Mixing soap that has no synthetic chemicals, degreasers or skin moisturizers with pure water produces insecticidal soap suitable for use on gardens and houseplants. The fatty acids of the soap dissolve the exoskeletons of many insects including mites, thrips, aphids, white flies and immature leafhoppers. This soap is typically poured into a spray bottle for convenient application.
Making insecticidal soap requires only soap and water. First clean the spray bottle to remove any residue that might harm plants. Mix the soap and water solution using one tablespoon of soap per quart of water. Spray plants immediately from top to bottom, ensuring an even coating. Not every plant is able to tolerate insecticidal soap, and some may show signs of browning, spotting or wilting. Test the soap on a few isolated leaves before coating the rest of the plant.
Hard water may affect the quality and effectiveness of insecticidal soap. Bottled water may be a more ideal choice in homes where water supplies contain high quantities of sediment. Detergents, dish soaps and products that contain synthetic chemicals are not suitable for creating insecticidal soap as they lack the animal and vegetable fats needed to exterminate insects. Some recipes call for additional ingredients such as cayenne or red pepper, garlic, powerful herbs and extracts or vinegar, which may increase their effectiveness against certain types of pests.