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A series of experiments has been conducted aimed at learning more about whitefly biology. We learned that: 1) whitefly eggs imbibe water from plant tissue; 2) the wax particles on exterior body surfaces may be antifungal; 3) mature lettuce is not a good host for whiteflies and; 4) there is a migrating morph. All these facts are of practical importance.

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A survey study was undertaken to identify the plant viruses, to document the occurrence of virus diseases, and to document the seasonal population dynamics of insect vectors in a semi-isolated agricultural site in Central Arizona. A typical year-round cropping history at the site consists of cotton and seasonal sequences of vegetables. The most abundant insects caught using 24-hr exposures of yellow sticky traps were whiteflies (Trialeurodes abutilonea Haldeman and Bemisia tabaci Genn.) and the cotton (or melon) aphid (Aphis gossypii Glover). Of the three, only B. tabaci and A. gossvpii are recognized as virus vectors in Arizona. The most prevalent plant virus identified in vegetable crops and/or weeds was lettuce infectious yellows virus (LIYV), a whitefly-transmitted virus. The virus was detected in lettuce, (greenleaf, romaine, iceberg, red leaf) watermelon, cantaloupe, spinach, and cilantro. In addition, the watermelon curly mottle/squash leaf curl virus complex (WCMoV-SLCV), watermelon mosaic virus 2 (WMV-2) zucchini yellow mosaic virus (ZYMV), cucumber mosaic virus (CMV), and squash mosaic virus (SqMV) were identified in cucurbits at various times and locations throughout the season.

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Geographic Information Systems (GIS) are computer databases that organize information in a spatial framework. This allows the analysis of data based in part on location. A pilot project has been set up in the Yuma Valley to explore the use of GIS to study the influence of crop sequences, weeds, urban areas, and insect vector populations on the incidence of virus diseases of vegetables. The goal is to learn to collect field observations in such a way that long term regional trends can be understood and visualized. Such information can then be used in management plans.