My compost makes whiteflies. I kind of like them, they look like little spirits floating around. Apparently, many people view them as pests, as they can breed very quickly and feed on your plants, so I looked into ways to control the population and the short answer was hummingbirds and ladybugs. I do have a couple resident hummers in the garden, so perhaps that's why I don't have an infestation of them, there's just always a dozen or so floating around. If you are lucky enough to have beetles and dragonflies, they also help.