Insecticidal Soap vs Dish Soap for Pest Control

It’s a debate.

Can you use dish soap on plants? Or should you only use insecticidal soap?

Is one better than the other? Is dish soap harmful to use? These are some questions and discussions you’ll find on the Internet about this topic.

I’ve written a detailed guide below so you can learn all there is about using dish soap or insecticidal soap for your plants. And make the best decision for your garden.

Let’s take a look.

What is soap?

Soap comprises several fatty acids, so it works as a surfactant. This means it breaks down the surface tension between two substances. You use soap for cleaning. We can make it with natural ingredients such as vegetable oil, animal fat, or using synthetic chemicals.

You’ll often hear two types of soaps being used in the garden: dish soap and insecticidal soap. Both can take care of some pests on the plants.

Dish soap

Dish soap is the common soap you use at home to remove dirt, grease, and food residue from the dishes. It contains surfactants that break down oil and grease, making it easier to clean.

Dish soap has a higher pH level that makes it more alkaline compared to insecticidal soap. This can be useful to get rid of some pests. But it can also harm the plants if too much is used. Or if it contains chemicals that harm plants.

Some gardeners would say avoid using dish soap on plants because of the risk. Just use insecticidal soap that is made for plants and has a lower chance of damaging them.

Read more:

• Is Dawn Dish Soap Safe For Plants? (Which Variety To Use)

Insecticidal soap

Insecticidal soap has a lower alkaline level compared to dish soap. It is made to use for plants and is safer. It can still harm sensitive plants, so you need to avoid using it in certain cases.

It works by suffocating small-bodied insects and disrupting their cell membranes. It can break down some insects exoskeleton, causing dehydration. So it’s beneficial against pests like aphids, mites, whiteflies, leafhoppers, and mealybugs. Note that insecticidal soap works only when it’s wet.

Insecticidal soaps are considered being among the safest pesticides and leave no harsh residue. They are a natural and environmentally friendly alternative to chemical pesticides. These soaps can be used on most plants without posing a risk to human health or beneficial insects.

When using insecticidal soaps, it is important to follow the label directions carefully and apply the soap solution to both the top and underside of leaves for better control.

Dish soap vs insecticidal soap

Dish soap has higher pH levels than insecticidal soap. So it can kill pests but also harm plants. Insecticidal soap has lower pH levels or alkalinity and so it is milder. We can use it on many plants to get rid of pests.

To give you a better understanding, here’s a comparison between dish soap and insecticidal soap:

Dish Soap	Insecticidal Soap
High alkalinity	Lower alkalinity
Damages plant leaves	Safe for plants
Kills beneficial insects	Does not harm beneficial insects
Not specifically designed for pest control	Formulated for effective pest control

I asked gardeners if they used soap to get rid of pests on plants. Below are the results of the survey. 70% gardeners used dish soap on their plants.

How does soap kill pests?

Soap kills some pests by suffocating them and damaging their cell membranes. It can kill some other pests by breaking down their waxy exoskeleton, causing them to dehydrate. Besides suffocating pests, soaps can also disrupt their ability to reproduce and lay eggs.

Which insects is soap effective against?

Soap can be effective against small, soft-bodied insects such as aphids, whiteflies, thrips, mites, and mealybugs. The soap will suffocate them and damage their exoskeleton, causing them to dehydrate. It will disrupt their cell membranes. Soap is not effective against larger insects, such as caterpillars and beetles.

To ensure effectiveness, the soapy water needs to not just touch the insect but also coat its body. Turning over leaves can help reach insects on the underside, and high-pressure sprays can knock off small-bodied insects from the plant.

It’s crucial to apply the spray when new insect populations appear and start to increase, as spraying soap on leaves when no insects are present does nothing. Remember, soap only works if it contacts the full body of the insect.

List of insects that insecticidal and dish soap will kill.

• Aphids
• Mealybugs
• Earwigs
• Whiteflies
• Grasshoppers
• Harlequin Bugs
• Leafhoppers
• Mites
• Psyllids
• Sawfly Larvae
• Soft Scales
• Spider Mites
• Squash Bugs
• Blossom Thrips

Read more:

• A Pocket Guide To Identify Pests On Vegetable Plants

Safety precautions when using soap on plants

Whether you use dish soap or insecticidal soap, you’ll need to protect yourself and the plants before using it. Let’s look at some safety measures to keep in mind.

1. I would suggest covering your skin with long sleeves, pants, and gloves. Some people may be allergic to the soap and get a reaction.

2. Be careful when spraying the soap solution, so you don’t get it in your eyes or mouth. Spray away from your body and stand upwind to avoid getting in the way.

3. Keep the soap away from children and pets. Store it in a secure location that is out of reach of children and pets. This helps prevent them from accidentally ingesting the soap or spraying it on themselves.

4. Always follow the instructions on the insecticidal soap packaging for the right use and dosage. If using dish soap, follow the right instructions. It may be better to test the soap on a few leaves and leave it for 24 hours to check for any adverse effects.

What are some plants sensitive to soap?

I would not recommend using either dish soap or insecticidal soap on certain sensitive plants. The soap will damage their cell membranes and leave them susceptible to pests and diseases. Some such sensitive plants are azaleas, begonias, fuchsias, geraniums, and impatiens.

I always suggest testing the soap solution on a few leaves and checking after 24 hours. Only continue using the soap if there is no adverse reaction on the plant.

How long does it take soap to work?

Dish soap should start working on pests within 24 hours and you should be able to see the difference in the plants. Insecticidal soap works almost instantly, killing insects as soon as they come into contact with it.

However, you may need to reapply the solution several times to notice a major impact on your plants. This is because you have to make sure all the pests have been killed off, and they may require multiple treatments.

In the most severe cases, an infestation can be taken care of by applying the product just once every three to six days. So, be patient and consistent with your application of dish soap or insecticidal soap, and you’ll see results within a day.

How to use dish soap on plants

Mix 2.5 tablespoons dish soap with 2.5 tablespoons vegetable oil in a gallon of water. Use dish soap that is free from chemicals and any fragrance. If possible, use castile soap that contains non-toxic ingredients.

Add this solution to a spray bottle and shake it well to mix all the materials.

Spray this solution on all the foliage where there are pests. Remember to spray underneath the leaves. Apply the solution on all the leaves where you see pests or damage because of pests.

It’s best to start with the weakest solution possible and only increase the soap concentration if it’s not working. Spray the solution until it drips.

Avoid spraying the solution when the sun is out because it can burn the leaves. The best time is early morning or late evening.

Do not use this spray on plants that may be stressed because of environmental stress such as transplant shock, lack of right temperature, or watering.

Don’t spray the soap if you see beneficial insects such as lady beetles or lacewings on the plant. Wait for a few hours and check again.

Read more:

• How To Make Vegetable Oil Spray For Plants

How often should you use dish soap?

You should only use dish soap once a week and no more because it can be harsh and damage plants if you use too much or too often.

I suggest using dish soap as a treatment option only when you notice pests on the plants. Don’t use it as a method to prevent pests.

This way, you can minimize any potential negative effects on your plants while effectively controlling pests. Remember, moderation is key when using dish soap as an insecticide.

Best dish soap for plants

While we can use dish soap as an insecticidal soap to control certain garden pests, it’s essential to choose the right type of dish soap to minimize harm to your plants. Here’s how to choose the best dish soap for plants:

1. Unscented and Dye-Free: Opt for a dish soap that is unscented and free from dyes. Fragrances and dyes can contain chemicals that may be harmful to plants.
2. Mild Formula: Choose a mild dish soap with a gentle formula. Dish soaps formulated for sensitive skin or labeled as “mild” are typically better options because they contain fewer harsh chemicals.
3. Biodegradable: Look for dish soaps that are biodegradable. This means the soap is less likely to harm the environment and is safer for your plants.
4. Liquid vs. Solid: Liquid dish soap is easier to mix with water to create a diluted solution. Solid or concentrated dish soaps may require more effort to dissolve properly.
5. No Added Antibacterial Agents: Avoid dish soaps that contain antibacterial agents. These chemicals can be more harmful to plants and the environment.
6. Read the Label: Check the label for any warnings or cautions regarding plant use. Some dish soaps may have plant-specific recommendations.
7. Simple Ingredients: Choose a dish soap with simple ingredients. Avoid products with a long list of additives and chemicals.
8. Non-Phosphate: Dish soaps that are phosphate free are safer for the environment and less likely to cause harm to plants.
9. Small Amount of Surfactants: Dish soaps are effective against certain garden pests because they contain surfactants that disrupt the pests’ cell membranes. However, too much surfactant can harm your plants. Ensure the soap you choose has a reasonable amount of surfactant for pest control without causing plant damage.

Consider using a pure-castile liquid soap. This type of soap is made from natural ingredients and is safe for plants.

Here are a few castile soap options you can use.

• Dr. Bronner’s – Pure-Castile Liquid Soap
• Adams Castile Liquid Soap
• Quinn’s Pure Castile Organic Liquid Soap

How to apply insecticidal soap on plants

To apply insecticidal soap on your plants, make sure you read and follow the label directions carefully.

Insecticidal soap works by suffocating small, soft-bodied insects and disrupting their cell membranes. It is important to apply the soap directly on the pests and to reapply regularly, as it only remains effective while wet.

Add the solution to a spray bottle and shake it well to mix all the materials.

Spray this solution on all the foliage where there are pests. Remember to spray underneath the leaves. Apply the solution on all the leaves where you see pests or damage because of pests.

It’s best to start with the weakest solution possible and only increase the soap concentration if it’s not working. Spray the solution until it drips.

Avoid spraying the solution when the sun is out because it can burn the leaves. The best time is early morning or late evening.

Do not use this spray on plants that may be stressed because of environmental stress such as transplant shock, lack of right temperature, or watering.

Don’t spray the soap if you see beneficial insects such as lady beetles or lacewings on the plant. Wait for a few hours and check again.

How often should you use insecticidal soap?

Insecticidal soap is milder than dish soap, but I would still only use it when necessary. I suggest using insecticidal soap as a treatment option only when you notice pests on the plants. Don’t use it as a method to prevent pests.

This way, you can minimize any potential negative effects on your plants while effectively controlling pests. Remember, moderation is key when using insecticidal soap as an insecticide.

How to make natural insecticidal soap

Here’s a simple recipe for making your own natural insecticidal soap that is cost-effective and natural. I would suggest making small batches and using the spray the same day for the best results.

1. Start with an oil base:

One cup of oil of your choice from below.

– Vegetable oil
– Peanut oil
– Corn oil
– Soybean oil

2. Add an organic, pure soap:

Use one tablespoon of organic castile soap (such as Dr. Bronner’s).

3. Mix these two ingredients thoroughly and add water:

Add two teaspoons of the mixture to every one cup of warm water.
Transfer the solution to a spray bottle.

Best insecticidal soap for plants

Choosing the best insecticidal soap for your plants involves considering several factors to ensure it effectively controls pests while minimizing harm to your plants and the environment. Here are some guidelines to help you make the right choice:

1. Read the Label:
   • Look for insecticidal soaps that are specifically labeled for use on the plants you have and the pests you want to control.
   • Check the label for any potential plant restrictions or sensitivity warnings.
2. Active Ingredients:
   • The active ingredients in insecticidal soaps are typically potassium salts of fatty acids. These are less harmful to the environment than chemical pesticides.
   • Ensure the product you choose contains a sufficient concentration of the active ingredient for effective pest control.
3. Targeted Pests:
   • Determine the pests you need to control. Different insecticidal soaps may be more effective against specific pests like aphids, mealybugs, whiteflies, and spider mites.
   • Some products may be labeled as “broad-spectrum,” meaning they target a wide range of common garden pests.
4. Residue and Toxicity:
   • Choose a soap with minimal residue and low toxicity to beneficial insects, such as ladybugs and bees.
   • Avoid using insecticidal soaps during the active foraging hours of pollinators to prevent unintended harm.
5. Mode of Application:
   • Check if the insecticidal soap comes in a ready-to-use spray or concentrate. Concentrates can be more cost-effective but require proper dilution.
   • Ensure it’s easy to apply and covers both the upper and lower surfaces of leaves where many pests live.
6. Safety Precautions:
   • Read and follow the manufacturer’s safety instructions, including recommendations for protective clothing, application methods, and any waiting periods before harvesting edible crops.
7. Compatibility:
   • Consider the compatibility of the insecticidal soap with other products you may use in your garden. Mixing certain products can be harmful to plants or reduce effectiveness.
8. Brand Reputation:
   • Research the manufacturer’s reputation for producing reliable and effective insecticidal soap products. Read customer reviews and ask for recommendations from local gardeners.
9. Environmental Impact:
   • Choose products labeled as “environmentally friendly” or “organic” if you are concerned about minimizing the impact on the environment.
10. Persistence:
    • Some insecticidal soaps break down quickly, while others may provide longer-lasting protection. Consider your specific needs and how often you’re willing to reapply the product.
11. Price:
    • Compare prices of different products and determine whether a higher-priced option offers better value in terms of effectiveness and quantity.
12. Storage and Shelf Life:
    • Consider the shelf life of the product and how it should be stored to maintain its efficacy.

Here are some good insecticidal soap you can use for your plants.

• Bonide Insecticidal Soap
• Garden Safe Insecticidal Soap
• Safer Insect Killing Soap Concentrate

Can you water plants with soapy water?

You should not water plants with soapy water because it will contain chemicals that damage plant roots and beneficial organisms in the soil.

Soapy water may contain chemicals such as chlorine or boron compounds that will be toxic to the plants. There may be a lot of salts in the soap, causing dehydration of the plants and organisms in the soil.

Will dish soap kill plant roots?

Dish soap will kill plant roots because it contains harsh chemicals such as chlorine, boron compounds, and salts. The chemicals can corrode or dehydrate roots and affect their water and nutrient intake.

The surfactants in dish soap can strip away the protective layer on the roots, making them more susceptible to drying out and nutrient deficiencies. The high pH levels in some dish soaps can alter the pH of the soil, further affecting the health of the roots.

Do you need to rinse off soap from plants?

Yes, you need to rinse off soap from plants because soap residue will block sunlight and hinder photosynthesis. It can attract dust particles and clog leaf pores, reducing transpiration. Soapy water can burn plants if you apply it under intense sunlight.