Dish Soap like Sunlight or Dawn is a regular addition to home pest control remedies for the garden. You use dish soap every day and eat from the dishes you clean with it – how can it be harmful to plants? It’s time to look through the bubbles and see the truth.
Dish Soap – What is It?
Dish soap is a generic term, but it usually refers to the liquid soap products used for washing dishes. Dawn, Joy, Palmolive and Sunlight are very common brand names. It also goes by the names Dish washing liquid, washing-up liquid, dish washing soap, and dishwasher detergent.
Dish washing soap is a detergent that can include phosphate, bleach, enzymes, dyes, fragrances and rinsing aids.
Scientists distinguish between soap and detergents which, chemically, are quite different. Soaps are cleaning agents made from natural oils and fats. Detergents are cleaning agents made from synthetic chemicals called surfactants. Soap and detergents both clean, but the chemicals in the products are different.
Dish Soap is actually misnamed. It should be called Dish Detergent. You will see why this is important in a few minutes.
Dish soap works by dissolving greasy chemicals like oils, fats and waxes and it is excellent at this job. It is also a powerful degreaser.
Insecticidal Soaps – What Are They?
Insecticidal soaps are pesticides that are used in the garden. I’ll talk more about how and why to use them below.
Insecticidal soap is a true soap, not a detergent.
A soap is made by mixing together sodium hydroxide, or potassium hydroxide with fats. The final product is something called either sodium salt of fatty acid, or potassium salt of fatty acid. This is the same ingredient found in most bars of soap, and in liquid hand soap. Chemically these are very different from detergents, although both clean things.
Insecticidal soap is a special kind of soap. It is made using only potassium which produces a milder, softer soap than sodium. It also uses long chain fatty acids – a special type of fat. This soap is specially made to be mild on plants.
Soaps will also dissolve greasy chemicals like oil, fat and wax, but they are not as good at this job as detergents. From a cleaning perspective insecticidal soap is a great soap.
Dish Soap On Plants
What happens when you spray diluted dish soap on plants? Remember dish soap is a detergent that is excellent at removing oil, grease, and wax. When you spray it on your plants, it removes the natural oils and waxes that all plants have on their leaves. These oils and waxes serve to protect the leaves.
When the protective coating is removed from the leaves, it makes it easier for pathogens to get a foothold and infect the plants.
Spraying your plants with dish soap removes their natural defenses against pests and diseases. You are setting the stage for your plants to get sick, and maybe die.
DIY Insecticidal Soap
There are many DIY home recipes for making insecticidal soap. The problem is that NONE of them are insecticidal soap. If they use dish soap – they are detergents, not soaps. If they use liquid hand soap, the fatty acid salts are made from short chain fatty acids which are phytotoxic to plants – they damage plants. You can’t make insecticidal soap using things you find around the house.
One recipe on the internet says “Use a pure liquid soap… Don’t use detergents, dish soaps, or any products with degreasers, skin moisturizers, or synthetic chemicals. ” Soap is a synthetic chemical!
Will the homemade insecticidal soaps get rid of insects? Maybe, but they will also damage and weaken plants.
Is Dr. Bronner’s Castile Soaps Safe?
Castile soaps, of which Dr. Bronner’s is a popular brand, are made from vegetable oils (particularly olive, palm, and coconut) using potassium hydroxide. So they are potassium based soaps and therefore many people claim that they are the same as insecticidal soap. Most castile soaps are mixed with fragrances and essential oils for a wide range of uses but not as insecticides. This soap maybe safer than other sodium-based soap, but nobody really knows what the additives will do to plants. Since it is not labeled as a pesticide it should not be used.
Use Insecticidal Soaps Correctly
My post, Insecticidal Soap – Use it Correctly, provides more detailed information on how to use these products. In summary, they are only effective if you spray the insects – not the plants. Insecticidal soaps are much less harmful to plants, but even they should not be used to cover the whole plant. Although, fairly safe for plants, they will harm certain plants – look at the instructions an keep away from sensitive plants.
Hello Good Morning Robert ! Yesterday I sprayed a gone remedy of baking soda / dish soap and vinegar this morning I realised my misfortune and flushed the plants with water and i was told to rinse with dish soap / liquid soap which i did ! Will my plants survive ? The stems are still green and I cut back the burnt leaves .
no way for me to tell.
Hey I sprayed off what I put on my leaves that are wilting….will they recover?
I am in the same boat, my beautiful garden was getting eaten up by caterpillars so I did the dawn thing and they look dead. I haven’t seen any response to those questions. What can I do now? please help
Wait, and stop spraying stuff.
Hey! So I’m pretty sure my plants are being eaten by thrips and I was using insecticidal soap and it wasnt getting any better so I tried the dish soap mixture since it said it was safe (first time planter here) and now my leaves are yellowing. How do I get these thrips away while also not harming my plants!?
Hello! I have been using potassium soap to spray my infestation of halticini bugs that I can’t get rid of in my green house,.. it does kill them but leaves a soap taste on my food even after washing,.. and I have to be constantly spraying to keep the infestation from decimating everything,… these bugs are terrible! Since I live in a tropical climate there is no freeze to help. I’ve tried diatomáceos earth(did practically nothing), Bavaria fungus(too hot here for that to work I think) yellow sticky pads(help but not enough). … any suggestions?
I am raising milkweed for Monarch caterpillars’ food source as well as the butterflies eat the milkweed flower nectar. Will insecticidal soup harm the caterpillars and butterflies?
Probably. It is an insecticide – it does not know bad bugs from good.
Thank you Robert. We’ve heard that mixing Dawn, castor oil and water makes a great natural mole repellant for our lawn. Our question is, while it may get rid of the mole issue, is it safe for our lawn?
How are you defining “safe”? I would not put motor oil on my soil.
To make a neem oil spray, you need to mix it with some form of liquid soap to emulsify it or it separates from the water. They always say to use a mild liquid soap. Would it be best to use an insecticidal soap for this? Thank you!
yes
Hi Robert, thank you for your article and helpful insight. I’m having a cricket problem in my garden and looking for safe ways to free my garden of them. I haven’t done anything yet and have found a lot of contradictory information regarding how to get rid of them. It seems they are field crickets, but have also made mole holes in my grass and gardens. Any advice you have is very much appreciated, thank you! – Christina
Hi, I have ants that have made themselves very much at home in some of my indoor pot plants – ceropegia woodii/variegata, ctenanthe pilosa & stromanthe tricolour – how do I get rid of them without harming my plants? I haven’t had any success finding insecticidal soap, & I have been told to put them in a bucket of water with dish detergent, but they’re already sensitive enough plants, I don’t want to damage them!
Try putting some borax and sugar outside the pots where the ants will find it. It should kill them.
https://www.gardenmyths.com/get-rid-ants-naturally/
Hey hru? Ok so I have been growing zucchini and crooked neck squash green been etc. well I had i a huge ant break out in my squash only to find there were also these yellow little bugs eating my cantaloupe and squash well they still looked beautiful but the leaves were turning yellow and so I mixed neem oil and Palmolive dish soap this time never had a problem with neem oil before but read you could mix the 2 for heavy infestation I did. The first day after they looked great then the next day after I notice all my squash leaves were browned along with other plants. Some not but the leaves were just falling off. Sorry so long but I don’t want to lose all my hard work. Will they die off? Should cut my losses and start over just in case they don’t recover?
New shoots should sprout.