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Reducing the Risks of Salmonellosis on Maryland-grown Fresh-Market Tomatoes Through a Coordinated Research and Extension Education Program


Study the seasonal changes and the effects of water source used for pesticide applications on the naturally-occurring epiphyte populations present on tomato fruit grown at two representative locations in Maryland. Develop an up-to date GAPs training program for Extension Educators, tomato producers and marketers in Maryland that specifically addresses relevant, science-based programs for reducing the risk of Salmonellosis in locally-produced tomatoes

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NON-TECHNICAL SUMMARY: The primary goal of this proposal is to reduce the risk of Salmonella for producers and consumers of fresh tomatoes grown in Maryland. To do this we expect to develop a team that will serve three different audiences; Extension Educators, Vegetable Producers, and the Food Safety and Scientific Community. To test the impact of this program we will monitor the implementation of the following Awareness of the need for GAPs in the wholesale tomato industry Increase in the number and acreage of GAPs Certified Producers in Maryland Development of additional scientific information and the collaboration with others Awareness will be monitored by pre and post tests administered to Extension Educators at the In-Service training, and producers at the proposed Tomato Workshop in Winter, 2008. The increase in the number and acreage of GAPs Certified Producers will be followed by direct contacts made with third-party auditors working in the DelMarVa Region. <P>

APPROACH: Replicated tomato plots will be planted at two locations on University of Maryland Research and Extension Centers in 2008. Plantings will be set at WyeREC silt loam soil in Queenstown, Maryland and LESREC sandy soil in Salisbury, Maryland. Small plots of tomato will be established. Tomato transplants will be grown at the research greenhouses in College Park and set in late-spring to be harvested during the critical risk period of August and September. To simulate current industry conditions, tomato will be grown using plastic mulch and trickle irrigation. This project will require 10 plots at each location five sprayed with surface water and five sprayed with groundwater. Each plot will consist of a single 10 foot 3 3m row which will be surrounded by a large unplanted buffer strip. A separation between plots of 50 feet 16 5m will be kept weed free to minimize cross-contamination between plots. One-half acre of land will be required at each location to conduct this study. The primary factor tested in this study will be source of water used to mix pesticides. Ground water from wells will be compared to surface water from farm ponds at each location. Growers typically use insecticide fungicide mixtures at 7 to 14 day schedule during the growing season. With the high pesticide usage required for tomato production in humid climates, this typically equates to 8 to 10 applications during the period of high temperature and humidity July 15-September 15. That is the window when Salmonella Newport outbreaks have occurred. Pesticides will be mixed and applied by agricultural technicians who are licensed pesticide applicators using small-plot backpack sprayers. Technicians will make applications of identical materials to all plots on the same date. Treatments will differ only in source of water used to mix pesticides. Between applications, multiple rinses will be used to avoid cross-contamination. To develop longitudinal data on the effects of location and sampling date on epiphytes living on the surface of tomato leaves and fruits, samples will be taken once a month from each plot. Sampling will be conducted on or about July 15, August 14 and September 15, 2008. With ten plots at each location five groundwater vs. five surface water and two locations, this protocol will yield 60 samples for DNA extraction during the growing season. At three dates during the season, tomato fruit and leaves will be collected from each of the replicated blocks at Wye and Salisbury. Leaves and apples will be aseptically and systematically removed from each tree and transported back to the laboratory in sealed bags at approximately 25 C. Ten leaves and three apples will be placed in 300 ml of deionized water in a sealed container and sonicated for five minutes to dislodge phyllopshere microbial species from fruit and leaf surfaces.

Walsh, Christopher
University of Maryland - College Park
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