Does Dish Soap Kill Lawn Pests, and Is it Safe?

Lawn Care Tips

Dish soaps have long been used to kill insects in lawns. But are they really effective at eliminating plant-eating pests, and do they harm your plants? Let’s explore if dish soap kills lawn pests and if it’s actually safe to use.

In this article:

Does dish detergent kill lawn pests?

The short answer is yes, dish soap is an effective and increasingly popular way to exterminate grubs, sod webworms, cutworms, and other soft-bodied insects. Dish detergents disrupt the cell membrane of these soft, small insects and smother them to death. Grubs drown in dish soap and are suffocated by the fluid coating them. 

Dish soap has been shown to kill other lawn insects as well, and even dries out and kills fungus in lawns. 

Some other common garden pests that a dish soap kills include:

  • Fleas
  • Grasshoppers
  • Aphids
  • Japanese beetles
  • Leaf hoppers
  • Planthoppers
  • Harlequin bugs
  • Whiteflies
  • Grubs 
  • Thrips
  • Spider mites
  • Scale insects
  • Ants

How does it work?

Dish soaps, which are actually detergents, have been used to control lawn pests for many years, but their efficacy as a pesticide has only recently been scientifically established. How these dish-cleaning products kill insects is, however, still poorly understood on many fronts. 

Dish soaps are usually applied to plants and grass diluted with water, typically in around 2-3 percent concentration. Experts recommend mixing a bit of vegetable oil with household liquid dish soap and water in a bottle and spraying it directly onto the affected areas of your lawn, then letting it soak in. Finally, you should rinse it off with a hose after an hour or so.

Researchers have found that some soaps dissolve only the outer waxy coating of an insect’s exoskeleton or cuticle, which destroys its watertight quality. Removal of these protective waxes from their bodies causes excess loss of water and results in severe dehydration and eventually death. Soft-bodied, small insects are especially susceptible to the effects of dish soap. 

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Some commercially available soaps come with insecticidal properties that mainly target and affect the nervous system. Such soaps are apparently only effective against plant-eating insects and have a toxic effect on them. This means that they might spare beneficial insects such as lacewings, ladybird beetles (ladybugs), and predatory mites. 

Then there are some high-pressure sprays that wash off insects from the plants after the soapy water immobilizes them. Soap solutions will work on most ornamentals, houseplants, and fruit trees. 

Is dish soap safe for plants and lawns?

Dish soap isn’t selective about removing oils and drying out cell membranes. It will dehydrate and kill the grass just as it would the nasty pests in your garden. So, yes, dish soap is not an entirely safe way to remove insects and lawn pests. 

With that said, soaps won’t always kill your lawn altogether. The damage a dish soap or detergent might do to your grass depends mainly on its chemical constitution. Dish detergents contain synthetic chemicals, called surfactants, that are designed to break down organic matter in food, while dish soap is composed of natural fats and oils. 

Dish soaps contain sodium lauryl sulphate or either sodium hydroxide or potassium hydroxide as its primary active ingredient. Sodium lauryl sulphate is an extremely potent chemical that breaks down oils to clean your dishes. It does the same to any surface it comes into direct contact with, including your plants and grass. 

But there are a few hacks that lessen the impact of dish soaps and detergents and allow you to use them safely as an insecticide. You’ll simply need to create a very diluted mixture of dish soap, water, and vegetable oil and then hose it all off within an hour of application to keep your lawn grass healthy. 

How should you apply it?

For dish soap to work as a pesticide on your lawn, it needs to come into direct contact with the fungus, moss, bugs, or insects causing the problem. Here are some simple steps to follow for a safe application:

  • Check the weather forecast for the day you’re planning to do the deed. Rain will wash away the spray, so, any treatment should be applied when there’s no rain.
  • To prepare the potion, combine a teaspoon of liquid dish soap, a teaspoon of vegetable oil, and a cup of water in a spray bottle and mix thoroughly.
  • Spray the affected plants early in the morning or early in the evening, when the temperature isn’t too high. When it’s too hot outside, the sun will dry out the spray quickly and will burn the grass. If you’re treating an indoor plant or plants that are mostly shaded from direct sunlight, you may apply the spray at any time of the day.
  • Test the spray on a small area of your lawn to make sure it isn’t too harsh. If your lawn shows no signs of distress, go ahead and spray it on all the affected areas of your garden or lawn.
  • When applying, remember that your soapy water mixture should not only directly touch the insect but it should essentially coat its body to work properly. If you’re applying it on a plant, make sure you spray the undersides of leaves and the stem too.
  • If possible, use a high-pressure spray that gives you physical and chemical pest control in one application. High-pressure sprayer will knock the insects off the plant and grass leaves.
  • An hour after applying, rinse the mixture from your lawn with a hose.
  • Repeat the process for a few days if the pest problem persists.

Alternatives 

There are a few other concoctions that work for lawn pests and are also safer than using harsh detergents. The safest way is to purchase soaps that are specifically formulated for use on plant and lawn insects. They don’t contain synthetic substances and won’t damage the grass. A few options include:

  • Insecticidal soaps: These are formulated as pesticides and are safe for use in lawns and gardens. Insecticidal soaps work like dish soaps but are manufactured using a combination of potassium hydroxide and sodium hydroxide with fats. 

They create sodium or potassium salt of fatty acids that kill a variety of pests and are designed to be gentle on plants and grasses. But even though they’re less hazardous to plants, you should never overdo them.

  • Low-toxic pesticide soaps: If your lawn is infested with delicate insects such as whiteflies, spider mites, and aphids, low-toxic pesticides are your best bet. These solutions target the waxy exterior of insects and kill them. 

Also, they won’t hurt beneficial insects such as ladybugs and honeybees or animals as they’re designed to only attack insects with wax skins. In fact, they will wash off any mold or honeydew sap – the two bane of a lawn’s existence. 

  • Organic pesticides: There are many organic insecticides available in the market today, for example, neem oil. Organic products are the safest alternative to dishwashing soaps and detergents used for pest control. Check out other options for organic pest control at Lawn Love. 

Frequently asked questions:

Q. What are some of the benefits of using dish soap to eliminate lawn pests?

A. Dish soap is safe for humans, easy to apply and effective on a range of lawn and garden pests.

Q. What are some of the limitations of using dish soap on lawn pests?

A. Dish soap can be less effective than commercially available pesticides because it must come into direct contact with the insect to be effective, and its effects are short-lived. It is most effective for targeted treatments.

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