Whiteflies are tiny pests that can become big problems for your garden. Not only does their feeding damage your plants, they can also transmit plant viruses. This can add up to headaches for growing tomatoes and other plants. The most common species of this garden pest are the bandedwinged, greenhouse, silverleaf and sweet potato whiteflies. Unfortunately, all these species have somewhat broad host ranges.
What do whiteflies look like?Adult whiteflies resemble tiny moths and are covered with a white waxy powder. They’re rarely more than 1-3 millimeters long and are typically found on the undersides of leaves. Immature forms have a scalelike appearance and are sometimes mistaken as scale insects. Bandedwinged whitefly (Trialeurodes abutilonea) adults have brownish bands across their wings, and their body is gray. Greenhouse whitefly (T. vaporariorum) adults hold their wings flat over their bodies. The pupa has sides that are parallel to each other with hairs covering it. Silverleaf whitefly (Bemisia argentifolii) is a bit smaller and more yellow. Its wings are held rooflike at about a 45-degree angle. The pupa case is more domed-shaped, with a few random hairs. Sweet potato whitefly (B. tabaci) is similar to silverleaf whitefly, with adults holding their wings in a rooflike manner and dome-shaped pupa with few random hairs. What kind of damage do whiteflies cause?Adult female whiteflies insert their eggs into the leaf tissue of a plant. A minute larva in the “crawler” stage hatches out and begins to feed on this leaf tissue by inserting its mouthparts into leaves and sucking sap from the plant tissue. At this stage, the pest is called a scale (not to be confused with a scale insect, which at this stage it resembles greatly). While feeding, a sticky waste substance is excreted by the insect (commonly called honeydew). This liquid adheres to leaves and provides a medium for sooty mold to colonize and grow. Sooty mold is black and eventually covers leaves and stems. This mold inhibits infected portions of the plant from photosynthesizing and also causes aesthetic damage. After growing through several life stages, the larvae finally enter a pupal stage. Here, becoming sexually mature, whiteflies take on the adult form and eventually emerge as winged adults. Infested plants are seemingly chlorotic (turning yellow), causing some plant varieties to have a silvery appearance. Whiteflies also produce honeydew. This sweet, sugary liquid adheres to leaves and promotes a black mold (known commonly as sooty mold) that colonizes and grows on the leaf surface. Sooty mold eventually covers leaves and stems. It inhibits infected portions of the plant from photosynthesizing, as well as causes aesthetic damage. Ants are often present as well – they feed on the sugary honeydew waste droplets.
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