White flies are attracted to the color yellow. There are products out there that are white fly sticky traps. Follow the directions on the box the traps come in. The adults fly over and get stuck. Note the recommendations regarding the placement of the traps relative to the infested plants. The traps help knock the adult population down and then wash down the plants with a jet of water and once that dries, spray with insecticidal soap....read the directions on that too, especially the details regarding coverage and timing of applications (timing regarding outside temperatures AND frequency of applications due to the life cycle of the pest).
Netting would only help if you were sure there weren't already any whiteflies already on the plants, the net would just protect them inside the net!
