Challenges in Producing Nematode- and Pathogen-Free Fruit and Nut Nursery Crops in the United States
Abstract:The 2006 gross value of fruit and nut nursery crops in the United States was $276 million. This category includes citrus and subtropical fruit trees, deciduous fruit and nut trees, grapevines, and other small fruit plants, such as raspberry and strawberry. California produces the majority of the fruit and nut nursery stock sold in the United States, with Oregon and Washington also producing a significant proportion. A critical component in the production and sale of these nursery crops is the generation of planting stock that is free of viruses, soil-borne pathogens, and plant-parasitic nematodes. To achieve plant-parasitic nematode and soil-borne pathogen control, fruit and nut nursery crop producers have relied upon preplant soil fumigation with combinations of methyl bromide and chloropicrin. This method allows the producer to reduce significantly or eliminate plant-parasitic nematodes and soil-borne pathogens and helps mitigate the risk of developing infected plant material. Methyl bromide is classified as a restricted-use pesticide and was registered for use in the United States in 1961 as an effective herbicide, nematicide, insecticide, and fungicide. In the late 1980s and early 1990s, methyl bromide was one of the five most used pesticides in the United States, with 75% of the use being for preplant soil fumigation. Despite the widespread use of this pesticide, methyl bromide was targeted for phase-out under the Montreal Protocol due to its ability to deplete stratospheric ozone. However, the Montreal Protocol allows for critical use exemptions (CUE) to the ban if 1) there are no technically and economically feasible alternatives that are acceptable from a regulatory and bystander exposure perspective, and 2) the use is considered crucial to avoid a significant market disruption of selected commodities. Since this time, US fruit and nut nurseries have been able to obtain CUEs to continue to use methyl bromide. Nurseries in the United States have also qualified for quarantine/preshipment exemptions based upon import regulations requiring that plants be grown in soil fumigated with methyl bromide.
Document Type: Short Communication
Publication date: October 1, 2010
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