When used incorrectly, pesticides can pollute water. They also kill beneficial as well as harmful insects. Natural alternatives prevent both of these events from occurring and save you money. Consider using natural alternatives for chemical pesticides: Non-detergent insecticidal soaps, garlic, hot pepper sprays, 1 teaspoon of liquid soap in a gallon of water, used dishwater, or forceful stream of water to dislodge insects.