To make an insecticide for whiteflies at home, pour 1 cup of vegetable oil into a sealable bottle, add 1 tablespoon of regular dish soap, and shake the bottle until the liquids mix together. Before using the insecticide, pour 1 cup of water into a spray bottle, add 1 1/2 teaspoons of the insecticide to the water, and shake the bottle frequently while applying the mixture, as oil and water don't mix permanently.
Alternatively, pour five parts water, two parts rubbing alcohol and 1 tablespoon of dish soap into a spray bottle, and shake the bottle well to mix the liquids. Users need to test this insecticide on one leaf of the plant, as rubbing alcohol might affect some plants badly.
When using an insecticide in a form of a spray, make sure to apply the spray to both top and underside of the leaves, as whiteflies often stay on the underside. It is important to apply the insecticide generously, as small larvae and eggs need to be covered in spray to get killed. If the spray gets washed off by rain or during watering, repeat the application process again. It is better to apply the insecticide early in the morning or late in the day because the weather is colder during those parts of the day. Warm weather can cause an adverse reaction on the leaves.