Oils as Insecticides

Oils as Insecticides

According to a recent Wall Street Journal report, entomologists at the USDA research lab in Phoenix, Arizona, were able to control garden pests with a cheap, nontoxic, homemade insecticide. The ingredients: dish detergent and oil!

Researchers found that a spray of soybean oil protected cotton from aphids and whiteflies, spider mites and beet army worms. It's also been used successfully on eggplants, carrots, lettuce, celery, watermelon, pepper and cucumbers. The mixture tends to burn the leaves of squash, cauliflower and red cabbage, though. Burning (phytotoxicity) might also occur with broccoli, collard, and squash; more research is needed.

How does it work? Mineral and plant oils are considered physical poisons that interfere with insect respiration. However, other modes of action may also occur. Soybean and cottonseed oil, among others, demonstrate repellant activity to several insect and mite species.

Here's the recipe:

Mix one tablespoon of dishwashing detergent with one cup of cooking oil (the detergent causes the oil to emulsify in the water). Mix one to two-and-a-half teaspoons of the mixture with each cup of water.

Spray on plants every 10 days with a pump sprayer. Morning and late-afternoon applications are better with regard to phytotoxicity.

According to the researchers, thirty cents worth of the homemade mix is as effective as a dollar's worth of store-bought insecticide. Not to mention safer!

References: Southwestern Entomologist, Sept. 1990.
Personal communication with USDA Research Lab staff,
Phoenix, Arizona, March 1991.
http://outreach.missouri.edu/hesnutrnews/fnr88-97/fnr91-3.htm

Darius, woulndt it be great if all the big producers/farmers started using this formula?
I'll try to pass the word alround here in this third world country.....

There has always been a problem in using oil as a spray additive and that is temperature. At 85 or so, foliage of many plants will burn. I currently use light sun oil, 3Tb to gal of water under 85 and 11/2 Tb over 85. A spurt of dish wash deterrengent helps spray to spread evenly.
My 2 cents.

Had a major whitefly problem with my Brugs in the basement I'm overwintering. Tried several things, finally used a oil mixture (cottonseed oil) and it got rid of them.

Paul

This wonderful mixture is much like what our grandparents applied when they threw out the dish, bath, and laundry waters in the gardens. And they had nice organic produce to feed their families. Nowadays we have dishwashers, automatic washing machines and the bath water goes down the drains thereby depriving us of these wonderful insectidal waters. I like to use hot pepper oil made with vegetable oil in the solutions I make. I also sometimes make solutions with datura and rhubarb leaves and spray the plants before the produce begins to form. I have to be careful not to get this or the hot pepper spray on the produce as it will last there for some time making it imparative that the produce be washed before eating it.

Wow. Does that bring back memories. When I was a kid we would visit my aunt's house in PA and she had a plastic bin in the sink while she washed dishes. When she was done she would open the door and dump that dishwater out on her rose bushes. She had the most stunning roses bushes I ever saw. I had forgotten all about that, but now that I think about it, the tiny bits of food would feed the plants as well as watering them and keeping the bugs off. Hmmmm....maybe instead of letting the dish water go down the drain I will get one of those plastic bins and take that dish water out the door and water the plants on my front porch!!

Leaflady - I could just hug you for bringing back that warm and fuzzy memory!

My family already laughs at me for all the things I throw in the garden. Now they'll have new fodder. Thanks for the great tip.

Welcome to DG, mickgene!

Thank you. Glad to be here. I've gotten a lot of good info during the last week that I've really gotten into the sight, but I'm afraid I may be spending waaay too much time here. (I started a journal yesterday....)