Location: Subtropical Plant Pathology Research2010 Annual Report
1a. Objectives (from AD-416)
To determine and characterize factors associated with the dispersal and development of the whitefly-transmitted viral disease watermelon vine decline, as well as two emerging viral diseases cucurbit leaf crumple and cucurbit yellow stunting disorder, and develop a regional decision support system for managing them.
1b. Approach (from AD-416)
Perform intensive field surveys of commercial cucurbit, tomato, and other vegetable crops in southwest Florida to characterize the temporal and spatial pattern of whiteflies, and identify reservoirs of Squash vein yellowing virus, Cucurbit leaf crumple virus, and Cucurbit yellow stunting disorder virus. Use the spatial information to identify factors that contribute to their increase and determine how they may impact management. Develop the tools necessary to delivery real-time forecasts (decision support system) of virus incidence and whitefly density to the industry. Improve understanding of whitefly transmission of SqVYV by examining the interaction of plant age, time of infection, and virus distribution, and whitefly acquisition and transmission of SqVYV. Specialty Crops Research Initiative.
3. Progress Report
This research relates to inhouse objective 1. Characterize ecology, biology, epidemiology, genetics and host interactions of domestic, exotic, newly emergent and re-emerging pathogens. Whitefly-transmitted SqVYV and CuLCrV have had serious impact on watermelon production in southwest and west-central Florida in the past 5 years. A field study was designed to characterize the spatial and temporal patterns of disease, quantify viral associations, and determine how environmental factors affect epidemic development. The study was conducted over six growing seasons in a 1 ha field of ‘Fiesta’ in Immokalee, FL. It was observed that not all viruses appeared in every growing season, and that certain environmental parameters may be useful in predicting the occurrence of SqVYV. Data also suggest that SqVYV and CuLCrV are being introduced by separate whiteflies, even thought the whiteflies could emigrate from the same field. The data gathered from this study can be used to partially predict epidemic development and test management strategies that ultimately result in better control. Tomato yellow leaf curl virus (TYLCV) has caused millions of dollars of lost production. In collaboration with growers we collected and analyzed insect and disease scouting reports and used regional weather data to determine spatial and temporal features associated with TYLCV epidemics and whitefly densities. The data show that the severity of TYLCV closely follows the increase in mean whitefly density, and that the average numbers of whiteflies in any one field is linearly related to the number of whiteflies in its neighboring fields. There is a positive correlation between wind speed and whitefly density and higher temperatures have a negative impact on both whitefly density and TYLCV. Wintertime minimum temperatures have 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.