. 

Where to Find Whiteflies on Plants

Whiteflies tend to prefer to feed on new growth, so check around any newly unfurled leaves first.

Check the undersides of leaves—especially around the veins—for white insects, even if they aren’t immediately visible, and feel leaf surfaces for sticky honeydew. If the whiteflies are feeding, they’ll suddenly all fly off the leaves in a swarm, so it’s very obvious.

You may also find eggs laid on the undersides of leaves. This is the beginning of a new generation! When the eggs hatch, the larvae will look like teeny white ovals without legs; they don’t move but they immediately start sucking the plant juice. This is why gardeners often miss whiteflies until it’s too late. Adult females can produce up to 400 eggs, which hatch in about one week to a month after laying. They are usually laid in a circular pattern. Eggs are pale yellow when newly laid and brown when about to hatch.

whiteflies-eggs-control-identify.jpg
Whiteflies congregate on the undersides of leaves and lay their tiny white eggs in this secure spot. Photo Credit: University of Florida.
Control and Prevention

How to Get Rid of Whiteflies

To control whiteflies, there are various solutions and traps that you can use. The biggest tip is: start early! In the mornings and evenings, as you wander the garden or tend to your houseplants, check the back of the leaves for eggs or notice when little bugs “fly away” as you approach your plants.

  • Always start with blasting whiteflies (as with aphids and many other insect pests) with your watering hose or a spray bottle. This will cause them to scatter and will dislodge nymphs and eggs to some extent.
  • Consider spraying your plants’ leaves with an insecticidal soap, following the directions on the packaging. Be sure to spray the undersides of leaves, too. Follow up 2 or 3 times, as necessary. 
    • Tip: Spray plants in the evening when temperatures are cooler, as mid-day heat may cause an adverse reaction in your plant. Plus, spraying in the evening allows you to avoid accidentally spraying any pollinators or beneficial insects.
  • According to the National Gardening Association, the following simple homemade mixture should be helpful to control and deter whiteflies: Use a mix of dish soap and water. A good squirt of soap to a gallon of water should work. As mentioned above, only spray in cooler temperatures; late in the day is best. The NGA mixture is a pretty benign combination, and whiteflies are nearly impossible to get rid of, so it’s best to try more preventative tactics first, as mentioned below.
  • If all else fails and your whitefly population is persistent, you can (carefully) use a handheld vacuum every few days to remove them from your plants. This gets rid of both nymphs and adults. Just be sure NOT to empty your vacuum into a trash can inside your home afterward!

How to Prevent Whiteflies

  • Your first line of defense should be inspecting all plants for pests before you bring them home, as well as keeping any new additions away from the rest of your plants for a period of time. This will allow you to identify and curtail any pest or disease issues that appear.
  • Keeping natural predators around will prevent whiteflies from ever exploding in population. For this reason, avoid using insecticides. Ladybugs, spiders, green lacewing larvae, and dragonflies are a few of many beneficial insects that can control a whitefly population. Hummingbirds are another natural predator. Try creating a habitat that will attract dragonflies and damselflies (which also helpfully eat mosquitoes) or beautiful hummingbirds.
  • When it comes to whiteflies, avoid chemical insecticides; they’re usually resistant and all you end up doing is killing the beneficial insects—their natural predators—and the insects that pollinate the garden for a better harvest!
  • Mulch early in the season with aluminum reflective mulch, especially around tomatoes and peppers. The reflective mulch makes it challenging for whiteflies to find their preferred host plants. 
  • Set out yellow index cards coated with petroleum jelly to monitor whiteflies, especially when it comes to tomatoes, peppers, sweet potatoes, or cabbage crops. A half-and-half mixture of petroleum jelly and dish soap, spread over small boards painted bright yellow, is sticky enough to catch little whiteflies, too. To whiteflies, the color yellow looks like a mass of new foliage. The bugs are attracted to the cards, get stuck in the jelly, and die.
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