Can I Spray Soapy Water on My Tomato Plants?

Soap water is regarded as a holy grail among gardeners. It is believed to deter pests like aphids and beetles.

But won’t the soap water turn toxic to plants? How much soap water is safe for tomato plants? And how often you’re allowed to use soap water on plants?

With this article, let’s end this myth or fact.

For busy gardeners, here is the quick answer.

You can spray soapy water on tomato plants to eliminate pests like aphids. But make sure you’re not using chemical-incorporated dish soap. It may strip the wax layer of leaves, and your tomato plant can be prone to diseases.

Apart from being inexpensive, soapy water is non-toxic to birds and animals. Unlike other insecticides, dish soap water won’t leave a harsh residue.

However, you should ensure you’re not using chemical-included dish soap on tomato plants.

How Does Soap Water Impact Insects?

soapy water for tomatoes

A working theory states that spraying soapy water on insects makes them suffocate, eventually killing them.

Fatty acids in soap water remove the protective layer on these pests, leaving them to dry and die.

Soap water disrupts the cellular membrane of the pests and removes the protective waxes from them.

However, only small, soft-bodied insects like aphids, mealy bugs, whiteflies, spider mites, earwigs, thrips, and leafhoppers are susceptible to soapy water.

It ensures that helpful insects like pollinators aren’t harmed by soapy water.

Occasionally, this homemade insecticide can help to get rid of boxelder bugs.

Note: You should use liquid soap diluted with water to spray on insects. This homemade insecticide is effective only when sprayed directly on the insect and stays effective for a short time.

You can rinse the tomato plant’s leaves with water after the soap water dries to avoid damaging them.

Can I Spray Soapy Water on Tomato Plants?

Yes, you can spray tomato plants with soapy water. This homemade insecticide solution can deter small, soft-bodied insects when sprayed directly on them.

Liquid soap and water are two home-available ingredients that can be turned into a weapon to deter insects from tomato plants.

Helpfully, they won’t harm pollinators and other helpful insects in the garden.

This 2-ingredient home insecticide is safe for birds and pets. And it dries off quickly, so you don’t have to worry much after using it.

Important: Soapy water can only help to deter small insects, while large-bodied insects like beetles and caterpillars are unlikely to be affected by this insecticide.

Check this: Why Are Bottom of Tomatoes Turning Black?

How to Apply Soapy Water on Tomato Plants?

As soap water dries out quickly, you should aim and coat the insect’s body to be effective. Only this can break the protective wax layer on insects and dehydrate them to death.

It would help if you turned tomato leaves to find a bunch of these small-bodied insects.

As these small insects collide with each other, spray with high pressure to knock them off your tomato plants.

Soap water needs to touch the insects to be effective. You’re wrong if you spray it on empty leaves and assume it will prevent new insects.

This insecticide dries out with time, so spray soapy water on tomato leaves with aphids or other small insects.

Before using soapy water on tomato plants, test on 2-3 leaves to ensure safety and effectiveness.

How Often to Spray Soapy Water on Tomato Plants?

You can use soapy water on plants once every 5-7 days. Repeated use can sometimes burn out tomato leaves.

Soap water can strip the protective layer from the leaves, making them prone to diseases.

In case of serious infestation, spray soapy water with high pressure every 4 days and wash the tomato plant after the insecticide dries.

How to Prepare Soapy Water at Home?

You can purchase insecticide solution from the store or make it home.

But, while preparing your insecticide, ensure you won’t aim for more than 2% of soap solution.

  • Take 1 gallon of water, 2 ½ tbsp of pure-castle liquid soap, and 1 tablespoon of vegetable oil (optional).
  • Mix the ingredients thoroughly in a container and pour it into a spray bottle.
  • Your homemade soap water is ready. Spray it on plant leaves to get rid of aphids.

Use distilled water, as hard water can reduce the effectiveness of the soap water solution.

Ensure to mix only liquid dish soap free from harmful chemical ingredients.

Also Read: How to Use Epsom Salt for Tomatoes?

What kind of soap or dishwasher should be used?

High concentrations of soapy solution can burn tomato plant leaves. So you’re advised to dilute it with 1 gallon of distilled water.

To make your insecticide more effective, use liquid soap with essential oils. For instance, pure castile liquid soap with peppermint, lavender, or eucalyptus is best.

Essential oils like peppermint, lavender, and eucalyptus are known to naturally repel fleas, moths, spider mites, aphids, and whiteflies.

However, you must test this insecticide on a few leaves before spraying it on the whole tomato plant.

Can soap water keep pests (bugs and insects) away?

It is a natural pesticide that you can prepare at home using just 2 ingredients: liquid soap and water. It does kill certain garden pests, but soapy water has little impact on larger insects.

Spraying diluted liquid dish soap with water on pests can help suffocate soft-bodied insects like aphids, mites, and mealybugs. It disrupts the cell membranes of pests, resulting in dehydration and, eventually, death.

To ensure safety, use 2 tablespoons of mild liquid dish soap in 1 gallon of water.

Before spraying it on tomato plants, as mentioned above, you should test it on 2-3 plant leaves and ensure they aren’t discoloured. Brown leaves show that the soapy solution might have harmful chemicals or a high concentration of soap.

You can rinse tomato plants to remove soap residue after a few minutes.

Also Read: Can You Eat Tomatoes with Black Spots?

Is it Safe to spray soap and water on tomato plants?

Though it is safe to use soapy water on tomato plants, you should know the possible risks associated with this insecticide.

Repeated use of soap water can strip the natural oils of leaves, exposing them to harmful diseases.

Also, a high concentration of soap solution can burn tomato plant leaves.

List of Plants that are sensitive to soapy water

Though many gardening experts recommend using this homemade insecticide to deter small-bodied insects, certain plants are susceptible to soap water.

You should avoid using this solution on such plants, namely, sweet peas, hawthorn, chrysanthemum, Easter lilies, jade plants, begonia, zebra plants, ornamental ivy, maidenhair fern, certain palm, plum, and cherries.

Alternatives to Soap and Water to Kill Bugs on Tomato Plants

If you’re afraid of any possible risk to tomatoes, then you can opt for alternatives which include:

  • Neem oil to get rid of bugs on tomato plants. You can make neem oil at home or get one from the store to spray it on pest-affected plants.
  • Diatomaceous earth.
  • Garlic spray. Steep garlic in water and strain it after a few hours. Use the obtained water to deter pests.
  • Companion plants like marigolds, nasturtium, and basil are known to repel pests.
  • These companion plants also attract beneficial insects that can help you to get rid of insects.


Using soapy water on tomato plants is one of the most inexpensive and effective ways to eliminate aphids and whiteflies on tomatoes.

However, don’t use a highly concentrated soap solution. Dilute 2 tbsp of mild liquid soap with 1 gallon of water.

Aim on insects to spray soapy water.

Fatty acids in this insecticide break the protective layer on insects and leave them vulnerable to dry and die.