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Title: Efficacy of glyphosate and halosulfuron for control of purple and yellow nutsedge in elevated CO2 environments

item MARBLE, S - University Of Florida
item Prior, Stephen - Steve
item Runion, George
item Torbert, Henry - Allen

Submitted to: Southern Region of the American Society for Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: 1/30/2015
Publication Date: 1/30/2015
Citation: Marble, S.C., Prior, S.A., Runion, G.B., Torbert III, H.A. 2015. Efficacy of glyphosate and halosulfuron for control of purple and yellow nutsedge in elevated CO2 environments [Abstract]. Proceedings of the Southern Region of the American Society for Horticultural Science. 50(9):S45.

Interpretive Summary:

Technical Abstract: Carbon dioxide (CO2) concentrations in the earth’s atmosphere have continually increased each year since the beginning of the Industrial revolution and are expected to continue rising in the future, which could have a dramatic impact on agricultural production. Previous research has shown that elevated CO2 levels increase the growth and yield of most plant species. Although many crops will likely benefit from increasing levels of CO2 in terms of growth and yield, this benefit could be negated due to increased growth of weed species and the occurrence of herbicide resistant weed biotypes. Currently, scientists are concerned that global climate change could reduce the effectiveness of herbicides at current label rates. In summer of 2012, an experiment was conducted to determine if labeled rates of glyphosate (RoundUp Pro®) and halosulfuron (SedgeHammer®) would provide effective control of purple nutsedge (Cyperus rotundus L.) and yellow nutsedge (Cyperus esculentus L.) in an elevated CO2 environment. Yellow and purple nutsedge tubers were grown in 3.0 L containers in either ambient or elevated (ambient + 200 µmol mol-1) CO2 in open-top chambers and treated with 0.5×, 1.0× or 1.5× the labeled rate of each herbicide and a tank mix of each herbicide at the specified rates. At the time of treatment, purple and yellow nutsedge were approximately 10 and 20 cm tall, respectively. Results showed a positive growth response for both nutsedge species when they were grown in elevated CO2 chambers as purple nutsedge increased shoot and root dry weights and tuber counts by 27%, 25%, and 25%, respectively, in comparison to plants grown at ambient levels. Yellow nutsedge had a greater response to elevated CO2, increasing shoot, root, and tuber dry weights by 40%, 51%, and 100%, respectively, and tuber counts increased by 128%. Few differences were observed among herbicide treatments or rates, and all provided over 90% control in both elevated and ambient CO2 environments. Based on the results of this study, it appears that although elevated CO2 levels will increase the growth of both weed species, predicted future CO2 levels will likely not impact the efficacy of halosulfuron or glyphosate for control yellow and purple nutsedge at growth stages described here. Both herbicides provided acceptable control of both nutsedge species when applied prior to the flowering stage at currently labeled rates. It is unclear if the efficacy of these active ingredients or rates would have been affected by delaying applications until either species reached maturity. It is important to note that although this study focused on a single treatment scenario, repeated herbicide applications or a combination of herbicide applications and cultural practices will likely be needed for long-term control of perennial nutsedges in a field setting.