Several species of whitefly occasionally infest grapes.
Overwintering whitefly are relatively rare in B.C. Some sub-tropical and tropical species, such as the common greenhouse whitefly (Trialeurodes vaporariorum (Westwood)), infest outdoor plants each season from infested greenhouses, house plants and vegetable and ornamental transplants.
Adults are small, around 2 mm in length, with two pairs of wings that are covered with a fine, white powder. They somewhat resemble small white moths.
The minute crawlers are mobile for only a few hours until they settle and develop into nearly translucent, scale-like immobile nymphs.
The scales have a fringe of waxy material projecting from the bottom edge. The distribution and numbers of the projections can assist in species identification.
The pupal stage that develops inside the case on the underside of leaves is somewhat bulbous and appears segmented. There are several generations per year.
Whitefly feed by sucking juices from the leaves, much as scale insects do, and they also produce large amounts of sugary honeydew.
Populations are controlled by parasitic Encarsia wasps that turn the scales black as well as by several predatory insects and pathogenic fungi.
