Here is a homemade insecticide that is easy to manufacture and relatively efficient.
Add a clove of garlic and two cups of water to a blender and run at high speed until the garlic is reduced into a purée. Pour the resulting mash into a container, cover and let it sit for a day. Next pass it through cheesecloth or a sieve to remove the pulp. Mix the resulting solution into 1 gallon (4 liters) of water, adding a spoonful of insecticidal soap to improve its adhesion. Now spray on plants infested with aphids, whiteflies and other insects. This insecticide has no residual or preventative effect: it must touch the insect to be effective.
And apparently it is also effective against vampires!