Silverleaf Whitefly

FACTS, IDENTIFICATION & CONTROL  LATIN NAME Bemisia argentifolii APPEARANCE

Adult silverleaf whiteflies are tiny – typically 1.5 mm in length. They are yellow with tilted white wings on top of their bodies. Males are slightly smaller than females. Eggs are pear-shaped and approximately 0.2 mm in length. Pupae are oval-shaped and about 0.7 mm in length with dorsal bristles called setae.

BEHAVIOR, DIET & HABITS

Silverleaf whitefly populations feed on various plants, particularly the undersides of leaves. They are also known to feed on crops, such as tomato, eggplant, cucumber and squash. They damage these crops by injecting a toxin while feeding, producing honeydew and even by transmitting one of several Gemini viruses.

The silverleaf whitefly is primarily found in California deserts – the Imperial, Palo Verde, Coachella and San Joaquin valleys – but also can be found in Arizona, Texas and Florida. They are a major pest in most irrigated agricultural areas. The actual origins are unknown, but the silverleaf whitefly is thought to be native to India. 

REPRODUCTION

Silverleaf whiteflies go through four nymphal stages before reaching maturity. During the first stage (or instar), eggs begin to hatch and are flattened, about 0.3 mm in length and greenish-yellow in color. Shortly after hatching, nymphs are able to crawl a short distance. Second and third instar nymphs are oval-shaped and begin to look like tiny insects. They have no distinguishing features but start to suck sap from plants at this stage. Once in the fourth instar, red eyes appear, yellow bodies become visible and the nymphs range from 0.6 to 0.8 mm in length.

In warmer climates, a typical life cycle lasts 18 to 28 days, but they can last up to 48 days in the winter. Adults generally emerge in the morning, males coming first. Their emergence depends on the temperature. It takes around four hours before adults can begin to fly and around 10 to 20 hours before females and males begin to mate. Their populations increase in spring and summer. The whitefly can complete 8 to 12 generations in one year.

SIGNS OF A SILVERLEAF WHITEFLY INFESTATION

Common signs of an infestation include spots on leaves caused by feeding, leaf curling, yellow veining, leaves covered in honeydew, tiny yellow and white scales, white streaks, uneven ripening of vegetables and reduced plant or crop growth. Leaves may show fungal growth or abnormal colors or patterns. 

ADDITIONAL INFORMATION

Whitefly infestations often are kept in check by beneficial insects. If populations reach high numbers, treatment in the fall is preferable. It is important to control populations before they reach large numbers or else it greatly increases the difficulty of control. Among the most common control methods are the management of weeds, cleanup of crop residue and use of chemical controls. The use of sticky traps also has proven successful. Placing three to five traps on crops can attract whiteflies and provide a warning of their presence before their population increases.