Nymphs and adults suck plant juices from citrus, greenhouse foliage plants, ornamentals, and vegetables. Their feeding weakens plants; they also secrete a sticky, sugary substance called honeydew. Sooty mold, a black fungus, grows on the honeydew-coated leaves and fruit. Whitefly feeding can also spread viral diseases.
Females lay eggs on undersides of leaves; these hatch in 2 days into tiny, mobile scales; while continuing to feed on plant juices, scales molt to a legless stage in a few days. After several growth stages, nymphs rest in a sort of pupal stage before emerging as adults. Most whitefly species require 20 to 30 days for a complete life cycle at room temperature, fewer in summer. Numerous overlapping generations per year, continuing all winter in greenhouses and warm climates. In cold-winter areas, whiteflies may infest plants outdoors during warm summer weather; cold weather will kill them off.
Catch adults on yellow sticky traps; vacuum adults from leaves; remove infested leaves; indoors, release Encarsia formosa parasitic wasps to control greenhouse whitefly; outdoors, attract native parasitic wasps and predatory beetles; spray with insecticidal soap or garlic oil; as a last resort, spray with pyrethrin.
Photo: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org