How to Identify and Get Rid of Whiteflies

The common name "whitefly" applies to more than 1500 species from the family of insects that includes aphids and mealybugs. Many different types of whiteflies can infest plants, depending on where you live and the type of plant being affected. Although these heart-shaped flies are tiny, no more than 1/10 inch long, dozens will emerge in a cloud from an infested plant when the host plant is bumped or moved. This is the most obvious sign you have a whitefly infestation.

Whiteflies are sap sucking insects that weaken plants by piercing leaves and stems and feeding on plant nutrients. The entire life cycle of one generation takes between 16 and 22 days and can quickly spiral out of control with overlapping generations as long as conditions remain favorable. Whiteflies thrive in warm temperatures and quickly reproduce on houseplants and in greenhouses. They also are attracted to these warm season garden vegetables:

• Eggplant
• Okra
• Bell Pepper
• Cabbage
• Tomato
• Sweet Potato
• Sweet Corn

A whitefly infestation can quickly spiral out of control, so it's best to treat whiteflies at the first signs of infestation.

How to Identify Whiteflies

Adult whiteflies resemble tiny moths, somewhat triangular shaped with yellow heads. Eggs are white and cone-shaped, laid in a circular pattern on the undersides of leaves close to the veins. These hatch into oval shaped nymphs that move along the plant surface to a feeding spot. The insect remains there through several life stages before emerging as a winged adult. During almost every step of their development, the insects continue to feed.

If you suspect whiteflies, give the affected plant a gentle shake. The tell-tale cloud of insects will fly up out of the foliage to confirm your suspicion. An infestation can develop pretty quickly but you may be able to get control earlier by watching for small, gnat-like insects flying around your plants. Whiteflies prefer to feed on new growth and adults can be spotted moving among plants. Check leaves and stems for sticky residue. This is called honeydew and is present where sap sucking insects feed. Honeydew also attracts ants so if you find ants on plant foliage, it may be a sign whiteflies are active.

What Causes Whitefly Infestations

Pests are drawn to plants that are already stressed so keeping your plant collection hardy and healthy is the best defense against a whitefly problem. Whiteflies are also attracted to plants with smooth, soft leaves. Here are some conditions that create an environment particularly appealing to whiteflies.

Nitrogen Rich Soil: Nitrogen produces plenty of new foliage growth which is where whitefly prefers to feed. This is a particular problem when growing seedlings in a greenhouse; fertilizing houseplants with high nitrogen products; and during early growth in the vegetable garden when plant energy is focused on developing foliage.

Hot, Dry Weather: Whiteflies thrive in warm temperatures between 80 and 90 degrees F. This level of heat is more consistent in a greenhouse environment; however, dry conditions in your home or vegetable garden also attracts these insects to your plants as a source of moisture.

Lack of Natural Predators: This problem is more likely to be present in the vegetable garden than in your home and may or may not be an issue in a greenhouse depending on the insect controls applied. Overuse of broad spectrum pesticides can lead to the elimination of their natural predators, since these products kill indiscriminately. Adding flowers and companion plants in the vegetable garden attracts beneficial insects to help control pest populations naturally.

Whitefly Plant Damage

Nymphs and various larval stages attach to the plant's soft tissues, feed on the plant and secrete honeydew, which can cause fungal disease as well as attract other pests like ants. Black sooty mold can develop on honeydew secreted by whiteflies.

They seldom actually kill a plant but infestations cause considerable damage including chlorosis, defoliation, and stunting. This is a particular concern in greenhouses where conditions allow for concurrent cycles of insects to infest a greater number of plants in close proximity. The entire life cycle varies depending on temperature but it's common for insects in all six growth stages to be present on a plant simultaneously. In warmer weather, whiteflies reproduce quickly, but in colder weather the life cycle unfolds more slowly.

9 Ways to Get Rid of Whiteflies on Plants

There are a number of ways to control whiteflies. Mechanical controls are the first option because these pests quickly develop resistance to pesticides, even organic products.

Spray With Water

A strong spray from a garden hose can knock down many types of sap sucking pests including whiteflies and aphids. For houseplants, 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. Attach it to stakes to place in the garden. Hang sticky traps on infected houseplants or stake them in pots. Strips can also be hung or placed on stakes in greenhouses.

Spray With Insecticidal Soap

Use premixed insecticidal soap, or make your own by using a plain dish detergent. Try to find a product free from fragrance and additives that might harm plants. Mix the soap in a weak concentration with water (starting with one teaspoon per gallon of water and increasing as necessary). Spray on plants. This helps control the population but it's unlikely to completely eradicate them.

Use Neem Oil

Neem oil has insecticidal properties and also works as a fungicide. The oil is absorbed by the plant, offering some persistent protection. According to the Environmental Protection Agency (EPA), neem oil 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 Insect Spray

You can create an all-purpose insect spray by combining one garlic bulb, one small onion, and one teaspoon of cayenne pepper in a food processor to make a paste. Mix the paste into one quart of water and steep for one hour. Strain through cheesecloth and add one 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 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 pure pyrethrin to improve the function of the pesticide. These cannot be considered organic pesticides, so use them cautiously in an indoor environemnt.

Before using any pesticide, read label directions carefully and make sure whitefly is listed as a targeted pest for the product.

Vacuum the Insects

If whitefly has infested your houseplants, use your vacuum cleaner hose attachment to suck up adult whiteflies. Eliminating adults interrupts the life cycle and helps bring the population under control. Use this method carefully to avoid damaging the plant.

Encourage Natural Predators

Natural predators of whiteflies will keep populations under control in greenhouses and vegetable gardens. Provide good air circulation in the greenhouse with open vents and fans that allow access to whitefly predators. Practice good spacing between garden plants and add flowers and companion plants that attract beneficial insects.

Use Reflective Mulch

Reflective mulches are often silver or may include aluminum that reflect sunlight up into surrounding plants. The ultraviolet rays confuse pests making it difficult for them to locate that particular food source. Mulches work best in an outdoor environment. You could try placing a sheet of aluminum foil under a potted plant to help deflect whitefly.

How to Prevent Whiteflies

Inspect plants before you bring them home. Isolate them for a few days 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, move houseplants outdoors during the summer, where natural predators, such as ladybugs and lacewings, can feed on whitefly larvae. Invite these predators into your yard and gardens by growing flowers that attract them. Give houseplants a carefully targeted spray with pyrethrin or neem oil before bringing them back indoors for winter.

Keep the vegetable garden and greenhouse adequately watered, especially during drought conditions and provide good air circulation with fans, vents and adequate spacing. Reduce the use of high nitrogen fertilizers for susceptible plants.

Plants with strong scent like mints, thyme and sage often repel pests so consider companion planting in the vegetable garden. Fresh or dried leaves of strongly scented plants can also be strategically placed around indoor plants to deter whiteflies and other pests.