Subsurface drip application of alternative fumigants to methyl bromide for controlling nematodes in replanted grapevines.

BACKGROUND: Many California grape growers use preplant fumigation to ensure uniform and healthy grapevine establishment in replant situations. A field study was conducted to evaluate the performance of subsurface drip-applied chemical alternatives to methyl bromide on plant-parasitic nematodes, plant vigor and fruit yield during the 6 year period following replanting. RESULTS: Subsurface drip fumigation with 1,3-dichloropropene plus chloropicrin and with iodomethane plus chloropicrin had generally similar nematicide activity as methyl bromide in three grape types, while sodium azide was less effective. The combination of 1,3-dichloropropene plus chloropicrin enhanced vine vigor similarly to methyl bromide. However, all plots treated with alternative fumigants produced less fruit yield than methyl bromide over the 4 years of evaluation. CONCLUSION: Subsurface drip fumigation with alternative chemicals to methyl bromide generally provided adequate management of plant-parasitic nematodes during the vine establishment period. However, further research is required to increase the performance of alternative chemicals against other components of the replant problem, as grape yield in vines grown in the alternative treatments was lower than in methyl bromide.

Effects of reduced-rate methyl bromide applications under conventional and virtually impermeable plastic film in perennial crop field nurseries.

BACKGROUND: Producers of perennial crop nursery stock in California use preplant soil fumigation to meet state phytosanitary requirements. Although methyl bromide (MB) has been phased out in many agricultural industries, it is still the preferred treatment in the perennial nursery industry and is used under Critical Use Exemptions and Quarantine/Preshipment provisions of the Montreal Protocol. The present research was conducted to evaluate reduced-rate MB applications sealed with conventional and low-permeability plastic films compared with the primary alternative material. RESULTS: Reduced rates (100-260 kg ha(-1)) of MB applied in combination with chloropicrin (Pic) and sealed with a low-permeability plastic film provided weed and nematode control similar to the industry standard rate of 392 kg ha(-1) MB:Pic (98:2) sealed with high-density polyethylene (HDPE) film. However, the primary alternative chemical, 1,3-dichloropropene (1,3-D), tended to provide slightly lower pest control even on sites with relatively low plant parasitic nematode, soil-borne pathogen and weed pest pressure. CONCLUSION: If California regulations change to allow the use of low-permeability films in broadcast fumigant applications, the results of this research suggest that reduced rates of MB in perennial crop nurseries could serve as a bridge strategy until more technically, economically and environmentally acceptable alternatives are developed.

United States Department of Agriculture-Agricultural Research Service research on alternatives to methyl bromide: pre-plant and post-harvest.

Methyl bromide is a widely used fumigant for both pre-plant and post-harvest pest and pathogen control. The Montreal Protocol and the US Clean Air Act mandate a phase-out of the import and manufacture of methyl bromide, beginning in 2001 and culminating with a complete ban, except for quarantine and certain pre-shipment uses and exempted critical uses, in January 2005. In 1995, ARS built on its existing programs in soil-borne plant pathology and post-harvest entomology and plant pathology to initiate a national research program to develop alternatives to methyl bromide. The focus has been on strawberry, pepper, tomato, perennial and nursery cropping systems for pre-plant methyl bromide use and fresh and durable commodities for post-harvest use. Recently the program has been expanded to include research on alternatives for the ornamental and cut flower cropping systems. An overview of the national research program is presented. Results from four specific research trials are presented, ranging from organic to conventional systems. Good progress on short-term alternatives is being made. These will be used as the foundation of integrated management systems which begin with pre-plant management decisions and continue through post-harvest processing.