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Project description

Biological Control of Whiteflies on Poinsettia: Evaluation of Parasites. (90BC043)
Program UC IPM competitive research grants program
M.P. Parrella, Entomology, UC Davis
O. Minkenberg, Entomology, UC Davis
K.M. Heinz, Entomology, UC Davis
Host/habitat Flowers; Poinsettias; Greenhouse Crops
Pest Sweetpotato Whitefly Bemisia tabaci; Greenhouse Whitefly Trialeurodes vaporariorum
Discipline Entomology
Biological Controls
Start year (duration)  1990 (Three Years)
Objectives Development and implementation of biological control of the sweetpotato whitefly, Bemisia tabaci Gennadius, and the greenhouse whitefly, Trialeurodes vaporariorum (Westwood), on greenhouse poinsettia.

Due to explosive outbreaks of B. tabaci in greenhouse and field production areas in California, and because California growers are reporting almost no problems resulting from outbreaks of T. vaporariorum, we have focused on the development and implementation of an efficient biological control program for B. tabaci.

The greenhouse and sweetpotato whiteflies are currently the most important pests attacking poinsettia in California. The commercially available parasite, Encarsia formosa, is able to control the greenhouse whitefly in commercial poinsettia production but not the sweetpotato whitefly. As a result, we have initiated a search for parasites with the ability to control the sweetpotato whitefly on poinsettia when used in inundative or inoculative releases. This research may have applicability to many other crops where the sweetpotato whitefly is a major problem.

Colonies of two other Encarsia spp., E. tabacivora and E. deserti, have been initiated at UC Davis and comparative biological studies are underway. An important part of the evaluation procedure is to try and identify parasites with the capability of locating whitefly foci in the greenhouse when population levels are low. To accomplish this, a parasite may use chemical queues for orientation. A four-armed airflow olfactometer has been constructed to ascertain whether the parasites can respond to different odor fields. These studies have just been initiated.

Research with the olfactometer can provide important information concerning parasite behavior, but these data cannot stand alone and must be combined with direct and indirect observations of parasite biology and behavior. Direct observations have been made to determine searching time, host feeding, host rejection, oviposition, and whether a parasite can distinguish between infested and noninfested leaves. Indirect observations have been used to assess parasite longevity and functional response. Data have been collected in all these areas, but are too preliminary to make any comparisons between parasites. In addition, other parasite colonies will be started soon (including E. Formosa and other non-Encarsia spp.) and similar studies are planned.

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