Herbal insecticide

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From Mother Earth News, Jul 1995

Allegedly good for deterring aphids and Japanese beetles, not so hot on cabbage moths and worms. Spray every morning for a week or two until you start to see results, then once a week to keep the bugs away.

Wanda's bug spray

1 quart cool tap water

4 green stalks and bulbs of winter onions

4 cloves garlic

2 tbs red pepper flakes

6 tbs dishwashing liquid

2 x 1 quart canning jars with screw-on lids

1 cup strainer (with a screen sieve)

1 plastic water mister

Place peeled and chopped onion and garlic in a quart jar. Add red pepper and dishwashing liquid, and fill to the rim with water. Tighten the lid and shake vigorously. Place your concoction in the sun to brew for a few days. Store in the shade. When you need it, strain the liquid into your second jar or your mister. Add water to your old batch to replenish what you've taken. Eventually, compost what remains and start fresh.

-- Old Git (anon@spamproblems.com), April 25, 1999


I'd heard that the novel ideas of using dishwasher liquid for these kinds of sprays had been found to have harmful effects on the plants, but I can't remember the details. You might want to look into this Old Git since you're doing such awesome research and sharing for us here!

PJ in TX

-- PJ Gaenir (fire@firedocs.com), April 26, 1999.

Hadn't heard that, PJ, thanks for bringing it up. It was definitely worth a quick surf and the result follows from Washington SU. Thanks to your suggestion I also found a super site with lots of recipes for home-made stuff--I'll clean it up and post it later.


Guidelines for Insecticidal Soap

All soaps are long chain fatty acids, but not all soaps have inseciticidal properties. Insecticidal soaps are specifically formulated to have high insect-killing properties, while being safe for most plant species.

Insecticidal Soap is a Contact Material

Insecticidal soaps kill susceptible insects by washing away the protective coating on the surface of the insect and by disrupting normal membrane functions inside the insect. The insects must come into direct contact with the spray droplets for the material to be effective. Good coverage is essential. The soaps have no residual activity toward insects, but repeated applications may have damaging effects on some types of plants.

Water Quality and Insecticidal Soap Effectiveness

Water hardness reduces the effectiveness of insecticidal soaps. Calcium, magnesium and iron precipitate the fatty acids and render them useless against the insects. It is important to use the purest water possible. Conduct a "jar test" to determine if your water is compatible with the soap. Mix the concentration of soap that you intend to use with water in a glass jar. Mix and allow to stand 15 minutes. If the mix remains uniform and milky, then your water quality is adequate. If a scum develops on the surface of the water, then conditioning of the water will be necessary. The water can be conditioned using a commercially available anionic buffering and conditioning agent. Some readily available products such as "Calgon" may be used. Insecticidal soaps may foam; if your sprayer has an agitator, a defoaming agent may also be added.

Spray Coverage

Good spray coverage is essential for adequate results. Spray equipment must be clean and operating at peak efficiency. The proper configuration of nozzles for good coverage must by utilized in order to wet both sides of the leaves and growing points of the plants. Some of the new spray technologies that create a "fog-like" spray may also improve coverage. Spraying in the evening or early morning hours so that the spray droplets do not dry out quickly may also improve the effectiveness application.


Insecticidal soaps may cause a burn on the foliage of sensitive plants. In general, some cole crops and certain ornamentals are sensitive to burn caused by soaps. Multiple applications in a short time interval can aggravate phytotoxicity. In addition, water conditioning agents can increase phytotoxicity. A small spray strip should be applied and observed before a full-scale application is made if there is a question concerning sensitivity.


The concentration of the spray is more important than the amount of soap applied. Usually insecticidal soaps are used as a 2% solution. If water is increased or decreased, then the amount of soap must be increased or decreased accordingly.

Pests Controlled

Insecticidal soaps are used against soft bodied insects and mites such as aphids, thrips, white flies, spider mites and immature leafhoppers. Insecticidal soaps have been about 40-50% effective against these pests. Repeated applications may be necessary to adequately control high populations of pests, and close attention should be paid to all details outlined above to achieve maximum control.

Application Safety

Even though soaps have low toxicity to humans, they should always be used with caution. Read and follow all label directions.

Trade names are not intended as an endorsement.

-- Old Git (anon@spamproblems.com), April 26, 1999.

However, the soap in the recipe has NOTHING to do with the insect repellent features of the "tea". The soap is used as a surfactant, or "sticker" in the gardening/lawn maintenance vernacular. It keeps the "tea" on the leaves and other surfaces. It also spreads the tea out.

Chuck, who used to use the ubiquitous AMWAY LOC for this purpose.

-- chuck, a Night Driver (rienzoo@en.com), April 26, 1999.

My folks were totally against commercial insecticide in the garden, so mother used lye soap water to keep down the pests. Long after she quit using lye soap for laundry, she still made it for the garden. And long after she had running water, and several outside faucets, she still saved her wash water to water her plants.

Thanks for posting all the garden stuff Old Git. I used to start sweet potatoes for plants, when I was a kid, in a jar of water with toothpicks to hold it up. Once mother put one in the garden and we had lots of sweet potatoes. Now I don't even remember how I did it, or which end goes in the water. Does someone remember? I love sweet potatoes and would like to plant some.

-- gilda (jess@listbot.com), April 26, 1999.

PJ - There is a major difference in toxicity in what you referred to as "dishwashER" liquid, and a mild "dishwashING" liquid like ivory snow. Use the mildest hand washing liquid available.

-- Brooks (brooksbie@hotmail.com), April 26, 1999.

Gilda -- (sweet potato question): "which end goes in the water"?

I dunno. Take 2 jars. Put one sweet potato in up and the other in down. Observe. A few days should do it.... [:=}

-- Tom Carey (tomcarey@mindspring.com), April 27, 1999.

Old, PJ -

From dust memory stacks, topic: dish soaps (Joy, Dove, Dawn, etc)as surfactants (sp?)and insecticides in homemade plant remedies. Well, the pages are dusty and faded (but an older copy of OG will probably confirm) the problem is soap formulations. As I recall, went something like this: you brew your remedy using soap x and test it. Works fine, no burning. So you mix big batches and use without incident. You get a new bottle of soap, mix it up and this time wipe out your garden. The claim is that the time you brewed up the next batch, the maker of soap x has changed the formulation based on cost of materials, grease cutting power, or whatever.

In anyevent the upside of dish soap is it is cheap, the downside of dish soap is you really need to test each bottle's effect on you plants. Insecticidal soaps are more expensive than dishsoaps, but the the formulations are constant and/or pretested for toxicity to your plants.


The Amway LOC idea is interesting. (Truth in advertising disclaimer - I am an inactive Amway distributor) As I recall - LOC is very concentrated, gentle, and biodegradable - however I have never used it in mixing up plant treatments. A little would go a long way. If you've used it, I'd appreciate mixing proportions that have worked for you. Thanks


-- john hebert (jt_hebert@hotmail.com), April 27, 1999.

To the top for newbies and others who're interested.

-- Old Git (anon@spamproblems.com), June 26, 1999.

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