Whiteflies can seem to come out of nowhere all of a sudden! They are easy to identify. When you move or water your plants and you see what looks like an instant snowstorm with minute things flitting all over, you've got whiteflies! At the first sign of them you want to take action as they multiply like crazy.
Let's talk a bit about whiteflies and then we'll get to some controls. It always helps to understand the nature of the critter you are dealing with. Although all whiteflies tend to look alike, there are two major types, the greenhouse whitefly and the silverleaf whitefly. Whiteflies are not true flies as they are relatives of mealybugs, scales and aphids. The eggs are laid on the undersides of leaves. They are cone-shaped and range in color depending on species from from dark gray to burnt orange. The eggs are often laid in a circular or crescent pattern. If you see them, smash them. When the eggs hatch in 4-12 days what emerges is a white, flat, oval shaped nymph. They have no legs and can be mistaken for scale insects at times.It is the nymph and adult fly that cause physical damage to the host plants. They attack the leaves, buds and stems sucking the juice out of them. Without control infested plants will turn yellow, growth become stunted and ultimately die. Whiteflies produce honeydew (like aphids) that drips onto the plant encouraging the growth of sooty mold and they can spread plant viruses. Now we understand a little more about whiteflies and it’s time to get to the controls. These techniques may be used inside or out as you see fit.
Adult greenhouse whiteflies are slightly less than 1/8 inch long. They have a white, waxy coating and hold their wings parallel to the leaf surface.
Adult silverleaf whiteflies are a bit smaller than the greenhouse whitefly and they have a yellowish hue to them. They hold their slim wings at a 45-degree angle to the leaf surface. In more northern climates silverleaf whiteflies that have plagued us outside will die after a hard freeze. In the south the silverleaf whiteflies overwinter in the milder areas and come forth in spring when temperatures are consistently 65 F and above. We often bring home plants from greenhouses and nurseries, which have the greenhouse whiteflies.