Whiteflies are nothing if not prolific. These tiny, heart-shaped flies rest in large numbers on the undersides of leaves, and when the plant is disturbed or brushed up against, the flies will fly out in a great, sudden cloud.
Whiteflies are a common problem in greenhouses, warm climates, and indoors. They cannot tolerate cold weather, but an indoor whitefly infestation can quickly spiral out of control. It's best to treat whiteflies at the first sign of infection.
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 attracting other pests.
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 then emerging as adult flies. During almost every step of their development, they continue to feed on the plant.
The whole lifecycle takes about 30 days, but this varies depending on the temperature. In warmer weather, they reproduce more quickly, and in colder weather, their growth cycle is slowed.
How to Get Rid of Whiteflies
Like most pests, the best control for whiteflies is defensive. 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 these annoying critters in the first place.
If you see whiteflies on your indoor plants, there are several control options:
- Vacuum them away: Use your vacuum cleaner's hose attachment to hoover 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.
- Sticky tape: 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.
- Insecticidal soap: Buy insecticidal soaps, such as Safer's Insecticidal Soap, or make your own by using a 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 a 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.
- Neem oil: Neem oil is derived from the neem tree. In addition to its insecticidal properties, neem is also a fungicide and has systemic benefits, meaning the plant absorbs it so it can control insects it doesn't directly contact. 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.
- Kitchen insect spray: This all-purpose insect spray was developed by the editors of Organic Gardening magazine. To make a batch, combine 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. The mixture can be stored for up to one week in the refrigerator.