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United States Department of Agriculture

Agricultural Research Service

Research Project: AN ARS AREAWIDE PEST MANAGEMENT (AWPM)PROGRAM FOR METHYL BROMIDE ALTERNATIVES Title: Perennial Crop Nurseries Treated with Methyl Bromide and Alternative Fumigants: Effects on Weed Seed Viability, Weed Densities, and Time Required for Hand Weeding

Authors
item Shrestha, Anil - UNIV OF CALIF, PARLIER
item Browne, Greg
item Lampinen, Bruce - UNIV OF CALIF, DAVIS
item Schneider, Sally
item Simon, Leo - UNIV OF CALIF, BERKELEY
item Trout, Thomas

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 1, 2008
Publication Date: June 1, 2008
Citation: Shrestha, A., Browne, G.T., Lampinen, B.D., Schneider, S.M., Simon, L., Trout, T.J. 2008. Perennial crop nurseries treated with methyl bromide and alternative fumigants: effects on weed seed viability, weed densities, and time required for hand weeding. Weed Technology. 22:267-274

Interpretive Summary: Weed control provided by alternative fumigants to methyl bromide (MeBr) needs to be tested in perennial crop nurseries in California because MeBr is being phased out in accordance with the Montreal Protocol, few herbicides are registered for perennial nursery use, and costs of other control measures are prohibitive. Field studies were conducted in four commercial perennial crop nurseries in California. Treatments included the following shank-applied treatments: a non-fumigated control; MeBr with (i.e., covered by) high density polyethylene film (HDPE); iodomethane (50%) plus chloropicrin (50%) with HDPE; 1,3-dichloropropene (1,3-D) with HDPE; 1,3-D (61%) plus chloropicrin (35%) with HDPE or virtually impermeable film (VIF), and, at two of the nurseries, a sub-surface drip-applied treatment: 1,3-D (62%) plus chloropicrin (35%) with HDPE. All the fumigants reduced the seed viability of weeds such as common purslane, johnsongrass, and tall morningglory but were not as effective on little mallow or field bindweed. Although total weed densities and the level of control provided by each fumigant differed between locations, weed seedling emergence was generally reduced by all the fumigation treatments, compared to the non-fumigated control. At three of the nurseries, the alternative fumigation treatments resulted in hand weeding time similar that for the MeBr treatment. Reductions in weed seed viability, weed emergence, and weed densities suggest that use of the alternative fumigation treatments, in general, will result in weed control similar to that provided by MeBr in perennial nurseries.

Technical Abstract: Weed control provided by alternative fumigants to methyl bromide (MeBr) needs to be tested in perennial crop nurseries in California because MeBr is being phased out in accordance with the Montreal Protocol, few herbicides are registered for perennial nursery use, and costs of other control measures are prohibitive. Field studies were conducted in four commercial perennial crop nurseries in California. Treatments included the following shank-applied treatments: a non-fumigated control; MeBr with (i.e., covered by) high density polyethylene film (HDPE); iodomethane (50%) plus chloropicrin (50%) with HDPE; 1,3-dichloropropene (1,3-D) with HDPE; 1,3-D (61%) plus chloropicrin (35%) with HDPE or virtually impermeable film (VIF), and, at two of the nurseries, a sub-surface drip-applied treatment: 1,3-D (62%) plus chloropicrin (35%) with HDPE. All the fumigants reduced the seed viability of weeds such as Portulaca oleracea L., Sorghum halepense L., and Ipomoea sp. but were not as effective on Malva parviflora L. and Convolvulus arvensis L. Although total weed densities and the level of control provided by each fumigant differed between locations, weed seedling emergence was generally reduced by all the fumigation treatments, compared to the non-fumigated control. At three of the nurseries, the alternative fumigation treatments resulted in hand weeding time similar that for the MeBr treatment. Reductions in weed seed viability, weed emergence, and weed densities suggest that use of the alternative fumigation treatments, in general, will result in weed control similar to that provided by MeBr in perennial nurseries.

Last Modified: 10/24/2014