How to Get Rid of Whiteflies on Tomato Plants

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To keep tomato plants healthy and to ensure they produce a good crop of tomatoes, it's important to check them daily for any signs of pests or diseases. Image: © Jeremy Bezanger
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Whiteflies are tiny sap-sucking insects. They are destructive to most agricultural crops especially warm-weather vegetables including tomatoes, peppers and eggplants.

Tomatoes have soft and tender leaves so whiteflies can suck the plant sap easily with their piercing type mouthparts and inject toxin to the plant. As a result, the plant becomes weak, droopy and the leaves start yellowing and curling.

Also, whiteflies can act as a vector to spread many viral and fungal diseases. So, if you want to get a good yield and save your tomato plant, you’ll need to know how to kill whiteflies if your plants suffer an infestation.

Of course, in an ideal world we would rely on natural predators such as ladybugs, female beetles, parasitic wasps like Encarsia formosa, lacewings, hummingbirds, and dragonflies to control the whitefly populations. They feed or lay eggs on the whiteflies and kill them. But as every gardener knows, we can’t always rely on nature to help us out, and we have to intervene ourselves.

There are many methods to deal with whiteflies, and in this article I will give some step-by-step recipes of the most effective methods to get rid of whiteflies on tomato plants.

How to Identify Whiteflies

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An infestation of whiteflies on the underside of tomato leaves. If left unchecked, this common pest will destroy the tomato plant. Image: © Nigel Cattlin

Firstly we need to make sure that we correctly identify the pests as whiteflies. They are small yellow-bodied insects that have powdery white-colored wings. They hang and lay eggs on the underside of tomato leaves. They can produce a sticky substance on the back of the leaves colloquially known as ‘honeydew’. Honeydew causes sooty mold on the leaves and stems of the tomato plants.

You may also find ants on your tomato plants because they are attracted to the sweet honeydew that is produced by whiteflies. So, check the underside of the leaves, and if you notice white tiny insects and nymphs with sticky substances, like the ones shown in the photographs, then it is time to take action.

6 Effective Methods of Getting Rid of Whiteflies on Tomato Plants

Early morning and evening are the best times to treat tomato plants. First, spray fresh water on the plants with a watering hose or sprayer. It will help to eliminate some eggs and nymphs. Then you will need to apply some organic or chemical sprays as detailed below.

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A close-up of four whiteflies sucking plant sap on the underside of a tomato plant leaf. Image: © Floki

Method 1: Organic Insecticidal Soap Spray

Items required:

  • Insecticidal Soap
  • Vegetable oil
  • Water
  • Spray bottle

Procedure:

  1. Measure out two and a half tablespoons of liquid insecticidal soap and the same quantity of vegetable oil.
  2. Mix the soap and oil into four liters (about a gallon) of water and shake well.
  3. Pour into a spray bottle and apply to the affected upper and lower leaves of the tomato plants.

If insecticidal soap is not available where you live, then you can use ordinary liquid soap, but it may not be as effective. You can also buy insecticidal soap online from companies like Amazon. Brands like Garden Safe Insecticidal Soap Insect Killer, Bonide Ready-to-Use Insect Soap, Safer Brand Insect Killing Soap, and Natria Insecticidal Soap are the most popular and effective for whiteflies on tomatoes.

Method 2: Organic Neem Oil Spray

Items Required:

  • Neem oil
  • Water
  • Spray bottle

Procedure:

  • Mix two tablespoons of neem oil into four liters of water.
  • Shake well and spray on the tomato plant.

You can also add mild dish soap into the mix to increase the efficiency of neem oil. If you can’t find neem oil where you live, it’s also available online in a ready-to-spray formula. The best neem sprays for whiteflies are Natria Neem Oil Spray for Plants, Bonide Ready-to-Use Neem Oil, and Monterey Neem Oil Ready-To-Use Insecticide.

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Using a simple hand sprayer to apply insecticide to a tomato plant to treat and prevent insects. Image: © Andrii Salomatin

Method 3: Garlic Spray

Items Required:

  • 1-2 garlic bulbs
  • Mild liquid soap
  • Water
  • Spray bottle

Procedure:

  1. Peel the garlic and separate the bulbs into cloves.
  2. Put them into a blender and add one cup of water.
  3. Blend them well and pour them into a liter of water (about a quart).
  4. Add one tablespoon of liquid soap.
  5. Pour the solution into a sprayer and apply it to the plant.

Remember the blend must be liquid otherwise it will block the nozzle of the sprayer. You can also add a small onion and a teaspoon of powdered cayenne pepper to make a more powerful insecticide.

Method 4: Horticultural Oil Spray Insecticide

Items Required:

  • Mineral or horticultural oil
  • Liquid soap
  • Water
  • Spray bottle

Procedure:

  • Mix 6-8 tablespoons of oil per liter of water.
  • Add one tablespoon of soap into the solution.
  • Shake and pour the solution into a sprayer to apply.

Mineral and horticultural oils are also manufactured commercially in both ready-to-use and concentrate formulae. Bonide All Seasons Horticultural Oil Spray and Monterey Horticultural Oil Concentrate are recommended to get rid of whiteflies on tomatoes.

Method 5: Yellow Sticky Whitefly Trap

Yellow sticky whitefly traps are also an effective and popular non-toxic method to get rid of moths, thrips, leaf miners, gnats, and whiteflies.

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Weak and droopy leaves of a tomato plant that has been infested with whiteflies. Image: © Elena Kitch

Yellow is the favorite color of these insects, so the insects are attracted by the color of the trap. The insects cannot control themselves and keep flying towards it. Finally, the adhesive substance holds the insects and they will die in the trap.

Method 6: Using Commercial Insecticide

When it comes to controlling pests on plants that are producing fruits or vegetables that we eat, we all prefer to use something that is organic and non-toxic. But sometimes an infestation is so bad that the only alternative to pulling out the plants and starting again is to use a chemical insecticide. There are hundreds of insecticidal brands available in the market today. Most are effective but none are as safe as the non-toxic solutions described above.

Pyrethrin or spinosad-based insecticides are the safest commercial insecticides to use on tomatoes to kill whiteflies because they are considered organic. But it’s important that the insecticide make direct contact with the insects, so all parts of the plant need to be thoroughly sprayed.

Other more toxic chemical insecticides such as malathion, imidacloprid, and diafenthiuron can kill whiteflies without harming the tomato plants, but it’s very important to follow the instructions on the label of the insecticide before spraying.

whiteflies-on-tomatoes-pressure-sprayer
When spraying insecticides on tomato plants, it’s important that both the top and undersides of the leaves are covered, so a pressure sprayer is better than a hand sprayer because it can more effectively get under the leaves. A few days ago, one of my tomato plants was badly affected by whiteflies, but now after spraying it is reviving day by day. Image: © Starder

High concentrate insecticides can burn the leaves of tomato plants, so first apply the spray on a small number of leaves and wait overnight. If you don’t notice any signs of burning, then you can proceed to spray the tomato plants entirely the next day. But if you notice any wilting or burning signs, dilute the solution by mixing more water.

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