Location: Subtropical Plant Pathology Research2011 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 project is related to inhouse objective 1: Characterize ecology, biology, epidemiology, genetics and host interactions of domestic, exotic, newly emergent and re-emerging pathogens. The intent of this study is to develop strategies for managing Squash vein yellowing virus (SqVYV)-induced watermelon vine decline and diseases caused by other whitefly-transmitted viruses of vegetables in Florida and the Southeast. This report summarizes results for objectives to: 1) Characterize patterns of viral epidemics and whitefly densities in production fields and their surroundings to gain an understanding of epidemic dynamics and identify “hot spots” and reservoir crops for both whitefly and viruses; and 2) Development of a decision support system to deliver recommendations for managing whiteflies and virus. Tissue blot hybridization assays were developed for rapid diagnosis of SqVYV, Cucurbit leaf crumple virus, Cucurbit stunting disorder virus, and Papaya ringspot virus. Assays were used to determine the within-plant distribution of these four viruses in watermelon plants with single or mixed infections. We are currently evaluating the sensitivity and specificity of the hybridization assay for its ability to detect SqVYV and comparing it to the performance of reverse-transcriptase (RT-) polymerase chain reaction (PCR). Characterization of these parameters will allow us to better interpret epidemiological data based on the hybridization assay and RT-PCR tests. In collaboration with growers we continue to collect and analyze insect and disease scouting reports to determine spatial and temporal patterns associated with Tomato yellow leaf curl virus (TYLCV) epidemics and whitefly densities. The data continue to 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 related to the number in neighboring fields. The spatial analyses of the data argue for a greater regional effort in tracking and managing whiteflies and TYLCV and we are developing a decision support system to be used across commodities to help achieve this goal. We have developed a smartphone application that will allow growers and scouts to enter global positioning system (GPS)-labeled disease, insect, and production information directly into their smartphone where it will be saved and uploaded to a central server. The system will also allow scouts to develop field-specific, pest management recommendations that can be delivered directly to growers on their smartphone. It is believed that this system will enable growers to manage pests on regional (versus individual) scale ultimately reducing pest and disease pressure within the region.