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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #200623
Title: Methyl bromide alternatives being identified in Georgia

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

Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: 9/22/2006
Publication Date: 11/6/2006
Citation: Culpepper, A.S., Davis, A.L., Webster, T.M. 2006. Methyl bromide alternatives being identified in Georgia. In: Proceedings of the Annual International Conference on Methyl Bromide Alternatives and Emissions Reductions, November 6-9, 2006, Orlando, FL. p. 65.1-65.4.

Interpretive Summary: Many alternative fumigants do not control nutsedge equivalent to methyl bromide. Effective management strategies will likely need to include other tactics that target nutsedge populations between crops. The key to successful nutsedge management is hindering nutsedge tuber production, the primary means that these weeds reproduce. Greenhouse studies evaluated the effect of glyphosate rate on purple nutsedge and yellow nutsedge tuber production. Glyphosate was found to be an effective means of reducing tuber production in both purple and yellow nutsedge. Yellow nutsedge appeared to be more sensitive to glyphosate than purple nutsedge. Tuber populations develop rapidly, producing 60 tubers in 13 weeks. Each purple nutsedge shoot represents approximately 4 tubers. Glyphosate will be an important component of effective long-term management nutsedge programs, allowing for repeated applications due to its relatively low cost and poses no soil residual herbicide carryover issues to vegetable crops. In Georgia, glyphosate-resistant Palmer amaranth (Amaranthus palmeri) has been documented in cotton fields. This species will likely become a more important weed in vegetables. Judicious use of glyphosate is warranted.

Technical Abstract: It has become clear that the 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 was conducted in the spring of 2006 near Ty Ty, GA. Treatments were five fumigant options: MB (67%)+chloropicrin (Pic) (350 lb/A), methyl iodide (50%)+Pic (350 lb/A), dimethyl disulfide (79%)+Pic (75 gal/A), 1,3-dichloropropene (1,3-D) (12 gal/A)+Pic (150 lb/A)+metham (75 gal/A), and non-fumigated. Four different mulches were used for each fumigant: black low density polyethylene, metalized smooth silver side up, metalized smooth black side up, and virtually impermeable film (VIF). Fumigants were applied on 22 February 2006 and bell pepper transplanted 20 days later. Purple nutsedge was uniformly distributed in the test; numbers of nutsedge plants were counted bi-weekly. Jumbo pepper fruit were harvested five times. Nutsedge control in all treatments was similar to that of MB applied under LDPE mulch, except for 1,3-D under LDPE, which was higher. 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 VIF, produced pepper yields at least as good as the standard MB under LDPE mulch. Yields from MIDAS under VIF were less than those of MB because of early-season fumigant injury.