WHITEFLIES

INTRODUCTION:

Whiteflies are tiny insects that attack hundreds of different types of plants from tomatoes to gardenias to beans to greenhouse plants. They feed on the sap of the leaf and produce honeydew on the leaf, which supports the formation of molds. The plants undergo stress from loss of sap and attack by fungus. Frequently the first time you notice a whitefly problem is when a cloud of small white flying insects arise when you brush by a plant in the garden. Whiteflies are in the same order, Homoptera, as aphids.

Bandedwinged whitefly (Trialeurodes abutilonea)
adult and immatures on leaf

BIOLOGY:

Whiteflies go through four stages of development: egg, larva, pupa and adult. The cycle takes from 2 -3 weeks in warm weather but may take as long as 2 months under cool conditions. The eggs of most species are laid on the under side of the leaves. When the larva hatches out it is mobile (called a crawler) only very briefly then it settles down and begins feeding. Once feeding starts it doesn’t move about anymore. When the larval stage has completed development it becomes a pupa, a quiet, non-feeding stage. The adult emerges, is capable of flying, mates and the female begins laying eggs. Whiteflies spend winters in weeds and ornamentals. Often sources of infestation are infected nursery stock brought in from an area where the whiteflies can easily overwinter. Whitefly adults can be easily carried about on wind currents, though most of their flying is done close to the ground.

CONTROL:

Control of whiteflies can be difficult and pesticides should be chosen with care. Use an integrated pest management program, combining cultural, biological, mechanical and chemical methods, for control. Natural enemies play an important part in the control of the whitefly population. Pesticides, used at the wrong time or improperly, kill the beneficial insects as well and allow for rapid redevelopment of whitefly populations.

Carefully check all newly purchased plants before introducing them into your garden. Look closely at the under side of the leaves to make sure you are not bringing a problem into the garden.

Destroy plants that are heavily infested before the whiteflies can spread. Remove them from the garden and do not compost them. Carefully check weeds for infestations.

Barriers such as floating row covers can be used to keep whiteflies off plants. These covers will have to be removed for proper pollination to take place.

If necessary to use chemicals insecticidal soap will provide control with the least amount of damage to the beneficial insect populations.

Article written by Jack Arnott (former program assistant)

REFERENCES:

USDA Whitefly Knowledgebase, http://www.ifas.ufl.edu/~ent2/wfly/wfly0002.htm

Picture from the United States Department of Agriculture, WHITEFLY KNOWLEDGEBASE

The University of Georgia and Ft. Valley State University, the U.S. Department of Agriculture and counties of the state cooperating. The Cooperative Extension Service offers educational programs, assistance and materials to all people without regard to race, color, national origin, age, sex or disability.

Page last updated 09/00, Arnott