Author
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Turechek, William |
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Submitted to: Symposium Proceedings
Publication Type: Proceedings Publication Acceptance Date: 8/1/2010 Publication Date: 9/8/2010 Citation: Turechek, W. 2010. Environmental and geographical variables associated with TYLCV epidemics in southwest Florida. Symposium Proceedings. 15-16. Interpretive Summary: Tomato yellow leaf curl virus (TYLCV) was first detected in south Florida in 1997. The virus, which is vectored by the silverleaf whitefly, has spread widely in Florida resulting in millions of dollars of lost production. Understanding of the temporal and spatial features associated with TYLCV epidemics will help with efforts to design and test new management options. For example, by identifying local “hot spots” surveys can be designed to identify possible reservoir hosts and/or crops for the virus and may also be helpful in identifying pockets of insecticide-resistant whiteflies. In collaboration with growers and industry representatives we have collected and analyzed data obtained from insect and disease scouting reports and used regional weather data to determine the temporal and spatial features associated with TYLCV epidemics and whitefly densities in vegetable production fields in southwest Florida. The data show that the severity of TYLCV closely follows the increase in mean whitefly density, as well as the average age of the fields in production. There is a linear relationship between the average numbers of whiteflies in neighboring fields, i.e., fields that share a common boundary, and in fields that are located two and three fields over, although the strength of the relationship decreases with distance. There is a positive correlation between wind speed and whitefly density and higher temperatures have a negative impact on both whitefly density and TYLCV. However, because of the strong correlation between whitefly density and TYLCV severity, it is difficult to determine whether the impact of temperature is directly affecting whiteflies, disease development, or both. Wintertime minimum temperature, particularly the number and duration of sub-freezing events, has an impact on both whitefly populations and virus incidence. The results of the analyses argue for a greater regional effort in managing whiteflies and TYLCV and we are developing a decision support system for management and tracking whiteflies and virus across commodities to help achieve this goal. Technical Abstract: Tomato yellow leaf curl virus (TYLCV), which is vectored by the silverleaf whitefly (Bemisia tabaci biotype B), was first detected in south Florida in 1997. The virus has spread widely in Florida and is responsible for millions of dollars of lost production. A more complete understanding of the temporal and spatial (geographical) features associated with TYLCV epidemics may help with efforts to design and test new management options. For example, by identifying local “hot spots” surveys can be designed to identify reservoir hosts and/or crops for the virus and may also be helpful in identifying pockets of insecticide-resistant whiteflies. In collaboration with growers and industry representatives we receive scouting reports for approximately 17,000-20,000 acres of tomato and vegetable production in southwest Florida so that we can map and analyze the spatial and temporal patterns of TYLCV epidemics and whitefly densities in production fields to gain an understanding of how epidemics develop. Regional weather data are collected to measure the correlations between various climatic variables, TYLCV incidence, and whitefly densities. The data show that the severity of TYLCV closely follows the increase in mean whitefly density, as well as the average age of the fields in production. There is a linear relationship between the average numbers of whiteflies in neighboring fields, i.e., fields that share a common boundary, and this relationship extends to fields that are located two and three fields over, although the strength of the relationship decreases with distance. Certain climatic variables appear to impact disease and its vector as well. The most consistent relationship is the positive correlation between wind speed and whitefly density. Temperature has a negative impact on both whitefly density and TYLCV, meaning that hotter temperatures are less conducive to epidemic development. However, because of the strong correlation between whitefly density and TYLCV severity, it is difficult to determine whether the impact of temperature is directly affecting whiteflies, disease development, or both. Wintertime minimum temperature, particularly the number and duration of sub-freezing events, has an impact on both whitefly populations and virus incidence. In some years, precipitation has a small negative correlation on whitefly density and others years it has had no noticeable effect. The results of the analyses argue for a greater regional effort in managing whiteflies and TYLCV and we are developing a decision support system for management and tracking whiteflies and virus across commodities to help achieve this goal. |
