Garden Pest: Whiteflies

Family Aleyrodidae

DESCRIPTION

• Adults
  Minute sucking insects with powdery white wings; whiteflies rest in huge numbers on leaf undersides and fly out in clouds when disturbed.
• Larvae
  Flattened, legless, translucent, 1/30-inch scales on leaf undersides.
• Eggs
  Gray or yellow cones the size of a pinpoint.
• Commonly found in greenhouses throughout North America; also found outdoors in warm regions of California, Florida, and Gulf states, and areas on the West Coast.

DAMAGE
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.

LIFE CYCLE
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.

CONTROL
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. 

Keep reading: Make your own organic pest control spay with hot peppers and garlic

Photo: Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org