Author
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CANAS, L. - UNIV OF AZ DEPT. OF ENTOM |
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Naranjo, Steven |
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ELLSWORTH, P - UNIV OF AZ DEPT. OF ENTOM |
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Submitted to: Sweetpotato Whitefly Progress Review Proceedings
Publication Type: Proceedings Publication Acceptance Date: 4/1/2002 Publication Date: 6/1/2002 Citation: N/A Interpretive Summary: Technical Abstract: The current ongoing study has examined seasonality and mortality patterns of B. tabaci on different hosts during the year. Plots of six representative host plants (broccoli, cantaloupe, cotton, alfalfa, Lantana and various weeds) were established at the Yuma, Maricopa and Marana Agricultural Centers in Arizona. These sites represent the range of geographic and climatic areas of the state for cotton production. Here we report findings from the first year of the study. Two host plants, cantaloupe and Lantana, were observed to provide a good environment for the buildup of B. tabaci populations during the fall. B. tabaci populations declined steadily with decreasing temperatures during the winter. Low temperatures affected the host plants, with Lantana plants losing all foliage due to freezing temperatures. However, a significant number of Lantana plants produced new foliage during the spring and summer. After the decline during the winter, populations survived in broccoli and Malva parviflora (cheeseweed), and built up in broccoli, cantaloupe and Lantana. Populations of B. tabaci were extremely high in Lantana and cantaloupe, which allowed for significant densities in cotton once this crop was established. In addition, during the middle of the summer, ground cherry plants hosted large densities of B. tabaci. The prevalence of different weed species through the year also allowed for increased populations. From the three different regions, Yuma showed earlier increases in B. tabaci populations, followed by Maricopa and Marana. Yuma populations were in general smaller than those of Maricopa and Marana. B. tabaci populations in alfalfa were low at all sites. Life table analyses demonstrated differences in survivorship patterns on the different hosts. In general, the highest survivorship was observed in cantaloupe at all sites. The highest B. tabaci survival at Marana occurred in cantaloupe (about 47%) followed by Lantana (15%), weeds (15%) cotton (4%), alfalfa (3%) and broccoli (2%). Yuma had the highest survival in cantaloupe (45%) followed by broccoli (31%), Lantana (19%), weeds (17%) and cotton (7%). Maricopa had the highest survival in cantaloupe (45%) followed by broccoli (45%), Lantana (33%), alfalfa (28%), weeds (15%) and cotton (4%). From the different mortality factors observed, both predation and dislodgment accounted for a significant portion of the mortality at all locations. Dislodgment and desiccation were important in some host plants and probably were influenced by low temperatures. For instance, broccoli cohorts suffered high mortality due to desiccation and dislodgment. Rates of predation were relatively high in all host plants but more so in cotton across the different locations. Parasitism by Encarsia and Eretmocerus varied from host to host and from location to location. Parasitism was highest in Lantana, especially at Maricopa (32%). Despite high levels of B. tabaci mortality at the three locations, it was insufficient to prevent population outbreaks in most plant hosts. The examination of the biodemographic characteristics of B. tabaci during the year, especially during the winter months will provide important information relative to the cold hardiness and survival of this species. Such information will aid the prediction, and possibly the prevention, of outbreak populations in the late spring and summer |
