The Signs of Whitefly

Ants on or near the plants could indicate whitefly activity.

Ants on or near the plants could indicate whitefly activity.

Whiteflies are sucking insects that feed on the sap of a broad range of plants. Promptly recognizing the insect pests attacking your prized plants as whiteflies will guide your treatment decisions and help to minimize further damage. In some situations, whitefly adults or nymphs may be visible on plants. Otherwise, you will have to recognize other indications of whitefly activity.

Recognizing Whiteflies

Whitefly adults measure about 1/16 inch long and resemble tiny moths, with delicate wings that are covered with a powdery white wax. Whitefly numbers increase rapidly when weather is warm and natural enemies are lacking. If you disturb a plant that is heavily infested with whiteflies, a cloud of the insects will fly up off of the plant. Adult females lay eggs on leaf undersides. Nymphs are mostly immobile, appearing as bumps on leaf undersides. Whitefly adults or older nymphs often have distinctive markings you can use to identify the species. For example, the nymphs of the wooly whitefly (Aleurothrixus floccosus) are covered with fluffy, waxy filaments while iris whitefly (Aleyrodes spiraeoides) adults have a dot on each wing.

Damage to Plants

Whitefly adults and developing nymphs feed on fluids sucked out of plant tissue. They almost exclusively feed on leaves and, more specifically, leaf undersides. This feeding weakens plants, causing leaves to turn yellow, look dry or fall off plants early. A severe infestation can cause a loss of vigor, stunt plant growth or cause wilting.


Whiteflies are unable to completely digest all of the sap they suck out of plants and excrete, as a byproduct of feeding, a sugary substance known as honeydew. This sweet material looks shiny or sticky where it drips down onto the ground, other plant parts and any other objects under where the whiteflies are feeding. Sugary honeydew attracts ants, which in turn protect whiteflies from their natural predators. Honeydew also hosts the growth of an unsightly fungus, sooty mold.

Similar Symptoms

A handful of other pests can cause damage potentially mistaken for whitefly activity. Aphids are soft-bodied, winged insects whose feeding can cause leaf yellowing, leaf drop and stunted or distorted growth. Aphids also secrete honeydew and are different than other insect pests because they have a pair of tubelike structures projecting out of their rear. Scale insects appear as immobile bumps where they feed. Some scale relatives, mealybugs, are slow-moving and covered with a waxy white material but lack wings. Mealybugs and some species of scale produce honeydew.

About the Author


Photo Credits

  • Jupiterimages/ Images
Suggest a Correction