HOW TO PREVENT WHITEFLIES
Keeping natural predators around will prevent whiteflies from ever exploding in population. Ladybugs, spiders, lacewing larvae, and dragonflies are a few of many beneficial insects that can control a whitefly population. Hummingbirds are another natural predator. Try creating a habitat that will attract dragonflies and damselflies (which also helpfully eat mosquitoes) or beautiful hummingbirds.
When it comes to whiteflies, avoid chemical insecticides; they’re usually resistant and all you end up doing is killing the beneficial insects—their natural predators—and the insects which pollinate the garden for a better harvest!
Mulch early in the season with aluminum reflective mulch, especially when it comes to tomatoes and peppers. The reflective mulch makes it challenging for whiteflies to find their host plants.
Set out yellow index cards coated with petroleum jelly to monitor whiteflies, especially when it comes to tomatoes, peppers, sweet potatoes, or cabbage crops. A half-and-half mixture of petroleum jelly and dishwashing detergent, spread over small boards painted bright yellow, is sticky enough to catch little whiteflies, too. To whiteflies, the color yellow looks like a mass of new foliage. The bugs are attracted to the cards, get stuck in the jelly, and die.