If we were making a list of the most frustrating struggles that every single gardener and farmer knows all-too-well, the number one spot would have to go to pest control. The hours of labor and love you have invested can feel like it has all been for nothing when you see your precious plants become home to detrimental insect invaders or invasive fungi spores like powdery mildew. But thankfully, one of the best tools for fighting all of these pests can be found right under your cabinet: Soap!
Whether you’re dealing with aphids, whiteflies, mites, or beetles, homemade soap spray is a tried and true method for eliminating insects.
Unfortunately, however, most products that are sold commercially as “soaps” are actually detergents that are full of harsh chemicals, including degreasing agents which are much too strong to be used on delicate plant tissues. Many of these products also contain antibacterial ingredients that will destroy beneficial microorganisms and disrupt the plant’s delicate ecosystem.
Over the years, many frustrated plant growers have tried making homemade soap spray out of almost every type of soap, from dish soap to body soap, and from soaps with all-natural ingredients to commercial “soaps” made with synthetic cleansers.
It may come as a surprise that the liquid castile soap is best known for gently cleansing your skin is the same soap that is best at eliminating and preventing pests. But those who have come to be more familiar with the many wonders of castile soap probably aren’t too surprised. Castile soap is made from all-natural oils, which makes it a much gentler and safer option than synthetic detergents, allowing you to control garden pests while ensuring as little risk as possible to your plants.
It should be noted that many soaps, including castile soaps, include fragrance oils that may be harmful to plants. When choosing which soap to use for your DIY liquid-castile-based soap spray, we highly recommend sticking to unscented liquid castile soap.
As we mention below, in some cases it may be beneficial to use peppermint and/or eucalyptus oils for their additional insect-repellent properties, in which case our Peppermint & Eucalyptus liquid castile soap is another excellent choice for these applications.
How To Make Liquid Castile Soap Spray for Pest Control
Preparation: Gather Your Materials
- Unscented Liquid Castile soap, or Peppermint & Eucalyptus for an added punch
- One tablespoon for a quart-sized batch
- Five tablespoons for a gallon-sized batch
Note: In cases of light infestation or fragile plants, we recommend using half of the suggested amounts of liquid castile soap.
- Fresh filtered or distilled water
- Smaller batch: One quart
- Larger batch: One gallon
Note: If necessary, you may use tap water instead of distilled or filtered water, but the effectiveness of the soap spray will be decreased if using hard water. Also, remember that solutions made with unfiltered tap water should not be kept for more than a few days due to the potential for bacterial growth.
- Large, empty, clean bucket or another container for mixing.
Note: Make sure this container is large enough to hold the amount of liquid you are using, either 32.5 ounces for a smaller batch or 130.5 ounces for a larger batch (plus any added essential oils).
- Spray bottle
Note: This is a good opportunity to repurpose any old plastic spray bottles from commercial cleaners. Just make sure to thoroughly rinse with warm soapy water first to remove any leftover chemical residue.
Optional Materials:
- Masking tape and marker for label
- 1 tbsp of neem oil
- A few drops of peppermint oil, if using Unscented.
Optional Preparatory Step:
We highly recommend labeling your bottle first, while it is still empty and dry. Especially when storing your pest-control spray along with other similar-but-different types of DIY Castile-based spray solutions – such as Castile-based All-Purpose Cleaner or Castile-based Produce Wash – we find it to be very helpful to keep all of our bottles labelled. Of course, this can be done any time in any way you choose, but we find it easiest to do this step first.
Step 1:
Fill your larger container with your chosen amount of distilled or filtered water.
- One quart for small batch
- One gallon for larger batch
Step 2:
Add liquid castile soap to water.
- 1/2 to 3/4 tablespoon (0.25-0.37oz) for small batch
- Two to three tablespoons (1-1.5oz) for large batch
Step 3:
Stir gently to combine. Try not to create too many suds.
Step 4:
Pour the solution into a spray bottle. If made with filtered or distilled water, the excess solution can be stored indefinitely.
Step 5:
Spray the soap spray on and around your plants, making sure to thoroughly saturate any areas where the insects are seen.
Optional Additions for Extra Effectiveness:
In cases where the soap spray alone has been less effective than desired, you can boost its strength by adding neem oil and/or a small amount of peppermint oil if you used unscented Castile the first time around.
- 1/4 tablespoon of neem oil for a small batch.
- One tablespoon of neem oil for a larger batch.
If adding neem, it’s important to properly emulsify first.
Step 1
Add all neem oil and castile soap to a shaker bottle or blender.
Step 2
Add a few cups of warm water and blend or shake until the solution is an even white color.
Step 3
Add solution to the sprayer with the rest of the water needed. Mix well and apply.
- If desired, you can also add 5-10 drops of peppermint oil.
How To Make Liquid Castile Soap Spray for Ant Deterrent
Preparation: Gather Your Materials
- Gather all materials listed above for pest control soap spray.
- Essential oils for ant repellent:
- Tea Tree Oil
- Peppermint Oil
- Eucalyptus Oil
Step 1:
Prepare pest-control soap spray as described above, except quadruple the amount of liquid castile soap used.
- For a smaller batch, add ¼ cup (four tablespoons) of liquid castile soap to one quart of water.
- For a larger batch, add one cup of liquid castile soap to one gallon of water.
Step 2:
Add 5-10 drops of each essential oil (tea tree, peppermint, and eucalyptus).
Step 3:
Mix solution gently but thoroughly. Avoid creating suds.
Step 4:
Pour the solution into a spray bottle. If made with filtered or distilled water, the excess solution can be stored indefinitely.
Step 5:
Spray the soap spray on and around anywhere you see ants, including door and window frames and baseboards. Spray should be used both indoors and outdoors.
Note: Wet weather tends to encourage insects to move indoors. To help increase your repellent’s effectiveness during these times, apply an extra layer of spray as a preventative measure when expecting rain.
IMPORTANT NOTE: Do not apply this concentration of soap spray directly to plant foliage or soil, as it will burn the plants’ tissues.
We believe that our liquid castile soap is the best type of soap to use for killing and repelling invasive insects while protecting the health of your plants. It is able to destroy soft-bodied insects and harmful bacterias while remaining gentle enough to avoid harming your plants’ delicate tissues or disrupting beneficial microorganic life. However, there are some exceptions when using any soap spray, including full-strength Castile-based soap spray, would not be advised.
Even gentle castile soap can be too strong for young or newly transplanted plants and can be especially harmful to soft-bodied larvae of beneficial species such as ladybugs, as well. If you decide to use a soap spray on or around more fragile plants or vulnerable beneficial species of insect, we recommend making your soap spray half as concentrated as our recipe instructs. This will allow you to get the most bug-killing benefits with the least risk to vulnerable plant tissues. Additionally, neem oil should not be used on recent transplants or otherwise-stressed plants, as it can burn their foliage even in lower concentrations.
Check out our brand new Liquid Castile Soap in the “Soap + Shampoo Bars” section of our Growing Organic Shop. This is the latest addition to our Lactosoapcillus line of all-natural probiotic and vegan soaps, and you can count on it to deliver all of the same skin-loving probiotic benefits that you have come to love. We are happy to offer four customer-favorite, all-natural scents of liquid castile soap, including “Frankincense, Tea Tree & Lavender” “Lavender”, “Patchouli”, and “Peppermint and Eucalyptus”, as well as an “Unscented” option.
If you have any questions, suggestions, or feedback, as always please don’t hesitate to reach out to us.
Happy Pest-free Growing!
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