Submitted to: Proceedings California Plant and Soil Conference Farming in Crisis
Publication Type: Proceedings
Publication Acceptance Date: February 1, 2004
Publication Date: February 2, 2004
Citation: Schneider, S.M., Trout, T.J., Gerik, J.S., Ajwa, H.A. 2004. Methyl bromide alternatives for perennial crops and field nurseries.. Proceedings California Plant and Soil Conference Farming in Crisis. Feb. 2004. p. 104-112. Interpretive Summary: Methyl bromide (MB) is commonly used to fumigate the soil in order to insure healthy crops when planting new orchards or vineyards back into soil where trees or vines had been grown and when growing the small trees and vines that will be used to plant new commercial orchards and vineyards. The nursery trees must be free from all diseases and pests, otherwise the problems can spread when the trees and vines are moved to the production vineyards and orchards. Beginning in January 2005, MB will no longer be available except for approved critical uses and quarantine uses, so growers will need other ways to protect their crops. Iodomethane (IM) or 1,3-dichloropropene (1,3-D) combined with chloropicrin (Pic) appear to be good alternatives for nematode control when both rootknot and citrus nematodes are present, but IM is not yet approved for use and use of 1,3-D is limited by township caps in California. Resistant rootstocks are effective tools if resistance is available for all the pests and pathogens in a given vineyard, but this range of resistance is often not available . IM, 1,3-D/Pic, pic, and metam sodium provided good nematode control during the first year of the two-year growing cycle for rose nurseries, but data on the 2nd year was not yet available. In a commercial tree and vine nursery, shank-injected fumigants were more effective when the soil was covered by a plastic tarp immediately after the chemical was applied than when tarps were not used. Several promising alternatives were identified in these trials, but additional research is needed to confirm the performance over a range of growing conditions.
Technical Abstract: Methyl bromide is a widely used soil fumigant for nematode and pathogen control both in field nurseries and to manage perennial replant disorder. The Montreal Protocol restricted availability of methyl bromide beginning in January, 2001 and will reach a total phaseout, other than Critical Use Exemptions and quarantine use, in 2005. U.S. growers of perennial nursery crops and those replanting orchards and vineyards are in dire need of alternatives to methyl bromide. Iodomethane (IM), 1,3-dichloropropene (1,3-D)/metam sodium combinations, and 1,3-D/chloropicrin (Pic) appear to be good alternatives to methyl bromide for vineyard replant when both rootknot and citrus nematode are present. Iodomethane is not yet registered and use of 1,3-dichloropropene is restricted in California by township caps. The Harmony rootstock continues to support only minimal populations of the rootknot nematode after 5 growing seasons, but supports higher populations of the citrus nematode than either Thompson Seedless or Teleki 5C. Efficacy of long-term fallow treatments for vineyard replant depends on nematode genera present but are not as effective as methyl bromide. Im/Pic, 1,3-D/Pic, chloropicrin, and metam sodium achieved nematode control similar to methyl bromide at the beginning of the 2nd growing season in a rose field nursery, BUT performance of these materials at the end of the cropping cycle is not yet known. Tarped, shank-injected applications gave better control than untarped, shank-injected applications in a commercial vine nursery, but tarping represents an additional cost. New materials and new rootstocks evaluated here are potential tools in management of nematodes under nursery conditions without methyl bromide, but performance throughout the cropping cycle is not yet known.