If you’ve ever dealt with pests in your garden, you’ve probably tried any number of supposedly effective home remedies that don’t actually work and just harm your plant, leaving the insects fat and happy. Or, you may have tried something more extreme by going down the route of toxic pesticides and been shocked to find out that these chemicals linger on your vegetables.
The good news is, there is an easy ready to use insect killer solution for soft-bodied insects that requires only two ingredients and is totally natural to help you deal with garden pests. Read on to find out more about insecticidal soap and how you can make your own garden pest soap solution.
What is Insecticidal Soap?
Insecticidal soap is a solution, either store bought or homemade, that is used to help eradicate small, soft-bodied pests such as aphids, whiteflies, spider mites, and mealybugs and keep them from eating or destroying your plants.
Aphid by Ryszard / CC BY-NC 2.0 Though aphids don’t look all that intimidating, they can quickly destroy your vegetables, flowers, and houseplants. Keep an eye out for these nasty pests and use insecticidal soap to eradicate them as soon as possible.
It works by penetrating the insect’s outer layer and drying them out, killing them and causing cell collapse. Other bugs may be suffocated by the spray, which could help eradicate some hard-shelled pests such as scale insects. Remember, beetles and caterpillars won’t be fazed by insecticidal soap so if you are experiencing issues with these chewing insects, you’ll want to consider other options.
Benefits of Insecticidal Soap
There are several benefits that come with using your own insecticidal soap products. You can start to experience these benefits as soon as you incorporate it into your garden or plant care routine. The biggest benefits include:
Unlike pesticides, insecticidal soap is totally safe and non-toxic, which makes it a desirable pest control option for many organic gardeners or for vegetable gardens where harmful chemicals could leach into your food. It is also a more gentle pest control option that will target the pests and leave your plant foliage untouched.
Not only does insecticidal soap work to get rid of a variety of insects, but it also works on pretty much any plant. Houseplant, fruit, vegetable, flower. You name it. Insecticidal soap is safe for a huge variety of garden dwellers and will also be one of the first things you reach for when you see those little spider mites taking up residence in your indoor palm.
June 2006 Garden 011 by speppers69 / CC BY-NC-ND 2.0 Palms are an incredibly popular houseplant but they are often subject to spider mites. Inspect your palm regularly and if you notice any white specks, webbing, or burning leaves, treat it with insecticidal soap immediately.
Considering that insecticidal soap uses a tiny amount of soap and water, you aren’t going to be paying much for it, no matter how many insects you need to kill. One bottle of soap could last you years, which makes this a totally economical and effective way to keep your plants pest-free and healthy.
Eco-Friendly Advantages of Insecticidal Soap
Homemade insecticidal soap is more eco-friendly than commercial-grade insecticidal soap, and this makes it much better for the environment. There are several advantages of using this soap, including:
- Biodegradable and nontoxic if you use the right soap
- Kills target insects without harming hard-bodied insects like predatory wasps, pollinating bees, and lacewings or birds
- No residual effect.
- Only works in direct contact with soft-bodied insects
If you’re not a fan of the DIY option and just want a quick, easy solution to your pest problem, Safer Brand Insect Killing Soap is a wonderful choice. It is safe, non-toxic and will kill aphids, earwigs, grasshoppers, harlequin bugs, leafhoppers, mealybugs, and mites and keep your plants safe. It will also work well on sawfly larvae, psyllids, soft scales, spider mites, blossom thrips, squash bugs, and whiteflies.
The main ingredients are potassium salts of fatty acids or potassium laurate. Fatty acid salts are found in most ready to use insecticidal soaps. It has no residential impact on the environment when you use it correctly. You can use this product up to the day of harvest without damaging your plants. It also works well for indoor gardening and hydroponic gardens.
Applying Your Insecticidal Soap
Just like anything you want to apply to plants, you want to read the label all of the way through and follow whatever directions it gives you. These soaps usually get used at a 1% or 2% solution at a rate of 2 ½ to 5 tablespoons per gallon. Always make a point to follow the label for the product you’re using, and don’t attempt to use it at a higher concentration because it can be harmful. Mix your soap concentrate in a clean spray bottle.
Don’t apply your soap when your plants are in the full sun, and the temperatures should be below 90°F to avoid damaging your plants. High humidity and temperature levels can increase your plant stress and sensitivity levels. You want to treat your plants either early in the morning or late during the day after dusk. The soap will only be effective as long as it’s wet, so these times will slow the drying conditions to allow for better pest control.
You want to spray both the top and the surface of your plants, concentrating on the bottom of the plants because this is where the bugs like to hide. The soaps also have a very short residual action and the insects have to come into contact with your soap for it to work. You will have to reapply it every four to seven days until your pests are gone. You should avoid excessive applications because it can cause leaf damage with repeated exposure to the soap.
Your water quality is another factor to consider when you use these soaps. Hard water will reduce how effective it is because magnesium, calcium, and iron can cause the fatty acid content to precipitate out of your soap. In turn, the soap will be largely ineffective. You want to use the purest water you possibly can when you create your soap to maximize how efficient it is.
You can find out if your tap water is compatible with yoru soap by mixing up the recommended concentration you want to use with the correct amount of water in a glass jar. Gently agitate the mixture and let it stand for 15 minutes. If the mix stays milky and uniform, your water quality will work with the spray. If you notice a scum forming on the surface of your spray after 15 minutes, you should use bottled or distilled water over your tap water.
There are a few disadvantages that come with using this soap, and they all revolve around how limited the soap’s nature is. The disadvantages include:
- No residual effectiveness when you use them because you wash it away or it dries.
- The soap has to be wet and hit directly on the insect for it to work when you apply it.
- If the soap residue gets impacted by high temperatures, there is a chance of phytotoxicity.
DIY Insecticidal Soap
This easy soap can be thrown together in just a few minutes and is a great, non-toxic option for keeping pests at bay. The soap itself is the active ingredient in your DIY insecticidal soap. While there is the possibility of the recipe wanting additional ingredients like cayenne or garlic, the soap is what is going to work to kill the bugs on your plants.
Ideally, you’ll pick out a soap that has no fragrance to it, and it shouldn’t contain specific added ingredients like bleach. Bleach and other additives can kill beneficial insects and desirable plants. The closer you manage to get your soap to be natural, the less likely it is to damage any beneficial bugs or plants around it.
What you need:
- Soap. While regular dishwashing soap will work in a pinch, the best soap to use as a natural insecticide is a pure soap with fatty acids that will work to eradicate bugs and will mix easily with water. Purse Castille soap is a great, inexpensive choice with these fatty acids. Make sure not to use product that has additives such as fragrance.
- Water. Tap water should get the job done but if you have hard water that is loaded with hard mineral deposits, you may want to use distilled water or bottled water instead so you can kill insects without harming your plants with soap scum buildup due to the hard water.
- Soap Spray bottle. Your bottle size will vary depending on what you need your insecticidal soap spray for. If you have a few plants with pest problems then you will want to make a decent amount, but otherwise, one medium-size soap spray bottle should be enough. You can easily put together another batch of insecticidal soaps if you need to.
What to do:
- Step 1: For a one-quart spray bottle, simply fill it up with warm water.
- Step 2: Add 1 tablespoon of insecticidal soaps. (This amount will need to be adjusted depending on the size of the batch but a good measurement to go off of is 1 tablespoon of insecticidal soaps for every quart of water)
- Step 3: Screw on the lid and shake to mix well.
While the above recipe is certainly effective and will eradicate most soft-bodied pests, many gardeners find that adding a little something extra can be helpful in dealing with particularly nasty infestations. Here are a few ingredients you can add to your insecticidal spray if you need to increase its potency:
- 1 tsp garlic or 1 tsp crushed red pepper per gallon of water (helps repel chewing insects because of the pungent flavor)
- 1 tsp apple cider vinegar per gallon of water (helps with powdery mildew)
- 2 Tbsp vegetable oil (helps the spray stick longer)
Olive Oil by Prem Sichanugrist / CC BY 2.0 Olive oil or vegetable oil can be added to your soap to help increase its effectiveness and help it stick to the leaves. Vegetable oil is often cheaper than olive oil and is just useful so it may be the better choice.
Many gardeners also make insecticidal soap by combining one cup of vegetable or olive oil with one tablespoon of soap and then mixing two teaspoons of this soap and oil concoction into one cup of warm water. Try both methods to see which works best for you.
How Do You Use It?
Like carpet cleaner, you always want to test a patch before you spray insecticidal soap over your entire garden. Who knows, you may have made the solution too strong, or your plants could react badly to it. In any case, spray it on a few leaves and let it sit for at least 24 hours. If it hasn’t damaged the leaves at all, (look for browning, wilting, spots, or wrinkling) you are cleared to continue using it.
Remember, you should never use insecticidal soap on stressed out, wilted, or newly transplanted plants as it could prevent them from recovering.
Always shake the bottle well before using your spray, as the soap and water may have naturally separated. Cover the entire affected plant in a generous coating of insecticidal spray, getting the undersides of the leaves as well as the top soaked in soapy water. Be sure that you aren’t using it on a rainy day as it could just wash right off before it has a chance to work. However, it is also important that you don’t do it at a time when the sun is beating down on your plant as it could lead to burning and sun damage. Stick to an early morning or evening application.
Unfortunately, insecticidal soap is not a magic solution that will immediately get rid of all your pest problems. Check your plant about a week after application and reapply if needed. Continue weekly reapplication until the pests are gone.
Caution of Using Any Insecticidal Soap
When you use this soap, you have to be careful as to which plants you use it on because some are far more sensitive than others. Putting your soap on these plants can lead to damage, and you want to avoid:
- Bleeding heart (Lamprocapnos spectabilis)
- Cherries (Prunus spp.)
- Crown of Thorns (Euphorbia milii)
- Easter lilies (Lilium longiflorum)
- Gardenias (Gardenia jasminoides)
- Hawthorn (Crataegus spp.)
- Horse chestnut (Aesculus hippocastanum)
- Japanese maple (Acer palmatum),
- Lantana (Lantana camara)
- Maidenhair fern (Adiantum spp.)
- Mountain ash (Sorbus spp.)
- Nasturtiums (Tropaeolum spp.)
- Plum (Prunus spp.)
- Portulaca (Portulaca grandiflora)
- Sweet pea (Lathyrus odoratus)
Under drought conditions, conifers can be sensitive to soap, even DIY mixtures. Plants that have a bluish tint to them that comes from waxy leaf coatings can lose their color as the soap strips the wax away. There are plants that are less sensitive to soap, but it can still cause problems, and they include:
- Azaleas (Rhododendron spp.)
- Begonias (Begonia spp.)
- Fuchsias (Fuchsia spp.)
- Geraniums (Pelargonium spp.)
- Impatiens (Impatiens spp.)
Rinse your plants with a clean water spray if you see any signs of leaf edge browning or wilting in a few hours after you spray them. You can easily test for plant sensitivity if you’re not 100% sure by spraying a small area and wait 24 hours to see if any damage manifests. Don’t spray plants under stressful conditions.
Limitations of Insecticidal Soap
Once this soap dries, it won’t have any more activity. So, the spray has to be wet and touch the insects or it won’t work. Insects won’t die from this spray just from eating plant tissue that has been sprayed with soap or from walking across it. You have to thoroughly cover all of your plant foliage with your spray for the best results. Not all plants will appreciate a bath in this soap.
Even more gentle soap can cause your plants to surfer from phytotoxicity, including white gardenias and New Guinea impatiens. Both of these plants grow in planting zones 10 through 12, so they have a slightly more restricted area to grow in.
Symptoms of phytotoxicity include scorched leaf tips, burned foliage, and yellow or brown spots that develop on the plant’s leaves. You can reduce the risk of plant damage by making sure that your plant’s solution isn’t more than 2% or 3% strength. You should also make a point to get your hose and water down your foliage two hours before you apply your soap to give it an extra layer of protection.
Leaf footed by family by Jean and Fred / CC BY 2.0 Insecticidal soap isn’t an end all solution for your bug problem, and you’ll have to work on reapplying it to protect your plants. More severe infestations will require a heavier dose of spray and more treatments to work.
Tips To Apply Insecticidal Soap
There are several things you can do when you want to apply your insecticidal soap to make it more effective and maximize how well it works for you. They include but are not limited to:
- Test your soap solution rate before you spray
- Don’t spray on rainy days and double-check the weather before you spray
- Spray before 9:00 am or after 5:00 pm to allow the spray material to be more effective and stay wet longer on your plant
- Keep the solution agitated and mixed by shaking well before you spray it. Keep shaking it as needed, and shake it before you spray if you had it sit for a few days previously
- The spray isn’t residual, and you want to remember this as you spray it. The soap spray has to cover and get the pests wet for it to work, so don’t just spray the foliage.
- Take time to cover the underside and tops of the leaves and stem each time you spray it.
- Give mites, mealybugs, or aphids a good coating of the spray each time you use it.
- Apply the spray to well-watered and healthy plants. Don’t spray on wilted plants.
- Avoid applying your soap to tender growth, sensitive plants, or blooming plants to avoid scorching or other problems.
- Repeat your spray application at least once a week. A lot of pests require follow-up sprays to get rid of them, depending on how severely infested your garden is.
- Pick out fragrance-free soap and a soap that doesn’t have additives like bleach because this can kill off insects and desirable plants. The more natural your soap is, the less harsh it’ll be on the surrounding environment.
- If you leave your spray sitting on a shelf without using it for 30 days or more, double-check that it is still viable. The oil in the mix can go bad, and this can make your spray look slightly cloudy or have a nasty smell to it. The best thing you can do is mix up a fresh batch if you think it isn’t viable anymore.
How to Store Homemade Insecticidal Soap
If you mix up too much soap to use in one go, you may have to store it until you need to treat it again. You should sit this soap on a shelf in a cool, dry space. Always shake it well before you use it and check to see if it went bad. If so, you’ll have to discard it and make a new batch.
Insecticidal Soap Frequently Asked Questions
Keeping your fruits, flowers, vegetables, or other plants healthy requires you to routinely inspect them for insect infestations or diseases. If you don’t treat them quickly, the pests can ruin your harvest or strip the blooms right off your plant. Applying insecticidal soap will form a protective barrier on your plants while killing the pests. For anyone who wants to make their own soap and haven’t ever done so before, questions are common.
1. Can I make my own insecticidal soap?
Yes, you can make your own insecticidal soap for your plants. All you have to do is mix 2.5 tablespoons of vegetable oil with 2.5 tablespoons of pure liquid soap with a gallon of distilled water. This will give you a full gallon of soap to spray in your garden or on your plants.
2. Will Dawn dish soap hurt plants?
A lot of people can successfully use Dawn as the liquid soap in their soap solution. But, you have to note that Dawn has a host of artificial ingredients and colors in the formula, unlike Castile. These things might not hurt your plants, but picking out a soap that doesn’t have artificial ingredients or fragrances is a much more eco-friendly choice.
3. What is the best insecticidal soap?
Both commercial and insecticidal soaps can be beneficial for your plants. If you want to buy a ready-made mixture that is safe to use on a range of plants, make sure that it has an OMRI (Organic Materials Review Institute) certification on it. This is safe for use on all plants, and this includes vegetables.
4. Can insecticidal soap kill plants?
If you use a percentage of soap that is too high for your solution, you run the risk of harming your plants. It also increases if your liquid soap in your recipe has other ingredients or chemicals in it. For the safest and best results, stick to using a natural liquid soap and stick to the recommended ratios.
5. How often should I spray my plants?
For typical protection against insects, make a point to spray your plants once a week. If it rains heavily, you’ll have to reapply it sooner.
6. What is the best natural insecticide?
There are several natural insecticides available that are safe and effective to use on plants. Solutions include diatomaceous earth and neem oil. However, they’re not found in these soap mixtures because insecticidal soaps have oil, liquid soap, and water in the solution.
Now that you know how to make your own insecticidal soap, you can mix up a batch for your plants. We’ve told you some do’s, don’ts, and a few tips to ensure that they work well without taking over the space. You can try them out and see which ones work best for your needs this season to protect your plants.
Jen is a master gardener, interior designer and home improvement expert. She has completed many home improvement, decor and remodeling projects with her family over the past 10 years on their 4,500 sf Victorian house. She is also a passionate farmer who keeps goats, chickens, turkeys cows and pigs on her farm, and an instructor for her community’s Organic and Sustainable Farming project.