To use garlic as an insecticide, blend fresh bulbs with hot peppers and water, strain, dilute, and add to a spray bottle with vegetable oil. Apply to plants on mild days, once a week, to deter insects such as aphids, loopers, whiteflies and leafminers. Alternatively, use a mix of garlic, mineral oil, fish emulsion and castile soap to make an insecticide solution that also helps repel rabbits from gardens.
To make a simple garlic and pepper insecticide spray, combine 2 bulbs of garlic with 2 hot peppers in a blender. Add 1/2 cup of water, and blend for several minutes. Strain over cheesecloth into a glass jar, and dilute at a ratio of 1/4 mixture for every 1 gallon of water used. Add 2 tablespoons of vegetable oil for a more potent mixture.
Another option is to make a garlic and fish emulsion spray, effective for repelling insects and rabbits. Combine 3 ounces of minced garlic with 1 ounce of mineral oil, soak for 24 hours, and then strain. Mix 1 teaspoon of fish emulsion, 16 ounces of water and 1 tablespoon of castile soap. Combine the fish emulsion water with the garlic oil in a sealed glass container. When ready to use, mix 2 tablespoons with 1 pint of water in a spray bottle.