Common Name: Silverleaf whitefly
Scientific Name: Bemisia argentifolii Bellows & Perring
Description: The sweetpotato/silverleaf whitefly adult is small, about 0.9 to 1.2 mm in length and holds its solid white wings roof-like over a pale yellow body while at rest. Immature stages begin with a pointed oblong yellow egg (0.2 mm) which darkens at the apex just before hatching. The first instar or crawler stage (0.2 – 0.3 mm) settles down on the underside of leaves and goes through three more molts as a sessile, flattened yellow oval nymph. The last instar is often referred to as a pupa (0.7 – 0.8 mm) and has distinct eye spots. A number of other whitefly species are important plant pests in Texas.
Life Cycle: Intermediate. The number of eggs produced is greater in warm weather, but typically range from 50 to 400 eggs (avg. 160, of which about 2/3 are female) per female. Eggs hatch into active, wingless, crawler stages which soon settle into the sessile, scale-like second larval stage (instar). This stage molts into a third larval stage which and then becomes the pupa from which the adult emerges. The molt from the third larval stage to the pupa occurs internally and wings develop inside the puparium. The duration from egg to adult may be 18 days under warm temperatures, but may take as long as 2 months under cool conditions.
Habitat and Food Source(s): Direct crop damage occurs when whiteflies feed on plant phloem in high enough numbers, excreting honeydew which promotes sooty mold and reduces plant quality. Chlorosis of leaves and/or bleaching of parts of poinsettia plants has been associated with whitefly infestation. Sweetpotato/silverleaf whitefly adults often concentrate on younger leaves where oviposition is highest. Following the development of the plant, larger nymphs are typically more numerous on older leaves.
Direct observation and use of yellow sticky traps are useful methods for monitoring whiteflies. The most valuable stage for taxonomic purposes is the empty pupal skin which can be collected by picking infested leaves and storing them in envelopes.
Pest Status: Immature stages can infest and injure a large number of host plants, occasionally transmitting plant diseases; has become a widespread difficult-to-control pest of Texas greenhouse and nursery crops since 1987 particularly on cotton, vegetables and ornamental plants such as poinsettia and hibiscus; medically harmless.
Literature: Borror et al. 1989; Drees 1994.