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DEVELOPMENT OF ALTERNATIVE STRATEGIES FOR MANAGEMENT OF SOILBORNE PATHOGENS CURRENTLY CONTROLLED WITH METHYL BROMIDE 1
Key Words 1,3-dichloropropene, metam sodium, chloropicrin, integrated control, biological control
Abstract The current standard treatment for management of soilborne pests in some high-value crop production systems is preplant fumigation with mixtures of methyl bromide and chloropicrin. With the impending phase-out of methyl bromide, the agricultural industries that rely on soil fumigation face the need for development of alternative pest management strategies. To maintain farm productivity, immediate term research has focused on evaluation of alternative fumigants, modification of current crop production practices to accommodate their use, and improvement of application technologies to reduce the environmental effects of fumigant applications. Longerterm research goals have focused on developing a more integrated approach for pest management that incorporates the use of cultural practices to reduce pathogen pressure, host resistance to disease, and biological approaches for stimulating plant growth and control of root diseases.
INTRODUCTION
For the past four decades, methyl bromide (MB) has been the fumigant of choice for many preplant soil applications. The reasons primarily focus on the broad spectrum of activity of the fumigant, its high vapor pressure facilitating distribution through the soil profile, cost-effectiveness, and comparatively short plant-back intervals. For field crops it is generally applied by shank as a broadcast treatment with shank traces compacted or the top of soil that is covered with a polyethylene plastic tarp. More recently fumigation has been done by shank application into preformed beds and covering the beds with plastic tarps. Due to the synergistic activity that broadens the spectrum of pest control, applications are often combined with chloropicrin. Historically, MB was used primarily to control lethal soilborne pathogens such as Verticillium dahliae (86), but it also can provide excellent control of nematodes and a broad spectrum of weeds. This review focuses on the control of soilborne pathogens, but for the grower, this represents only part of the equation. The cost-effectiveness of preplant soil fumigation is measured by how it affects the total farming operation, ranging from post-fumigation plant-back intervals that may shorten the previous production cycle to allow enough time to fumigate and prepare the field for the next planting, management of weeds to reduce labor costs, to how...