How to Make Your Own All-Natural Pesticide: Mix 1 gallon of water with 2 tablespoons of neem, and ½ teaspoon each rosemary and lavender essential oils. You can also add a couple of tablespoons of phosphate-free liquid dishwashing soap. Mix thoroughly and pour into a spray bottle. Spray over every part of your plants, mixing frequently to keep the oils and water from separating.