There are multiple scenarios that can cause a whitefly infestation. One is the use of nitrogen-rich fertilizers. When plant tissues contain high nitrogen levels, whiteflies can flock to them. Another is during drought conditions, this is when these pests can flourish; they reproduce more quickly in hot weather—and dry conditions favor insects that, like the whitefly, have piercing mouthparts used to suck on plants. Plus, drought conditions can kill ladybugs, a natural predator of whiteflies. Finally, insecticides that kill off a wide swath of bugs can also eliminate the whitefly-eating ladybugs along with other predators of the pest (such as spiders and some wasps), which can allow whiteflies to thrive.