Whitefly

Often confused with aphids, these insects feed on the underside of leaves. They can reduce plant vigor and cause a number of plant disorders and viruses. They reproduce quickly and spread at a rapid rate. Whiteflies have an extremely wide host range, including poinsettia, peppers, tomato, mustard, cabbage, cucumber, bush beans, and soybeans.

Our beneficial insect and organism solutions will control whitefly infestations. Both adult and nymph stages feed by sucking the plant juices. Large populations or heavy feeding by whitefly can give plants a mottled look, cause yellowing and eventually death to the host plant.

Adult whitefly are tiny, white, waxy winged insects that leave plants as soon as they are disturbed. They stay close together and often gather at the top of the plant. Whitefly are often confused with aphids, which shed and leave their skin behind on the leaves. To differentiate between the two, shake the plant. The whitefly will fly off the plant, whereas the aphid skins will remain motionless. A number of whitefly infestations originate from plants brought into the greenhouse. For this reason careful inspection is crucial. In addition, adult whiteflies can survive winters if temperatures do not fall below freezing. Finally, whiteflies may also enter a greenhouse through vents if they are not properly sealed.

Female whiteflies are capable of laying up to 200 eggs. Eggs can be found in groups on the underside of the leaves. Small larvae will emerge and search out feeding sites on the underside of the leaves. Once they settle down they will lose the ability to move. This immobile "scale" stage is pale green, about 2mm long and lives on the underside of the lower leaves only. The life cycle consists of adults laying eggs, to larvae, to scale and finally to adult. This whole process can be completed in 3 weeks in the summer.

In December, 2004, a newly introduced strain of silverleaf whitefly – Biotype Q – was identified in California and Arizona. It has since been identified in Georgia, Michigan, New York, and Oregon. It was originally found in Poinsettia and cotton. It is thought to have come into the US from Spain, where it is a continuing problem. Its physical appearance is identical to Biotype B, but it is better at building lasting resistance to pesticides than Biotype B. Therefore, it is important to use natural controls like the fungus Beauvaria bassiana (Mycotrol O) and to use beneficial insects if you believe you have this new problem.