There’s nothing quite as lovely as a vegetable garden – but unfortunately, plenty of pests think so too! Whiteflies, or Trialeurodes vaporariorum, are a common pest found on outdoor vegetables and fruits that’s particularly resistant to synthetic pesticides.
This makes it a real problem for farmers as well as home gardeners. Here’s some practical advice on whiteflies prevention and control to help keep your plants healthy, thriving and pest-free.
What are Whiteflies?
They aren’t actually a fly at all! They are small, sap-sucking insects that are similar to aphids, scale and mealybugs. The adults and the nymphs both feed off the sap of the plant, and are usually found in clusters on the undersides of the leaves.
The adults are about 1/16 of an inch long with short antennae and distinctive, moth-like powdery wings, which is how they got their name.
The nymphs (the immature whiteflies) are wingless, flattened and lack visible legs, resembling scale. Whiteflies tend to vary slightly in color from white to pale yellow to an almost transparent appearance.
Where are Whiteflies Found?
Whiteflies are common across the USA, although they cannot survive the winters in states in USDA Zone 7 and colder.
They thrive in warmer, humid weather (outbreaks are typical in mid to late summer) and where natural predators aren’t available, and can breed all year round outdoors in coastal and Southern states, while Northern states can have indoor or greenhouse outbreaks.
Common Types of WhitefliesThe most common types are the greenhouse whitefly (Trialeurodes vaporariorum), sweet potato whitefly (Bemisia tabaci), and giant whitefly (Aleurodicus dugesii).
Although they have different ranges of host plants, they can be dealt with using the same prevention and control measures.
Why is Whiteflies Prevention and Control Important?
Whiteflies lay their eggs on the underside of leaves. When the eggs hatch, the insects pierce the leaf and drink the sap inside. All whiteflies feed in this way, including adults.
Although they don’t attack the fruits of the plant, whitefly damage can quickly kill leaves, causing them to go brown and fall off. This can stunt vegetable growth or even kill the plant.
In addition, whiteflies produce honeydew (just like aphids), which is a sticky, sugary liquid. This covers the plant, attracting other pests and becoming a host for sooty, black mold.
Plants suffering from infestations become discolored, lose leaves, and reduce or lose their vegetable crop entirely. Whiteflies can also transmit diseases to other plants, causing additional damage.
What Plants are Vulnerable to Whiteflies?
Whiteflies typically attack:
- Vegetable crops – Tomatoes, eggplant, okra, peppers, sweet potatoes, cabbages, lettuce, melons, cucumber, and beans.
- Fruit crops – They are less common on fruit crops but have been found to attack citrus trees, grape vines, pomegranates, and avocados.
- Ornamental plants – Some ornamental plants including fuchsia, lantana, gardenia and greenhouse foliage plants.
- Marijuana – Cannabis or marijuana plants are also vulnerable to whiteflies, especially if the plants are grown outdoors or in a greenhouse.
It’s a good idea to protect your plants with a grow tent, and to check plants thoroughly for these pests before bringing them home.
Early Signs of a Whiteflies Infestation
Infestations are more easily dealt with in their early stages, so keep an eye out for:
- Dry, brittle leaves
- Leaves turning yellow
- Sticky residue and black mold on your plants
If you notice any of these signs, turn over the leaves of your plants and check for these tiny bugs or their eggs.
How to Get Rid of Whiteflies
Whiteflies on plants are not easy to get rid of! Some experts recommend immediately removing and destroying infected plants, then waiting a season before you replant.
However, there are a few other things you can try for whitefly treatment.
- Check plants before you buy – Whiteflies are often introduced into a garden through a new plant, so thoroughly check plants before you buy them.
Don’t buy any plants with whiteflies or eggs on them, or that have yellowing or dried out leaves.
- Introduce natural predators – These include pirate bugs, green lacewings, dragonflies, big-eyed bugs, parasitic wasps and ladybugs.
- Do not spray insecticide – These pests are very resistant to pesticide, so all it does is kill off natural predator insects, which will make the infestation worse.
- Whitefly traps – You can usually find these sticky whitefly traps at your local garden center, and they can deter whiteflies from making their new home on your plants.
- Physical removal – Regularly spray the underside of the leaves with a blast of water, or remove infected leaves by hand (put them in the trash or burn them).
- Garlic or neem oil – Spray with garlic oil or neem oil for whiteflies every 2 days as an organic whitefly control treatment. Remember to keep this up for 3-4 weeks to kill adults and eggs.
Mix 1oz/gallon of water and drench the plant, including the underside of the leaves.
- Safer Soap – Safer Soap is an organic whitefly control product that works well on heavy infestations. It is a whitefly treatment that can also be used on aphids, mealybugs, spider mites, leafhoppers and scale. It is safe for beneficial insects.
How to Prevent Whiteflies
Prevention is always better than a cure! You can help prevent an infestation by:
- Healthy plants – Only introducing healthy, pest-free plants into your yard and vegetable garden.
- Before planting – Prepare your vegetable garden with flowering plants to attract natural predator insects and hummingbirds.
- During planting – Plant in early spring or late fall to avoid high-risk periods.
- Mulch – Use an aluminum reflective mulch around vulnerable vegetables and plants. This makes it difficult for the whiteflies to detect the plants and settle on them.
- Place whitefly traps – These sticky traps will attract any nearby whiteflies, giving you an early alert if they arrive in your vegetable garden.
- Chat to your neighbors – Whiteflies can arrive from almost anywhere, so it’s good to spot an infestation early on when it arrives in your neighborhood.
Chat to other vegetable and fruit-growers in your local area so you can all be aware and on the lookout.
Do Ladybugs Eat Whiteflies?
Yes! They are a fantastic beneficial insect for whitefly control and can help prevent infestations on vegetable crops and ornamental plants.
You can encourage ladybugs by planting flowering herbs (tansy, caraway, cilantro, cosmos, scented geraniums and angelica) and by not using insecticidal sprays.
Preserve Your Crops with Whiteflies Prevention and Control
Whitefly damage can devastate a vegetable garden as well as ornamental plants and marijuana plants, and are very challenging to get rid of.
Remember, prevention is better than a cure, so encourage natural predators, plant outside of high-risk periods, use reflective mulch, use a grow tent if you need to, and avoid insecticidal sprays that can kill beneficial insects off.
Watch for yellowing dead leaves and other early signs of an infestation so you can contain it and react quickly, removing these pests by hand, with traps or killing them with organic insect control.
Keeping your eyes peeled for these pests is an essential part of whiteflies prevention and control!