Preliminary Investigation of Sweet Potato Whitefly Population Dynamics Across Arizona

The sweet potato whitefly can have an impact on cotton by reducing yields through direct feeding damage, by transmitting the cotton crumple leaf virus during feeding and by the production of large amounts of sticky honeydew that interferes with the harvesting and ginning process. Data on whitefly populations collected weekly from 938 yellow sticky traps near cotton fields have been entered into a geographic information system (GIS) database. In general, whitefly populations were high near cotton fields in the Yuma area before July 6th. They rose rapidly in central Arizona between July 6th and July 20th. During the month of August, counts continued to rise in central Arizona, particularly in western Pinal County. Populations began to fall during October. Whitefly populations in eastern La Paz County were slower to develop than in other areas in western Arizona. Whitefly populations in Graham and Cochise County were not significant throughout the growing season. Cotton crumple leaf virus was observed in parts of central and western Arizona. Introduction In recent years the sweet potato whitefly has had a significant impact on Arizona agriculture. Damage associated with the sweet potato whitefly has been well documented (Byrne et al. 1990, Johnson et al. 1993). Whiteflies cause reduced yield due to 1) extraction of phloem sap, 2) contamination of plant material by sooty mold fungi (Capnodium spp.), 3) interference with harvesting and ginning because of honeydew contaminated fibers, and finally, 4) reduced yields due to the cotton crumple leaf virus (Brown, Mihail and Nelson 1987). In the past, we have not had a broad overview of whitefly population dynamics statewide. The collection of these data will allow us to make statements in the future about the statewide dynamics in whitefly populations and how they relate to changes in climate and cropping patterns. Observations on cotton crumple leaf virus will allow us to assess the impact of this disease in relation to the timing of the whitefly population buildup. I Department of Plant Pathology, University of Arizona, Tucson. 2 Department of Entomology, University of Arizona, Tucson. 3 Southwest Boll Weevil Program, Tempe. 4 Arizona Cotton Research and Protection Council, Tempe. 5 USDA, APHIS, Phoenix. 6 The authors would like to acknowledge the contributions of the staff at the Southwest Boll Weevil Program for providing, deploying, and collecting the traps. We would like to thank Barbara Boron and Shirley Haller for counting the whiteflies on the traps and entering the trap data into the computer database.