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Alternatives to Methyl Bromide for the Control of Bacterial Wilt and Yellow Nutsedge in Tomatoes and Peppers Grown in Virginia


The primary goal of this research is to supplement vegetable growers' available management strategies of disease suppression with new and viable practices, during the transition to a methyl bromide-free program, specifically as it pertains to the tomato and pepper production regions of the Eastern Shore of Virginia and the Mid-Atlantic. This will be achieved by defining effective and economically feasible alternative management strategies of the two major limiting factors of production: bacterial wilt and invasion by noxious weeds. <P>Chemical (alternative fumigants), cultural (grafting and mulch use), and some novel approaches (irrigation water sanitation) will here be proposed. To complete such varied work, a multidisciplinary team has been assembled across a broad spectrum of expertise.<P> Research, extension and education components will all play vital roles in the following research, with the goal of findings that would have immediate and far-reaching impact for the vegetable industry of Virginia, the Mid-Atlantic United States, and possibly further. <P>Use of effective, economic and low environmental-impact management practices, in lieu of methyl bromide, will benefit the industry and the environment for generations to come.

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Non-Technical Summary: Virginia ranks third in the U.S. in fresh-market tomato production, with the majority of acres grown on plasticulture, utilizing methyl bromide (MeBr). Bell peppers are grown using similar production practices. Both of these crops are highly susceptible to soilborne pests and overgrowth by noxious weeds. The use of MeBr has been the primary tool to suppress these pest problems, and tomatoes and peppers are listed as MeBr Critical Use Nominations for 2009. Our project focuses on integrated commercial and field-scale research that targets short- to medium-term solutions to the loss of MeBr in tomato and pepper production, and includes associated extension activity to foster the adoption of these solutions. To complete such varied work, a multidisciplinary team has been assembled across a broad spectrum of expertise. Commercially-available alternatives to MeBr are neither technologically nor economically feasible for tomato or pepper production. In this project, we propose to investigate some novel tactics that have had success in other areas, but have not been investigated in VA. Specific goals include: 1) evaluating released and unreleased lines of tomatoes and peppers for natural resistance to various diseases; 2) grafting current tomato varieties onto resistant rootstocks; 3) evaluating the efficacy of alternative chemical treatments such as peroxyacetic acid and thyme oils as well as others; 4) assess effects of experimental treatments on soil fauna in agroecosystems; 5) determine potential for bacterial contamination within irrigation water sources and subsequent spread to fields, and investigate methods of in-line sanitization; 6) analyze specific weed susceptibility to alternatives investigated; and 7) initiate a technology transfer program to disseminate research results to producers and train a doctorate level researcher. <P> Approach: Bacterial wilt resistant tomato lines and cultivars from the University of Florida tomato breeding program, BHN Seed, and D. Palmer Seed Co. (Yuma, AZ) will be evaluated in these trials. Grafted tomato seedlings will also be included in this trial. A single cultivar will be used as the scion along with at least two bacterial wilt-resistant rootstock cultivars. In addition, each cultivar will be evaluated for enhanced bacterial wilt resistance in response to treatment with labeled rates of ASM, as compared to non-treated controls. Seedlings will be grown in the greenhouse for approximately five weeks prior to transplanting. Grafting will occur in the greenhouse at roughly five week after planting, and grafted seedlings will be transplanted to field plots at the same time as non-grafted seedlings, about six weeks after planting. Transplants will be set in a naturally infested commercial field(s) in virtually impermeable film (VIF) polyethylene mulch. The trial will be set up in a split-plot design with the ASM treatment being the main plot and the resistant lines and cultivars the sub plots. Treatments will be replicated four times, with individual plots measuring 15m long on 1.8m row centers. Transplants will be spaced 46 cm apart within rows. ASM-treated main plots will be sprayed with ASM weekly in accordance with the label (according to growth stage; up to 8 applications in accordance with Virginia's 24c Actigard 50WG label on tomatoes). Bacterial wilt incidence will be assessed weekly. Mature green tomato fruit will be harvested as necessary. For each harvest, by plot, marketable fruit will be sized utilizing commercial standards and weighed for yields. Data for each harvest (and cumulative totals) will be analyzed by ANOVA for main and sub plot effects.

Rideout, Steven
West Virginia University
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