Gardeners have been using herbal insecticides as a safe alternative to chemical based insecticides for thousands of years. Though many herbs, including rosemary, ginger and bay leaf, can kill and deter insects in your garden, they are generally safer for small children and pets than commercial, chemical-based insecticides. Preserving the herb in a plant-based oil both maintains the beneficial properties of the herb and creates a compound that can be sprayed, spread or mixed easily.
Place 4 ounces of fresh rosemary at the bottom of the clear glass jar. Pour in enough safflower oil to cover the herbs. Close the jar with the cover and place in a warm, sunny spot for at least two days.
Open the jar and pour oil through the strainer into the measuring cup. Discard the remaining herbs.
Pour 2 ounces of the strained oil into the spray bottle. Add 2 ounces of liquid soap and 8 ounces of water.
Shake bottle until mixture is blended. Shake the bottle before every use, because the components will separate.
Spray evenly over the plants to be treated. Hold the bottle at least 12 inches away from the plants when you spray.