Whiteflies only measure approximately 1/10 to 1/16 of an inch in size, but they can create big problems for your garden when they feed on your plants. In fact, whiteflies are one of the most common pests you'll notice in your backyard. While you have several options for controlling and eradicating whiteflies, you first need to identify this pest and learn to read the signs to accurately determine that it's the source of your plant problems.
Plant Foliage Signs
Whiteflies leave some telltale signs on plant foliage during and after an infestation. Because whiteflies bite into a plant's leaves and suck out its sap, leaves often turn yellow or appear to become dead and dry. In more severe cases of whitefly infestations, complete leaf drop may occur, leaving behind bare stems and twigs. Additionally, some types of whiteflies cause distortion of the plant foliage, such as curling or patchy discoloration.
The physical presence of whiteflies are a dead giveaway that you have an infestation problem. Because they multiply so quickly -- a single adult will lay up to 400 eggs -- it's important to inspect plants constantly. Check the undersides of your plant's leaves, which is where whiteflies congregate. They appear as small, white-dusted flies or moths that quickly erupt into a white cloud when disturbed. Eggs appear as tiny, waxy white dots on the underside of the leaf, often arranged in a circular pattern.
Honeydew, Ants and Mold
As the adult whiteflies feed on your plant's sap, they produce a sticky, sweet substance known as honeydew. This is much like what happens when aphids and other sap-sucking insects feed on your plants. And just as with aphids, the presence of whiteflies and their honeydew is also often linked to the appearance of ants, which are attracted to the honeydew. Additionally, the honeydew from whiteflies sometimes produces a secondary problem: black mold that grows on the honeydew.
Whitefly Control and Eradication
After identifying the signs that whiteflies have attacked your plants, take control of the situation and eradicate this pest before it causes leaf drop and plant death. Inspect your plants regularly. Remove any foliage that show signs of whitefly activity by cutting the leaves off with clean shears and discarding the leaves immediately. This often helps keep the pest population at levels that are low enough for general plant health. Alternatively, try trapping the whiteflies. Use cardboard or paper that's bright yellow -- the yellow color attracts this insect -- and coat it with a mixture that's 1 part soap detergent and 1 part petroleum jelly. Hang the trap on or near your affected plants. The whiteflies will land on the yellow surface and get stuck and die.