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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #200600
Title: Glyphosate hinders nutsedge tuber production

Author
item Webster, Theodore
item GREY, T - UNIV. OF GA, TIFTON,GA
item CULPEPPER, A - UNIV. OF GA, TIFTON,GA

Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: 9/17/2006
Publication Date: 11/6/2006
Citation: Webster, T.M., Grey, T.L., Culpepper, A.S. 2006. Glyphosate hinders nutsedge tuber production. In: Proceedings of the International Research Conference on Methyl Bromide Alternatives and Emissions Reductions, November 6-9, 2006, Orlando, FL. p. 128.1-128.2.

Interpretive Summary: Price and availability of methyl bromide (MB) will soon limit its use on Georgia farms. MB alternatives for many diseases and nematodes do exist. Recent research has focused on nutsedge response to MB alternatives in conjunction with various types of mulch. A study evaluated five fumigant options with four types of mulch. Nutsedge control in all treatments was similar to that of MB applied under low density polyethylene (LDPE) mulch, except from 1,3-dichloropropene under LDPE which had lower control. Nutsedge emergence occurred on the bed shoulder, indicating a fumigant placement issue. Early-season pepper growth was slower with metalized silver mulch due to cooler soil temperatures. All fumigant alternative systems, except for methyl iodide under virtually impermeable film, produced pepper yields at least as good as the standard MB under LDPE mulch. Yields from methyl iodide under VIF were less than those of MB because of early-season fumigant injury. Although results have been promising in 2005 and 2006 in adopting MB alternatives in small plots, numerous limitations must be addressed prior to wide-scale grower adoption, including: 1) results from small plot research must be verified in large acreage on-farm trials, 2) data is needed to address plant back intervals after fumigating with these alternatives, 3. determining the efficacy of these fumigant alternatives on weeds other than nutsedge, 4) evaluating the economic viability of alternative mulches, 5) development and registration of new herbicide tools for vegetable growers.

Technical Abstract: Many alternative fumigants have struggled to achieve nutsedge control equivalent to methyl bromide. Effective management strategies will need to minimize nutsedge tuber production. Glyphosate has been shown to reduce tuber production, but it is not clear what the minimum dose is to reduce tuber production. Greenhouse studies evaluated glyphosate dose on nutsedge tuber production. Glyphosate was applied at 0, 0.41, 0.59, 0.74, 0.95, and 1.23 kg ae/ha. Tuber production in each plot was evaluated at 5 weeks after application. Tubers were classified based on their relative position to the initial planted tuber. Tubers that were directly attached to the initial tuber were considered 1st-order tubers, 2nd-order tubers were attached to 1st-order tubers, and 3rd-order tubers attached to 2nd-order tubers, etc. The 6th- and 3rd-order tubers were terminal for purple and yellow nutsedge, respectively. The lowest rate of glyphosate stimulated purple nutsedge tuber biomass accumulation, while reducing yellow nutsedge tubers >37%. Glyphosate at 0.59 kg/ha reduced 2nd-order tuber biomass in purple nutsedge 35% and yellow nutsedge 76%. All rates of glyphosate reduced tuber biomass in 3rd- and 4th-order purple nutsedge and 3rd-order yellow nutsedge >67%. Glyphosate reduced 5th- and 6th-order purple nutsedge tubers. The lowest rate of glyphosate reduced purple and yellow nutsedge tuber biomass 20% and 50%, respectively. Glyphosate at 0.95 kg/ha reduced tuber biomass >85% for both nutsedge species.