Jimster & I were discussing this some time ago. Several recipes were given, including one from the USDA... but the thread seems to have dropped off the active list. Fortunately, I saved Jimster's post in my clippings:

posted by: jimster on 10.18.2006 at 08:26 pm in Vegetable Gardening Forum

"It was only after reading this thread that I remembered saving a couple of recipes last year -- recipes which would have been useful this year if I had remembered sooner.

INSECTICIDE: A U.S.D.A. formula combining oil and soap is effective in killing soft-bodied insects. Mix 1 cup peanut, safflower, corn, soybean, or sunflower oil with 1 tablespoon liquid dishwashing detergent. To make the spray, use 11/2 teaspoons of the oil-detergent mixture for each cup of water...."

This question comes up fairly frequently, so I'll try to keep this formula posted, in the event that it disappears from my clippings (as some posts already have).

I've had good luck adding 1 tsp. of sugar to the soap spray; it will kill even cucumber beetles, if they are completely saturated. It is also highly effective against squash bugs, both adults & nymphs. Soap sprays in general tend to burn foliage, so they should be targeted on the insect pests directly, not sprayed over a wide area. If large leaf surfaces are sprayed, they should be rinsed as soon as the insects have died, about 1 hour after application.

For wider infestations, it might be better to use an insecticidal soap such as Safers, which is less likely to cause severe leaf burn. Safers also qualifies as organic... dish soap, while non-toxic, may not meet that qualification.

A mixture of soapy water & rubbing alcohol in a spray bottle will kill wasps... it literally knocks them out of the air. The bottle should have a strong spray, such as the horse spray bottles sold in Farm & Fleet stores.

Hi zeedman,
Some insects are eating leaves of my eggplants leaving tiney holes on them.Please let me know if you any recipe for this.

Chamen, it sounds like flee beetles. They were a real pest for me when I lived in California. I still see them in my garden here, but they don't do much damage... something appears to be controlling their population naturally.

Flee beetles are a little tough to kill, and since they are spread out over a large area (as opposed to grouped together), they need a spray that is broad-coverage. That rules out dish soap. Insecticidal soap alone won't kill them, but mixed with rotenone, it might kill enough to prevent severe damage.

Personally, I don't like broad-coverage sprays of any type, and seldom use them. They kill not only the pest targeted, but any natural insect predators that might be present. The predator population is usually slower to recover, while the pest multiplies quickly - so over time, such spraying can actually make the problem worse. I usually just tolerate insect damage, unless it becomes severe.

Say, will that recipe kill Tomato horn worms? I dont seem to have any of the wasps that usually infect the worms. I have been picking them off the plants but there is always one more the next day.

Our family has used the beer trick for Tomato horn worms for generations. Place a small cup (like a cut-in-half red solo cup) filled with beer near the plants. Use several for a good size garden. I use one between every two plants. This works pretty well for me. Good luck with it!