Whiteflies have piercing-sucking mouthparts with which they use to pierce a plant and extract the juices. The whitefly sucks more plant juice than they can digest and as a result excrete large amounts of honeydew beneath the leaf. This honeydew causes mold to form which kills the plants.
Though whiteflies are extremely deleterious to plants, their bite is not considered a threat to humans. Their close cousin the thrip, on the other hand, does use its piercing-sucking mouthpart to bite humans. [Potter, ipm.ifas.ufl.edu]
The whitefly is part of the order Homoptera. This means literally “same wing.” It refers to the fact that the wings seem to attach seamlessly to the body due to a membrane. Grasshoppers and aphids are also part of this order. The whitefly can be identified by its white powdery coloration and its small moth-like wings. Its head includes antennae and the mouth is shaped like a beak. This makes it ideal for sucking. The head is a slightly yellowish color in comparison to the white wings but unless looking very closely, the whitefly appears to be completely white.
Whiteflies have the ability to become resistant to pesticides very quickly. Because of this, it is generally best to use a biological means to treat a whitefly infestation. Predator insects such as ladybugs and green lacewings can be used to eat the whitefly larvae and eggs. Cleaning the plant leaves frequently to remove the eggs and honeydew residue can help as well. You may wish to try sticky paper to catch the adult whiteflies. It is best to use a brightly colored paper such as yellow to attract the whiteflies.