Here are two organic recipes for killing soft body insects in your garden.
1. Mix one cup of canola oil into a gallon of water. Spray the mix on the plants and it will suffocate the insects. Don’t use more oil as it could harm your plants.
2. Take one garlic bulb, mix it with two cups of water and let it stand overnight. The following day, strain it and mix one gallon of water and spray it on your plants.
Cranberry Compost & Gardening Blog 
May 29, 2011 @ 14:33:23
To make the garlic spray do you chop up the garlic and soak it in the water? It doesn’t say how to handle the garlic and it seems strange to just throw in a whole unpeeled bulb of garlic. And, how long does it last when sprayed onto your veggies? Thanks.
May 29, 2011 @ 21:14:29
You don’t have to chop up the garlic. However… I would definitely peel it first. But I think that chopping it up a little or smashing it some would probably help!
To be honest… I don’t know how long this will last when sprayed on your plants. I have been very lucky and haven’t had a lot of bug problems here, so haven’t had to use this type of thing very often. But if you try it, please come back and let us know!
Jun 04, 2011 @ 09:23:20
Here is another recipe I found that is similar and also has more detail on how long it lasts.
Onion and Garlic Spray
Mince one organic clove of garlic and one medium sized organic onion. Add to a quart of water. Wait one hour and then add one teaspoon of cayenne pepper and one tablespoon of liquid soap to the mix. This organic spray will hold its potency for one week if stored in the refrigerator.
I found this recipe here: http://www.globalhealingcenter.com/natural-health/organic-pesticides/