Natural remedies that work just as well or better than insecticides include the following:
Safer-Soap (registered trademark) works well and helps to dislodge the whiteflies from the plant. Spray weekly and follow directions on the back of the bottle.
Home-made wash recipe: blend three large onions, one hot pepper pod or three tablespoons cayenne pepper, one teaspoon vegetable oil, and one garlic bulb. Cover mixture with a little bit of water and let stand overnight. Sieve and put into one-gallong jug and top it off with water. Spray weekly or more often for heavy infestations.
Home-made remedy: Remove leaves with egg patterns. (They'll be sucked dry
anyway.) Cut out a piece of yellow or orange cardboard and coat with petroleum
jelly or Vicks VapoRub. Stick the coated cardboard into the soil next to the
plant. Shake the plant and the flying insects, attracted to the yellow color,
will unwittingly "stick" themselves to the cardboard. do this everyday until you
no longer see the tiny white fliers flitting around anymore.
Whiteflies are known to be attracted to the color yellow. If you take some yellow strips of paper and apply an adhesive to it, you can position these around your garden or on the tops of your plants containers as makeshift "whitefly traps". If these strips and just a few encarsia formosa are added at the beginning of your garden whitefly and a few other types of insercts will always be kept in constant check. Good luck with your whitefly problems and happy gardening!