Progress 09/01/08 to 08/31/13
Outputs
Target Audience: The Florida commercial tomato and vegetable industries, the scouting companies hired to scout production fields, and Extension are the primary beneficiaries of this work. However, the research on whiteflies and the viruses they transmit has applicability to other annual vegetable cropping systems that deal with whitefly-vectored viruses. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest? Results to stakeholders have primarily been disseminated as talks or lectures at commodity and/or industry group meetings, which are often supplemented by proceeding or summary articles. We have also held several online training sessions over the course of the study to teach potential users of AgScouter how to use AgScouter. These meeting were generally hosted by ZedX Inc. Also, there have been popular press articles published with respect to AgScouter. Finally, several peer-reviewed manuscripts have been published as part of this work, and there are several additional publications that will result from this work in preparation. What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
The Southeastern states accounts for nearly half of the production value of US watermelon and fresh market tomato. But in the past decade, Squash vein yellowing virus (SqVYV)-induced watermelon vine decline (WVD), Tomato yellow leaf curl virus (TYLCV) and other whitefly-transmitted viral diseases have resulted in millions of dollars in lost revenue. The goal of this project was to develop strategies to better control whitefly-transmitted viruses of vegetable crops in the Southeast. Accomplishments from this grant include: (a) the release of 392291-VDR, a watermelon germplasm line with resistance to SqVYV-caused WVD. Since its release, most major U.S. and several international seed companies, along with several University breeding programs have requested and were provided with seed of 392291-VDR. Additional seed are available for distribution to interested research personnel and plant breeders and have also been submitted to the National Plant Germplasm System where they will be available for research purposes, including the development and commercialization of new cultivars. (b) The development of the AgScouter system for collecting and viewing scouting data using GPS capable mobile devices. AgScouter is slated to be commercially available in 2014 and will be marketed by ZedX Inc. to specialty crop growers across the United States. Based on past sales of related products, it is anticipated that AgScouter will serve a customer base of 5000 growers producing on over 1 million acres. (c) The development of two new diagnostic tests for SqVYV which have become the current standard for testing samples for SqVYV infection and, to date, have been used on over 4000 cucurbit samples from FL, CA, GA, SC, IN, and Puerto Rico. SqVYV was detected in all locations except CA. (d) A better understanding of whitefly biology, particularly in the areas of insect management and virus transmission. Impacts of improved scouting methods for whitefly and viruses include more targeted and fewer pesticide applications, resulting in delayed development of insecticide resistance and preservation of both wild and managed insect pollinators. (e) A detailed characterization of the spatial and temporal patterns of infection caused by SqVYV, Cucurbit leaf crumple virus (CuLCrV), and TYLCV. One of the most significant findings was that it was shown that the severity of TYLCV closely followed the increase in mean whitefly density and that a “hot field” can affect fields within a 1.5 to 3.0 mile radius. The following reports additional detail the accomplishments by order of the objectives listed above. (1) Several studies were conducted to develop field-based strategies for managing WVD. First, the use of silver plastic mulch and insecticide on the development of WVD was investigated in field plots of watermelon. Results showed that reducing whitefly populations with insecticides significantly limited WVD, but the use of silver plastic mulch produced mixed results. A second study was completed that showed that the use of SqVYV-resistant pollenizers could significantly reduce WVD. As a result, 392291-VDR, a watermelon germplasm line with resistance to SqVYV was released. A third study was performed to evaluate the utility of adding an insecticide (endosulfan) to the end-of-the-season burndown herbicide treatment (Gramoxone) as a means to limit the migration of whiteflies to neighboring crops. Results were inconclusive in a tomato trial; however, in watermelon, plots treated with the combination of insecticide and herbicide had the lowest whitefly migration relative to plots treated with Gramoxone alone. (2) In order to develop sampling methods for whiteflies on watermelon, the distribution of immature and adult whitefly within watermelon plants was monitored in a field experiment conducted over two growing seasons. A stratified distribution of different life stages within the plant was found. Eggs and adult whiteflies were found on the youngest third of the vine with the highest means and lowest variation found on the 5th through 9th leaves from the tip of the runner. First and second instar nymphs were grouped in the middle third of the plant, with older nymphs on the oldest part of the vine. This information is being used to develop a sampling plan for whiteflies. SqVYV is often found in mixed infections with the aphid-transmitted potyvirus Papaya ringspot virus type W (PRSV-W). Whitefly transmission of SqVYV in single infections has been characterized, but transmission in mixed infections with potyviruses has not. When plants were simultaneously inoculated with both viruses, subsequent transmission of SqVYV by whiteflies was dramatically reduced. This also occurred if plants were inoculated with PRSV-W one week before inoculation with SqVYV. The highest rates of transmission were from plants inoculated five to eight days earlier, but a low level of transmission occurred as early as two days post inoculation. (3) The spatial and temporal patterns of mixed infections of SqVYV, CuLCrV, and Cucurbit yellow stunting disorder virus (CYSDV) was studied. Results showed that SqVYV was the dominant virus in the system and its presence impacted the development of both CuLCrV and CYSDV. SqVYV and CuLCrV progressed in a logistic fashion and had similar rates of disease progress. All viruses displayed significant but variable levels of aggregation in the field. A positive correlation between mean disease incidence and mean number of whiteflies was found, and an analysis of their association indicated that the viruses were largely transmitted independently. In a second study, the epidemiology of TYLCV in southwest Florida was characterized. Data of virus incidence and whitefly densities was obtained from scouting reports from cooperating growers from 2006-2013 covering nearly 24,000 acres of tomato and was used to track and identify regional hot spots of whitefly and virus and to identify geographical and/or management practices linked to TYLCV epidemics. The data showed that the severity of TYLCV closely followed mean whitefly density and the average age of the fields in production, and that a “hot field” can affect fields within a 1.5 to 3.0 mile radius. Moreover, spatial analysis of the surveyed region showed the existence of hot spots for both whiteflies and virus but they were not associated with any single grower or management practice. Climatic conditions are currently being analyzed to determine their role in epidemic development; results have not been finalized at the time of this final report. (4) The AgScouter system for collecting and viewing scouting data using GPS capable smartphones or tablet computers was developed. AgScouter users utilize a mobile device to collect and upload GPS-labeled scouting data to a central server. Data can be processed and then delivered as real-time reports. The initial impetus for AgScouter was the realization that both insect vectors and the viruses they transmit respond to stimuli (climatic, geographical, etc.) that occur at scales significantly larger than what a typical farm operation has control over. Hence, management of these pests likely requires a coordinated, regional effort from the grower community to which AgScouter is intended to facilitate. To make it widely adaptable, AgScouter was developed to be used for a wide variety of crops. Further modifications and testing of AgScouter continues in response to user input and emerging technology.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Adkins, S., McCollum, T.G., Albano, J.P., Kousik, C.S., Baker, C.A., Webster, C.G., Roberts, P.D., Webb, S.E., and Turechek, W.W. 2013. Physiological effects of Squash vein yellowing virus infection on watermelon. Plant Disease 97:1137-1148.
- Type:
Journal Articles
Status:
Published
Year Published:
2011
Citation:
Adkins, S., Webster, C.G., Kousik, C.S., Webb, S.E., Roberts, P.D., Stansly, P.A., and Turechek, W.W. 2011. Ecology and management of whitefly-transmitted viruses of vegetable crops in Florida. Virus Research 159:110-114.
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Kousik, C.S., Adkins, S., Turechek, W.W., Webster, C.G., and Roberts, P.D. 2012. 392291-VDR, A watermelon germplasm line with resistance to Squash vein yellowing virus-caused watermelon vine decline. HortScience 47(12):1805-1807.
- Type:
Journal Articles
Status:
Published
Year Published:
2012
Citation:
Kousik, C.S., Adkins, S., Turechek, W.W., Webster, C.G., Webb, S.E., Baker, C.A., Stansly, P.A., and Roberts, P.D. 2012. Progress and challenges in managing watermelon vine decline caused by whitefly-transmitted Squash vein yellowing virus. Israeli Journal of Plant Science 60:435-445.
- Type:
Conference Papers and Presentations
Status:
Published
Year Published:
2013
Citation:
Turechek, W., Kim, J., Webster, C., Russo, J., Mellinger, H.C., Frantz, G., Lucas, L., McAvoy, E., and Adkins, S. 2013. Further insights into the epidemiology and monitoring practices of tomato viruses. Proceedings of the Florida Tomato Institute, Sept. 4, 2013, Naples, FL. pp 15-16. (Proceedings).
- Type:
Other
Status:
Published
Year Published:
2012
Citation:
Adkins, S., Webster, C.G., Hassell, R., Turechek, W., and Kousik C.S. 2012. Evaluation of virus resistant rootstocks to manage watermelon vine decline and diseases caused by other potyviruses. Vineline Magazine. Fall:41. (Popular publication).
- Type:
Journal Articles
Status:
Accepted
Year Published:
2014
Citation:
Turechek, W.W., Roberts, P.D., Stansly, P.A., Webster, C.G., Kousik, C.S., and Adkins, S. 2014. Spatial and temporal analysis of SqVYV, CuLCrV, and CYSDV in an experimental plot of watermelon. Plant Disease.
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Turechek, W.W., Webster, C.G., Duan, J., Kousik, C.G., and Adkins, S. 2013. The use of latent class analysis to estimate the sensitivities and specificities of diagnostic tests for Squash vein yellowing virus in cucurbit species. Phytopathology 103:1243-1251.
- Type:
Journal Articles
Status:
Accepted
Year Published:
2013
Citation:
Webster, C.G., Kousik, C.S., Turechek, W.W., Webb, S.E., Roberts, P.D., and Adkins, S. 2013. Squash vein yellowing virus infection of vining cucurbits and the vine decline response. Plant Disease 97:1149-1157
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Progress 09/01/11 to 08/31/12
Outputs
OUTPUTS: The overall goal of this project is to develop sound strategies for managing whitefly-transmitted viruses of vegetables, with emphases placed on Squash vein yellowing virus of watermelon and Tomato yellow leaf curl virus in tomato. We continue to receive scouting reports from cooperating growers and through our industry partners Glades Crop Care and Red Gator Consulting for commercial tomato and vegetable production. The data are mapped and analyzed and used to identify environmental, geographical and/or management practices that may be linked to TYLCV epidemics as well as to identify alternate hosts that may exist in neighboring fallow fields, hedge rows, or unmanaged fields and forests. Ongoing spatial analyses continue to indicate the need for a regional effort for managing whiteflies and TYLCV is needed. The Ag Tech company ZedX Inc. was hired to develop a web-based and smartphone technology platform for collection, analysis, and delivery of scouting information. The system was recently named AgScouter. We continue to work closely with scouts and ZedX to optimize the platform for greatest ease of use. Improvements to AgScouter are field tested on a commercial scale by Glades Crop Care. Progress in the development of AgScouter was presented at the annual Florida Tomato Institute meeting in Naples, FL on September 5, 2012. Last year, we reported on the development of two new diagnostic tests for SqVYV: a tissue blot (TB) hybridization assay and a reverse-transcriptase polymerase chain reaction (RT-PCR). For the current reporting year, we evaluated these two tests along with the visual assessment of symptoms as diagnostics for SqVYV infection. We further determined whether their performances varied by the type of plant tissue being tested (crown versus vine tissue), where samples were taken relative to the position of the plant crown, genus, and habitat (field-grown versus greenhouse-grown plants). Results showed that RT-PCR had the highest sensitivity (0.94) and specificity (0.98) of the three tests. TB had better sensitivity than symptoms for detection of SqVYV infection (0.70 vs. 0.32), while the visual assessment of symptoms was more specific than TB and thus a better indicator of non-infection (0.98 vs. 0.65). With respect to the grouping variables, RT-PCR and TB had better sensitivity but poorer specificity for diagnosing SqVYV infection in crown tissue than it did in vine tissue, whereas symptoms had very poor sensitivity but excellent specificity in both tissues. Test performance also varied with habitat and genus, but not with distance from the crown. The results given here provide quantitative measurements of test performance for a range of conditions, and provide the information needed to interpret test results when tests are used singly or in combination for a diagnosis. In a separate study, SqVYV isolates collected from cultivated and weedy cucurbits representing major hosts and locations were analyzed to better understand pathogen diversity and population structure. Little diversity was observed across multiple years of sampling validating ongoing resistance breeding efforts. PARTICIPANTS: William Turechek (lead PI) continued directing the overall project. He performed the statistical analysis described in the evaluation of the diagnostic tests for SqVYY. He also worked closely with personnel at ZedX Inc. to continue to develop AgScouter. Scott Adkins (co-PI) and Craig Webster (postdoctoral associate) did the laboratory work and complied data for the diagnostic performance testing experiment. Also, they led the project to study the diversity of SqVYV. We hired ZedX Inc. as industry collaborator to develop the decision support system named AgScouter. personell TARGET AUDIENCES: The Florida commercial tomato industry and the scouting companies hired to scout production fields are the primary beneficiaries of this work. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The early developments in AgScouter were introduced at the 2010 and 2011 Florida Tomato Institute meetings. AgSouter was recently featured in the August 2012 Edition of Citrus and Vegetable magazine. With these recent promotions we have gotten several requests to develop AgScouter in other systems and geographical areas of the country, particularly California vegetable and grape production. We applied for and have been successful in obtaining additional funding to further develop AgScouter.
Publications
- Webb, S.E., Adkins, S., and Reitz., S.R. 2012. Semipersistent whitefly transmission of Squash vein yellowing virus, causal agent of viral watermelon vine decline. Plant Disease 96:839-844.
- Webster, C.G., and Adkins, S. 2012. Low genetic diversity of Squash vein yellowing virus in wild and cultivated cucurbits in the U.S. suggests a recent introduction. Virus Research 163:520-527.
- Webster, C., Turechek, W.W., Mellinger, C., Frantz, G., Roe, N., Yonce, H., Vallad, G., Adkins, S. 2011. Expansion of groundnut ringspot virus host and geographic ranges in solanaceous vegetables in peninsularFlorida. Plant Health Progress doi:10.1094/PHP-2011-0725-01-BR.
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Progress 09/01/10 to 08/31/11
Outputs
OUTPUTS: The overall goal of this project is to develop sound strategies for managing whitefly-transmitted viruses of vegetables, with emphases placed on Squash vein yellowing virus of watermelon and Tomato yellow leaf curl virus in tomato. Several studies were conducted as part of the project, and the annual progress report is given below. For the past 4 growing seasons, we received scouting reports for approximately 24,000 acres of tomato and vegetable production from cooperating growers and through our industry partner Glades Crop Care. The data were map and analyzed to identify environmental, geographical and/or management practices that may be linked to TYLCV epidemics as well as to identify alternate hosts that may exist in neighboring fallow fields, hedge rows, or unmanaged fields and forests. Results of this work were presented at the annual Florida Tomato Institute meeting in Naples, FL on September 8, 2010. Results of our spatial analyses of TYLCV epidemics indicate that a greater regional effort for managing whiteflies and TYLCV is needed. We hired ZedX Inc. to develop a web-based and smartphone technology platform (WSTP) for collection, analysis, and delivery of scouting information. Users of the WSTP will use their smartphone to collect and upload GPS-labeled scouting data (insect, disease, and production information) to a central server where it is processed and then delivered as real-time reports and management recommendations to growers and/or their scouts. The WSTP is being tested on a commercial scale by Glades Crop Care. Results of this work were presented at the annual Florida Tomato Institute meeting in Naples, FL on September 7, 2011. A trial to evaluate the efficacy of adding an insecticide (endosulfan) with or without crop oil to the herbicide (Gramoxone) treatment as a means to limit the migration of whiteflies to neighboring crops when chemically burning-down the tomato/watermelon crop after harvest was performed in several three to six acre blocks of commercial tomato and watermelon fields. Yellow sticky traps were placed at the north, south, east and west perimeters of each field 1 and 4 days prior to and after the burndown treatments, that is, a herbicide alone, mixed with endosulfan, and mixed with endosulfan and crop oil. Similar to the 2010 data, results were inconclusive in the tomato trial, primarily because the size of the field where the trial was conducted dictated that trap lines between treated plots overlap, thus making it difficult to separate treatment effects. The watermelon burndown study, showed the lowest migration out of the plot treated with the combination of Gramoxone/endosulfan/crop oil, and the highest coming from the plot treated with Gramoxone alone. We have conducted trials to determine the effect of SqVYV resistant pollenizers on spread of watermelon vine decline (WVD) on susceptible seedless watermelon. In trials conducted in spring and fall 2010 and spring 2011, the percentage of fruit with WVD symptoms was significantly less in plots with SqVYV resistant pollenizers compared to the susceptible pollenizer plots. This trial is being repeated one more time in fall 2011. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Analysis of the mapped whitefly and virus data continue to show that the severity of TYLCV follows the increase in mean whitefly density, as well as the average age of the fields in production. Most importantly, the data showed a strong correlation between neighboring fields, including 2nd and 3rd order neighbors (i.e., your neighbor's neighbor and their neighbors) for both disease and insect pressure. Translating results from relative to actual distance, the data showed that affected fields can impact other fields within a 1.5 mile radius. Analyses also showed the existence of hot spots for both whiteflies and virus, but they were not necessarily associated with each other or with a single grower or farm. A prominent hot spot was associated with the central growing area, which is typical given the concentration of production. Smaller hot spots were located around the edges or perimeters of farms and would be good areas to concentrate future surveys of the plant population. In addition, it was discovered that pigweed could serve as alternate host for Cucurbit yellow stunting disorder virus, a whitefly transmitted virus recently introduced in Florida cucurbit production. The plan for and early development of the WSTP was introduced at the 2010 Florida Tomato Institute meeting and the near finished product was introduced at the 2011 Tomato Institute meeting. The WSTP was developed to be broad and encompass not only TYLCV and whiteflies, but the multitude of insect pests and diseases that affect tomato and the wide variety of crops grown in Florida. The system is also designed to track various management practices that impact insect movement. Once the data has been uploaded and processed, the data can be mapped in variety of formats to allow participating growers to visualize the pest pressure on a regional scale. The WSTP also has the capacity to allow scouts to develop field-specific, pest management recommendations that can be delivered directly to growers on their phone or by email. Lastly, the WSTP will have various security features that will allow only certain data fields to be shared among the community of growers. Thus, the tool can serve the growers needs while also serving the community needs enabling growers to manage pests based on a regional, as well as local (e.g., farm), assessment of pest pressure.
Publications
- Adkins, S., Webster, C.G., Kousik, C.S. Webb, S.E., Roberts, P.D., Stansly, P.A., Turechek, W.W. 2011. Ecology and Management of Whitefly-Transmitted Viruses of Vegetable Crops in Florida. Virus Research 159:110-114.
- Adkins, S., Webster, C.G., McCollum, T.G., Albano, J.P., Turechek, W.W., Roberts, P.D., Webb, S.E., Baker, C.A., and Kousik, C.S. 2010. Physiological Effects Induced by Squash Vein Yellowing Virus, Causal Agent of Viral Watermelon Vine Decline in Florida in: Proceedings of Cucurbitaceae 2010, Nov. 14-18, 2010, Charleston, SC, pp 194-195.
- Kousik, C.S., Adkins, S, Webster, C.G., Turechek, W.W., Stansly, P., and Roberts, P. 2010. Effect of Reflective Mulch and Insecticidal Treatments on Development of Watermelon Vine Decline Caused by Squash Vein Yellowing Virus. Proceedings of Cucurbitaceae 2010, Nov. 14-18, 2010, Charleston, SC, pp 237-239.
- Turechek, W.W. 2010. Environmental and Geographical Variables Associated with TYLCV Epidemics in Southwest Florida in: Proceedings of the Tomato Committee Institute, Sept. 8, 2010, Naples, FL, pp15-16.
- Turechek, W.W. 2011. Tracking Disease and Insect Pests using Smartphone Technology: a New Approach for Regional Pest Management. Florida Tomato Institute, Sept. 7, 2011, Naples, FL, pp15-16.
- Turechek, W.W. Kousik, C.S., et al. 2010. Epidemiological Analysis of Multi-Virus Infections of Watermelon in Experimental Fields in Southwest Florida. International Symposium of Virus Epidemiology, June 20-24, Ithaca, NY.
- Turechek, W.W., Webster, C.G., Adkins, S., Stansly, P.A., Roberts, P.D., and Kousik, C.S. 2010. Epidemiology and Association of Four Insect Vectored Viruses in Florida Watermelon in: Proceedings of Cucurbitaceae 2010, Nov. 14-18, 2010, Charleston, SC, pp 208-209.
- Webster, C.G., Kousik, C.S., Roberts, P.D., Rosskopf, E.N., Turechek, W.W., and Adkins, S.A. 2011. Cucurbit yellow stunting disorder virus Detected in Pigweed in Florida. Plant Disease 95:360.
- Webster, C.G., Turechek, W.W., Kousik, C.S., Roberts, P.D., Webb, S.E., and Adkins, S. 2010. Response of Various Vining Cucurbits to Squash Vein Yellowing Virus Infection in: Proceedings of Cucurbitaceae 2010, Nov. 14-18, 2010, Charleston, SC, pp. 214-215.
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Progress 09/01/09 to 08/31/10
Outputs
OUTPUTS: Several studies were conducted as part of this SCRI grant with the overall goal of developing sound management strategies for managing whitefly-transmitted viruses of vegetables. A multi-year field study designed to characterize the spatial and temporal patterns of disease, quantify viral associations, and determine how environmental factors affect the development of SqVYV and CuLCrV was completed. The study was done over several growing seasons in a 1 ha field of cv. Fiesta watermelon at the University of Florida's Southwest Research and Education Center (SWFREC) in Immokalee, FL. Whitefly counts were taken on yellow sticky cards and on leaves, and virus incidence was assessed weekly from planting until harvest. In addition, environmental data was collected hourly through the course of the season using the Florida Automated Weather Network. Results of this work were presented at paper sessions at the Watermelon Research and Development Group meeting, Orlando, FL and and at the International Symposium of Virus Epidemiology, Ithaca, NY. Separate field studies were conducted to develop field-based strategies for managing WVD. In the first study, the effect of silver plastic mulch and insecticide treatments on managing WVD was evaluated in field plots of watermelon located at SWFREC. In a second study, two trials were conducted to determine the effect of SqVYV-resistant pollenizers in slowing down WVD in seedless melon production. Large scale field trials were conducted in commercial tomato and watermelon fields to determine the utility of adding an insecticide (crop oil) to the herbicide burndown treatment as a method to limiting the migration of whiteflies to neighboring crops. Several three to six acre blocks of watermelon or tomato were selected in commercial production fields to run the trial, and the blocks were spaced at distances from each other to prevent interplot interference. Yellow sticky traps were placed at the north, south, east and west perimeters of each field 1 and 4 days prior to and after the burndown treatments, that is, an herbicide with and without crop oil. A smaller version of this trial was also performed in four 0.6 acre watermelon fields in the summer of 2009 at the USDA, ARS research farm in Charleston, SC. A study to develop basic insect vector acquisition and transmission parameters for SqVYV, alone or in commonly observed mixed infections with CuLCrV, Papaya ringspot virus (PRSV-W) and/or Cucurbit yellow stunting disorder virus (CYSDV) was conducted. We studied the effect of mixed infections of PRSV-W and SqVYV on whitefly transmission of SqVYV to watermelon and squash plants. In addition, within plant distribution of adult and immature whiteflies on watermelon is being characterized to enable the development of more accurate sampling methods. In collaboration with growers we collected and analyzed insect and disease scouting reports from 80,000 acres of production and used regional weather data to determine spatial and temporal features associated with TYLCV epidemics and whitefly densities from the three county region that is the center of southwest Florida's vegetable production. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: We hired the company ZedX Inc. to help develop the decision support system. We re-arranged the budget and took funds originally designated for a post-doctoral associate and used then to hire a technician and the services of ZedX.
Impacts
From the multi-year field study, 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. In particular, the absence of disease in 2010 is believed to have been related to the hard freezes experienced across the region just prior to planting. In seasons where disease was prevalent, the data suggest that SqVYV and CuLCrV are being introduced by separate whiteflies, even though the whiteflies could emigrate from the same field. The data gathered from this study will be used to develop predictors of epidemic development that ultimately result in better control. No future plantings are planned. Results from the management-based studies showed that reducing whitefly populations using insecticide treatments significantly reduced WVD. Moreover, the percentage of watermelon fruit with WVD symptoms was significantly less in plots with SqVYV-resistant pollenizers compared to the susceptible pollenizer check plots. From the large-scale burndown trials, results were mixed but basically showed a modest reduction in whitefly migration in some plots but no effect in others. The trial will be repeated in subsequent crops. Results from the insect transmission/acquisition studies showed that SqVYV is not efficiently transmitted by whiteflies and is not retained for more than a day. SqVYV may require fairly high whitefly populations to spread rapidly. Results to date continue to be consistent with a semi-persistent mode of transmission for SqVYV. Results also showed that transmission of SqVYV from a plant that is also infected with PRSV-W is not affected when infection by SqVYV occurs before PRSV infection. However, when infection by PRSV-W occurs before SqVYV or simultaneously, transmission of SqVYV is reduced. We earlier found that if both viruses were introduced at the same time, transmission of PRSV-W from the infected plants by aphids was greatly reduced. Studies still remain to be conducted to look at the effect of mixed viral infections between CuLCrV and/or CYSDV and SqVYV. Tissue blot hybridization assays have been developed as improved diagnostics for all four cucurbit viruses to permit the large-scale testing required for epidemiological studies. These assays have been used to determine the within-plant distribution of these four viruses in watermelon plants with single or mixed infections. Data from the regional survey show that the severity of TYLCV closely followed 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.
Publications
- Adkins, S., Turechek, W.W., Kousik, C.S., Webb, S.E., Roberts, P.D., Stansly, P.A., and Baker, C.A. 2009. Watermelon vine decline and other whitefly-transmitted virus diseases of cucurbits in Florida. Proceedings of Southeastern Regional Vegetable Conference, Jan 9-11, 2009, Savannah, GA. Pg. 20.
- Adkins, S., Webster, C.G., Baker, C.A., Weaver, R., Rosskopf, E.N., and Turechek, W.W. 2009. Detection of three whitefly-transmitted viruses infecting the cucurbit weed, Cucumis melo var. Dudaim, in Florida. Plant Health Progress doi:10.1094/PHP-2009-1118-01-BR.
- Kousik, C.S., Adkins, S.T., Webster, C.G., Turechek, W.W., and Roberts, P.D. 2010. Effect of reflective plastic mulch and insecticide sprays on viral watermelon vine decline in Florida, 2009. Plant Disease Management Reports 4:V149.
- Turechek, W.W., Adkins, S.A., Kousik, C.S., Webster, C.G., Stansly, P.A., and Roberts, P.D. 2009. Epidemiological analysis of multi-virus infections of watermelon in experimental fields in Southwest Florida. Phytopathology 99:S131.
- Turechek, W.W., Kousik, C.S., and Adkins, S. 2010. Distribution of four viruses in single and mixed infections within infected watermelon plants in Florida. Phytopathology 100:1194-1203.
- Webb, S, Roberts, P.D., Stansly, P.A., Adkins, S., Turechek, W.W., and Kousik, C.S. 2009. Managing whitefly vectors of three cucurbit viruses new to Florida. Phytopathology 99:S171.
- Webster, C.G., Kousik, C.S., Turechek, W.W., Webb, S.E., and Adkins, S. 2009. Symptoms and distribution of Squash vein yellowing virus in vining cucurbits. Phytopathology 99:S139.
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Progress 09/01/08 to 08/31/09
Outputs
OUTPUTS: A 2.5 acre watermelon field was planted at the University of Florida's Southwest Research and Education Center in Immokalee, FL to allow us to monitor and characterize the spatial and temporal characteristics of viral epidemics and whitefly populations in a setting where whitefly populations are left unmanaged. The field was scouted and whitefly and aphid counts were gathered weekly beginning 1 week after planting until harvest. In addition, environmental data was collected using the Florida Automated Weather Network. We continue to receive weekly scouting reports of whitely densities and virus incidence in commercially produced tomato, watermelon, and potato crops from our collaborators in southwest Florida. The data are entered into the GIS program ArcView which permits us to map and view the data at any given time and location of our choosing. We are in the process of analyzing the data to determine factors that contribute to viral epidemics on a regional scale, but the analysis generally requires several years of data to sufficiently identify trends which have yet to collect. A trial to determine the value of adding an insecticide (crop oil) to the post-harvest, herbicide burn-down treatment was evaluated for its ability to limit the migration of whiteflies to neighboring crops in commercial tomato and watermelon fields. Several three to six acre blocks of watermelon or tomato were selected in commercial production fields to run the trial, and the blocks were spaced at distances from each other to prevent interplot interference. Yellow sticky traps were placed at the north, south, east and west perimeters of each field and evaluated 1 and 4 days prior to and after the burndown treatments, that is, an herbicide with and without crop oil (the insecticide). Lastly, a meeting was convened with our grower collaboartors to discuss the progress of the first year of the study and to make plans for the following years. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: We redirected funds to hire ZedX Inc. to develop the web-based interface for the decision support system rather than hiring a post-doctoral associate.
Impacts
Data from the first year of the study are currently being analyzed. There are no significant outcomes or impacts to report.
Publications
- No publications reported this period
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