Insecticides

Insecticidal Soap

The commercial insecticidal soap sells for $7.98 per quart. The homemade versions cost just pennies and do the same thing. I presented two different versions on KOTA Television.

Version # 1:

Mix two tablespoons of Ivory Soap Flakes powder with one quart of water. It will look a little milky. Put this in a quart spray bottle and use when you notice an infestation of white flies mites aphids thrips etc. Be sure to spray underneath the leaves too ... most of these critters like to hide!

Great-grandma used to pour her dishwater over plants that looked "sickly." She was using homemade insecticidal soap.

Version # 2.

Mix two tablespoons of Dawn Dishwashing Liquid with one quart of water and put in a spray bottle. Use for the same insects as the version # soap mixture.

When I spoke with my County Extension Agent he told me to warn folks that these are CONTACT sprays -- you have to squirt them directly on the insects.

He also cautioned against using these sprays OR the commercial version on a hot day as they can damage (burn) the foliage of the plants if you get too much on the leaves.

My own personal preference is the Ivory Soap spray because most dishwashing liquids are detergents and I do not know what they do to the environment.

Q. I have a lot of aphids on one of my roses. I need a homemade insecticide recipe. Years ago I had one that called for Listerine and soap. Do you have it? If not do you have a good recipe.

A. This is what one poster at Global Garden wrote:

"By the time I have gone out to buy liquid Ivory soap and Listerine I have spent a whole lot more than going down to my local garden/greenhouse supply and bought a bottle of insecticidal soap. I have had really good luck with these commercial products and have never lost a plant. I have used both the 'Safer' brand and several brands that employ pyrethrums (a natural insecticide derived from chrysanthemums). Each one contains ingredients that at one time or another has gotten rid of aphids white flies and spider mites on my plants. Check the labels to see what the product is effective against."

To make your roses unpalatable to aphids and other pests spray them with 1/2 cup Listerine and 1/2 cup water mixed with four drops of Ivory Liquid Soap [which makes the solution adhere to the plants]. Repeat spraying weekly for at least four weeks and reapply if there is rain in between since it will wash off.

But do not forget about ladybugs. They are a wonderfully beneficial insect for your garden and aphids are one of their favorite meals.

Q. Looking at a rose spray for insects and the active ingredient at 1% is Canola oil with the all famous inactive ingredient being just other (water?) On the net at they talk about using Canola oil as an insecticide. Any thoughts for this product for use as an insecticide? Can Canola cooking oil be used or is there a difference?

A. Thank you very much. Oils are used as a sticking agent. It makes the harsh killing chemicals adhere to the plants and insects thus increasing the ability to kill and thus protect the plants. Here is what the article above states in part:

"Scientists believe that canola oil repels insects by altering the outer layer of the leaf surface or by acting as an insect irritant."

That seems harmless enough for human beings and pets.

"Whether or not a substance poses a risk to humans or other organisms depends on two factors: how toxic the substance is and how much of it an organism is exposed to. Therefore the EPA considers both toxicity and exposure data in determining whether to approve a pesticide for use."

Here is where I would express reservations. I would like to see further research reports before using myself.

I would be careful about using your canola cooking oil as a spray. Remember you quoted 1%. I would wonder if that low percentage mixed with water would have any beneficial effect. I recommend other organic nontoxic solutions. You can view some reports at my GardeningWithGary website here.

Q. What is this oil that you spray on plants to kill insects? I am curious if it is not harmful to animals.

A. Dormant oil is a nontoxic spray to control insects before they can do anydamage since you spray the plants early before the insects have become adults. Use on fruit trees shrubs and evergreens in early spring while they are still dormant before buds develop. You can buy the spray from most garden centers or make your own using the following recipe from Garden Guides:

1 gallon mineral oil
1 pound soap (use fish oil soap if you can find it)
1/2 gallon water

Combine all ingredients boil and mix very well. Dilute 1:20 with water and use immediately because the ingredients separate quickly. Mix up only what you can use that morning.

Spray on a day when the temperature is above 40F and no freeze is forecast for at least 24 hours. Drench the branches of the shrubs and trees thoroughly.

For citrus trees buy a special dormant oil from your garden supply store because their leaves can be damaged by the film which remains on the leaves.

Q. I found a recipe in your question and answer section where Alice asked about the insecticide recipe including Listerine and soap. I would like to know if this also good for killing mosquitoes in the lawn and what would be the ratio for an average size lawn located in a subdivision. I am extremely allergic to mosquitoes and unfortunately my lawn saturates very easily and stays wet for long periods of time. I need to find something that will help me keep the mosquito population down and had heard that a recipe including Listerine soap and another ingredient worked very well when used regularly.

A. Try this formula:
Mix 1 cup each of Listerine? liquid dish soap and water. Add 2 cups lemon
juice [i.e. bottled from concentrate]. Spray on lawn and around plants. Apply in the morning and if it rains reapply. Otherwise treat lawn once every two weeks. Avoid wearing any strong perfume deodorant cologne or suntan lotion. Burn citronella candles around badly infested areas and patios where you sit. Remove any items with standing water. A bird bath must be emptied and cleaned at least twice a week. Kill mosquito larvae in ponds and puddles by sprinkling in plain powdered coffee or tea just enough to change the color of the water. Caffeine makes mosquito larvae uncoordinated.