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Flip over a leaf and there they are. Tiny white specks that explode into a cloud when you disturb the plant. That’s whiteflies, and by the time you notice them, you’ve got a problem. They reproduce fast, feed on plant sap, and leave behind sticky honeydew that attracts mold and other pests.
Whiteflies cluster on the undersides of leaves, sucking nutrients and weakening the plant from the bottom up. A light infestation is annoying. A heavy one can kill tomatoes, peppers, and ornamentals in a matter of weeks.
The trick is hitting them from multiple angles. One method alone won’t cut it. Here’s what actually works.
1. Hang Yellow Sticky Traps
Whiteflies are attracted to bright yellow. Hang sticky traps near infested plants (about 6 inches away from the foliage) to catch adults before they lay more eggs. This won’t eliminate an infestation, but it knocks down the population and gives you a read on how bad things are.
Check the traps every few days. If they’re covered in whiteflies, you’ve got active breeding. If they’re empty, you’re winning.
2. Hose Them Off with Water
A strong spray from the garden hose knocks whiteflies, nymphs, and eggs off the leaves. It’s basic but effective, especially if you catch the infestation early. Hit the undersides of the leaves where they cluster.
Do this in the morning so the plant has time to dry before nightfall. Wet foliage overnight invites fungal problems, which is the last thing you need on top of whiteflies.
3. Vacuum Them Off (Yes, Really)
A handheld vacuum works surprisingly well for whiteflies. Gently run the nozzle under infested leaves to suck up the adults. They’ll scatter when you approach, so move slowly.
Empty the vacuum immediately into a sealed bag and toss it in the trash. Otherwise, they’ll just crawl back out. This is a good option for indoor plants or greenhouse setups where you can’t blast them with a hose.
4. Spray Insecticidal Soap
Insecticidal soap kills whiteflies on contact by breaking down their outer coating. Spray the undersides of leaves thoroughly, where the nymphs and adults hide. You’ll need to reapply every 5 to 7 days because soap doesn’t kill eggs.
Make sure you’re using actual insecticidal soap, not dish soap mixed with water. Dish soap can burn plant leaves, especially in hot weather.
5. Make a DIY Soap Spray
If you want a homemade version, mix 1 tablespoon of pure castile soap (like Dr. Bronner’s) with 1 quart of water. Spray it on the undersides of infested leaves in the early morning or late evening when temperatures are cooler.
Test on a small section first. Some plants are more sensitive to soap sprays than others.
6. Apply Neem Oil
Neem oil disrupts the whitefly life cycle by preventing larvae from molting into adults. Mix neem oil according to the package directions (usually 2 tablespoons per gallon of water) and spray the entire plant, focusing on leaf undersides.
Neem needs repeated applications every 7 to 10 days to work. It’s not a knockdown spray. It’s a slow grind that stops reproduction over time.
7. Use Horticultural Oil
Horticultural oils (like summer oil or dormant oil) smother whitefly eggs, nymphs, and adults. They coat the insects and suffocate them. Apply in the cooler parts of the day to avoid burning foliage.
Don’t use horticultural oil within 2 weeks of a sulfur-based fungicide. The combination can damage plants.
8. Dust with Diatomaceous Earth
Food-grade diatomaceous earth (DE) is a fine powder made from fossilized algae. It shreds the exoskeletons of whiteflies and other soft-bodied insects, causing them to dehydrate and die. Dust it lightly on the undersides of leaves and around the base of the plant.
Reapply after rain or watering. DE only works when dry. Wear a mask when applying it, as the powder can irritate your lungs.
9. Remove Heavily Infested Leaves
If a plant is covered in whiteflies, strip off the worst leaves and bag them immediately. This cuts down the breeding population fast. Don’t compost infested foliage. Toss it in the trash or burn it if local regulations allow.
Don’t remove more than 20-30% of the plant’s foliage at once, or you’ll stress it further.
10. Plant Marigolds and Basil Nearby
Whiteflies avoid marigolds and basil. Plant them near tomatoes, peppers, and other whitefly magnets to create a natural buffer. It’s not a silver bullet, but it helps reduce egg-laying activity in the area.
Marigolds also attract beneficial insects like ladybugs and lacewings, which eat whitefly nymphs.
11. Attract Predators with Sweet Alyssum
Sweet alyssum attracts parasitic wasps, hoverflies, and other predators that feed on whitefly eggs and larvae. Plant it as a ground cover near your vulnerable plants. It’s low-maintenance and flowers most of the season.
The more beneficial insects you can establish in your garden, the less you’ll have to spray.
12. Avoid Over-Fertilizing
Whiteflies are drawn to lush, nitrogen-rich growth. If you’re dumping synthetic fertilizer on your plants, you’re basically setting out a buffet. Back off on the nitrogen and focus on balanced, slow-release fertilizers.
Healthy plants can tolerate a light whitefly presence. Over-fertilized plants just give them more to eat.
13. Use Reflective Mulch
Reflective aluminum mulch confuses whiteflies and reduces egg-laying on nearby plants. Lay strips of aluminum foil or reflective plastic mulch around the base of infested plants. The reflected light disorients the adults.
This works best early in the season before whiteflies establish large colonies. Once they’re dug in, mulch alone won’t save you.
Whiteflies are persistent, but they’re not invincible. Combine a few of these methods and stay consistent. Most infestations break within 2 to 3 weeks if you keep the pressure on.