When the planting season gets going, the one thing you don't want to think about is those pesky pests and aphids munching on your precious greens. Aphids and other soft-bodied insects can affect the health of any plant by eating the leaves, fruit or stalk.
Once you have a plant that becomes active with pests, you are going to want to get it under control with a safe method that will not harm your plant or any of the beneficial insects that you may want to welcome to your garden or backyard.
You can easily get rid of aphids, spider mites and other insects destroying your plants with insecticidal soaps, but it is very important to understand the soap you are putting into your DIY insecticidal soap recipe, as some may be harmful to your plants.
We are going to share an easy DIY insecticidal soap recipe that you can whip up anytime to save your plants from bugs who are eating them before you do, and we will also share the difference between homemade insecticidal soap and store-bought insecticidal soaps to help you decide which is the better option for your plants.
How To Make Insecticidal Soap
Insecticidal soap has long been used on plants and flowers to try and save them from aphid and other pest infestations. Insecticidal soaps can be made, or they can easily be can purchased online and delivered to your door in their own handy spray bottles. It is up to you which method is more convenient or cost-effective.
It is also important to know what the actual difference is between store-bought insecticidal soaps and the homemade version, as well as which soap you should and shouldn't use in your DIY recipe.
We will talk about all of these important points in this article.
What Is Insecticidal Soap?
Insecticidal soap, often called horticultural soap, is a safe and environmentally-friendly bug spray that does not have harsh pesticides in it.
Insecticidal soap will not harm your plants and does not affect the food or flower that the plant produces as long as it is used according to the directions on the bottle for how much and how often your plant should be sprayed as treatment.
The same principles can be applied to your homemade insecticidal soap so long as you make it using the correct soap and soap to water ratio.
What is nice is that the horticultural soap won't harm your pollinators, so long as you don't directly spray them when they are there.
Insecticidal soap is a preferred method of pest control by natural and organic gardeners. It is easy to make or purchase and it is easy to use.
How Does Insecticidal Soap Work?
It is assumed that insecticidal soaps work by adhering to the bodies of soft bodied insects such as aphids, spider mites and mealybugs.
It is believed that the soap spray penetrates their fragile skin by affecting the waxy coating of it, causing cellular breakdown. The bugs eventually die and fall off of the plant host.
Insecticidal Soap Research
According to Scott Oneto, the Farm Advisor at the University of California Cooperative Extension, it is actually not extensively understood exactly how soap sprays kill plant-eating pests:
Researchers have been studying how soaps work in combating pests. Some soaps simply wash off the outer waxy coating of the insect's cuticle, destroying its watertight quality and causing the insect to dry up and die.
Other soaps have additional insecticidal properties that may affect the nervous system. These soaps appear to have toxic effect only against plant-eating insects and thus may spare beneficial insects such as ladybird beetles (ladybugs), lacewings, and predatory mites.
This is why your soap spray won't affect your local bees or pollinators; they are not plant-eating insects.
The Difference Between Homemade And Store-Bought Insecticidal Soap
There is a difference between homemade insecticidal soap and store bought horticultural soap, and that difference lies in the soap ingredient.
According to a paper about managing pests with soaps from the Institute of Food and Agricultural Sciences at the University of Florida:
[Store bought] Insecticidal soap products typically contain potassium salts of fatty acids. The fatty acids are naturally found in fats and oils of animals (e.g., lard, fish oil) and plants (e.g., cottonseed, olive, palm, coconut oils).
Most modern soaps are produced using sodium hydroxide, a very efficient modern lye. However, insecticidal soaps are made by saponification with potassium hydroxide, a traditional lye.
The traditional lye is made using the fatty acids found in oils from animals and/or plants. When you make homemade insecticidal soap, you are adding a dish soap which does not have the fatty acids that pure liquid soap has, and it is not intended for pesticidal use.
These dish soaps are made with modern lye from sodium hydroxide, and they may unintentionally take the waxy surface off of your plants. Even a mild liquid soap or dishwashing detergent may do this as well if you spray plants with it.
Dish Soap Vs. Soap Found In Insecticidal Soap
Why is it important to use an insecticidal soap where the soap's saponification process is made with potassium hydroxide as opposed to dish soap whose saponification is made through sodium hydroxide?
The study above continues:
While soaps produced by either process will kill soft-bodied organisms, the sodium found in modern soaps is toxic to plants, and excessive use can leave a damaging amount of sodium ions (negatively charged molecules that can dry out plant tissue) on the plant surface.
When making your own insecticidal soap, you need to use a soap whose saponification process is made through potassium hydroxide (the traditional way).
Which Soap To Use In Your Recipe
You can do your research into the saponification chemicals used in your dish soap to make sure you find one that uses potassium hydroxide; however, many companies don't list this as an ingredient because it is not actually an ingredient; it is an activator and the end product does not contain potassium hydroxide (therefore, it is not an "ingredient").
The same goes for looking for sodium hydroxide in the ingredient list.
So which liquid soap should you use in homemade insecticidal spray?
Dr. Bronner's pure castile liquid soap is our recommendation for any DIY insecticidal soap recipe. It uses the same saponification catalyst as insecticidal soaps (potassium hydroxide), as opposed to sodium hydroxide, which can damage your plant with the sodium concentrate.
You can clearly read this right in their liquid castile soap ingredient list which we are lucky that they shared this information with consumers.
Homemade Insecticidal Soap
If you want to try making your own DIY insecticidal soap, here is a recipe we use. This recipe works well around our gardens.
Insecticidal Soap Ingredients:
- 5 Tbsp Dr. Bronner's Liquid Castile Soap in unscented (or another liquid soap that uses potassium hydroxide for their saponification process as opposed to sodium hydroxide)
- 1 gallon of tap water, bottled water or distilled water
- A clean spray bottle. These are easily found at your local dollar store or on Amazon
Other recipes will often include ingredients such as apple cider vinegar or ground red pepper to help kill the insects, but we don't use those ingredients as they may affect the plant tissue, especially if your plants are located in hot, sunny areas.
There are other recipes out there as well that call for natural oil, vegetable oil or olive oil to be added to your insecticidal soap recipe as well, but we ask, why would we add an oil to a formula that is made to eliminate oil? Sometimes, you've just got to keep it simple.
Insecticidal Soap Recipe Concentration
The concentration of 5 tbsp of Dr. Bronner's liquid soap to 1 gallon of tap water works out to a 2% soap concentration.
We recommend spraying a test area on one of your plants and checking it after 24 hours to make sure it will be alright on your plant.
If your plant reacts to it, the soap concentration may be too strong and there may be too much soap in your solution. You can further dilute the soap from 5 tbsp to 2.5 tbsp to bring your solution to a 1% soap concentration, and try it again.
This may be especially important if you are using it on delicate plants such as sweet pea or inpatients.
When spraying plants to treat the bugs on it, try to directly spray the insects and not the fruit or their flowers or edible plants. This is how the soap works to treat the problem; it must make contact with the bugs to work effectively.
This is why insecticidal soap is a treatment of pests and not a preventative measure. You can't preemptively spray your plants before the bugs get there; it will not do anything to them or deter them.
Insecticidal Soap Making Directions:
1. Mix your liquid soap and water together
2. Pour your homemade insecticidal soap into your clean spray bottle
3. Test 1 plant that is affected by pests. Do not spray any fruit or food directly, this spray is to be used directly on pests on the leaves, vine and stem of your plants
4. Wait and watch your test plant for 24 hours. If everything looks good, spray your other plants that have pests on them
5. Repeat insecticidal spraying if necessary up to one time per infestation. If you are repeating a third time or more, lightly rinse off your plants with a clean, water-filled spray bottle or a hose on mist setting and let it dry before spraying again
Apply insecticidal soap to plants that have an infestation of aphids or spider mites to kill and get rid of them.
If you are making your own DIY recipe, it is best to make it as needed. Simply bookmark this page and come back when you need to make a new batch.
Remember, insecticidal soap is not a preventative formula; but rather a solution to an already existing problem. Use it to treat plants that have a current pest problem.
Plant Health And Insecticidal Soaps
It is best practice when applying insecticidal soap spray, to use it on healthy plants and plants that can tolerate it. If you have wilted plants or susceptible plants that are prone to damage if they get directly wet, then you may want to make sure your plant is at optimal health and can take the spraying.
Certain plants, especially in the squash family (zucchini, butternut squash, pumpkins) can develop what is called powdery mildew if directly watered from above too often. So just be aware of how often you are spraying and try to avoid areas that are not infested.
Your goal is to directly spray the bugs.
Which Plants Should Not Be Sprayed With Insecticidal Soap
There are plants that are fragile enough that this gentle recipe would be hard on. Here are some plants that may not tolerate insecticidal soap well:
- Sweet peas
- Newly planted plants that may be going through a shock already
- Plants that have not matured yet (plant starts)
Using Insecticidal Soap Indoors
You can also use insecticidal soap for spraying indoor plants as well if you have a bug problem. If your plants are inside a house you can use insecticidal soap the same way as you would for outdoor garden pests.
Other Natural Insecticides
There are also other things you can do when it comes to natural insecticides. Have you ever heard of purchasing and releasing ladybugs, who are insects that eat aphids?
You can purchase ladybugs online and have them shipped to your door and release them where you are having an infestation.
What the ladybugs will do, is eat the aphids and other pests that are on your plants, and it is another option you can feel good about if you want to be as environmentally conscious as possible.
You can also release ladybugs right in your outdoor garden and they will feast away on those pests.
Don't worry if your garden that is affected by pests is in a greenhouse or is located outdoors. The ladybugs will certainly stick around to eat the bugs, but will fly off afterwards once the problem is essentially taken care of.
If you are releasing in a greenhouse, you can leave your doors open once you feel the pests are taken care of and the ladybugs will fly off to search for more insects to eat. You can treat any leftover pests with your insecticidal soap!
The Best Insecticidal Soap
If you are looking to purchase insecticidal soap instead of making it, there are some really great brands out there that are extremally effective, have a long shelf life and are free from toxic pesticides and harmful chemicals. Some of them even repel chewing insects in their spray material.
We highly recommend Bonide's insecticidal Soap, and you can check that one out on Amazon right here.
How to Store Homemade Insecticide Soap
When making your own recipe, it is always best to make a batch of horticultural soap, use it on your plant pests, and discard any leftovers. When you need to use it again, make a fresh batch.
If you do want to store the batch you made though, try keeping it in a clean, sealed container. You will need to shake it up again before using. It does not need to be kept in the fridge, but I wouldn't recommend keeping it more than a month.
If you need to use your insecticidal soap recipe again, you will want it to be as potent as the day you first made it for efficacy reasons.
Insecticidal Soap Summary:
- Insecticidal soap spray works by penetrates the fragile skin of pests by affecting the waxy coating of it, causing cellular breakdown.
- It is a treatment for aphids, spider mites and other plant pests; not a preventative treatment to be left on plants
- Insecticidal soap will not harm other insects that are beneficial to your plants
- When making your own homemade insecticidal soap, you NEED to use a soap whose saponification process uses potassium hydroxide as opposed to sodium hydroxide (used in most dish soaps)
- While soaps produced by either process will kill soft-bodied organisms, the sodium found in modern soaps (with sodium hydroxide) is toxic to plants (use the soap we recommend above in the article for your DIY recipe)
- It is best to make a fresh batch whenever you need your insecticidal soap, however, it can be stored in a sealed container
Here are some other questions that people are asking about making your own insecticidal soap.
What does insecticidal soap do to plant-friendly bugs?
If you are worried about the bees, worms and other plant-friendly bugs, worry not my friend. Insecticidal soap kills bugs on contact, and if you are purchasing insecticidal soap that is made for pesticidal purposes, it will only affect plant-eating bugs.
Do you need to rinse off insecticidal soap?
Insecticidal soap can be used without rinsing once or maybe twice if you are spritzing your plant. If you find you are reaching for that homemade insecticidal soap more often, you will want to reach for the hose (on a very gentle, mist setting) or even a new spray bottle with water and give your plants a little water bath once the spray mix has done its job. This will avoid a soapy build-up on your plants.
Can insecticidal soap kill plants?
If making your own insecticidal soap with Dr. Bronner's pure liquid castile soap, it is important to know that soap has not been registered for pesticide use, although it does state on their website that it can be use for insecticidal purposes. It is not a guarantee that it will not harm your plants (but with our experience it has been fine).
Store-bought insecticidal soaps are made with the intent of being sprayed on plants, so that may be a safer option. I will say that I have never lost a plant using a homemade insecticidal soap, yet the risk is up to you.
It is always important to always do a test area on your plants first, and be sure to spray the bugs directly and try your best to avoid flowers, fruit or leaves of plants if you can.
What is the best liquid soap for DIY insecticidal soaps?
Most modern soaps are made using sodium hydroxide, but insecticidal soaps are made with potassium hydroxide, a traditional lye. When you make homemade insecticidal soap, you are adding a dish soap which is not intended for pesticidal use which are made with the modern lye of sodium hydroxide.
We like Dr. Bronner's pure castile liquid soap because they use potassium hydroxide to saponify their soap (the same as insecticidal soap recipes) as opposed to using sodium hydroxide. Potassium hydroxide have those same potassium salts of fatty acids that affect the pests on your plants.
Can I use insecticide soap in my vegetable garden?
You can use insecticidal soaps in a vegetable garden. It is a safe alternative to the harmful chemicals found in pest control products. Insecticidal soap works very well at keeping insect pests in your vegetable patch under control. Make a fresh batch each time you need it if you are making it yourself.
Well we hope you found our post for homemade insecticidal spray enlightening! Please be sure to bookmark this post or save a Pin to your Pinterest board so you can come back when you need to whip up a DIY insecticidal spray again!
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