survey of giant ragweed distribution and spread in the north central region regnier, e., c....
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Survey of Giant Ragweed Distribution and Spread in the North Central Region
Regnier, E., C. Holloman, S. K. Harrison, M. Loux, R. Venkatesh, R. Ford, R. Taylor*, & F. Diekmann
Ohio State University, Columbus, OH
*Texas A&M University, Temple, TX
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BACKGROUND
North American native riparian species
Increasing problem in crop fields in the last 30 years
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(1852)
Date of first collection for herbaria
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Date of reported herbicide resistance
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Hypothesized steps in spread of GRW
• Spread from E to W• Adaptation from riparian to upland habitats• Spread from non-crop borders into crop fields• Evolution of prolonged emergence period• Facilitated by reduced tillage and POST
herbicide
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Survey of North Central States
• Certified crop advisors• Distributed online by ASA• July 2013• Exploratory data analysis
– Mapping– Correlation analysis
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In terms of management, how would you rate giant ragweed?
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rMD = correlation with management difficulty, p < 0.05
Management Difficulty
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Has herbicide-resistant GRW been suspected or confirmed (to ALS-inhibitors, to Glyphosate, to both)?
Yes, confirmed Yes, suspected
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Has herbicide-resistant GRW been suspected or confirmed?Management Difficulty
Yes, confirmed Yes, suspected
Corn, soybean, wheat:rMD = .19 to .28Cotton: ns
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What percentage of noncrop acreage has giant ragweed present?
rMD = .22
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What percentage of crop acreage has giant ragweed present?
rMD = .22
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How long ago was GRW first observed in areas outside of crop fields?
rMD = ns
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How long ago was GRW first observed in crop fields?
rMD = ns
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In which non-crop environment did giant ragweed first appear?
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In which non-crop environments have you observed giant ragweed?
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Number of checked non-crop environments
rMD = .18
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Presence of giant ragweed in waterways
rMD = .19
% of respondents answering yes
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Presence of giant ragweed in fencerows
% of respondents answering yes
rMD = .11
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Correlation of GRW presence in non-crop habitat and resistance
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When does giant ragweed first emerge as seedlings?
rMD = -.22
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Giant ragweed emergence period
(months)rMD = .19
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On what percentage of crop acreage is each of the following practices used?
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Correlation of herbicide practice with GRW management difficulty
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Correlation of perceived GRW resistance source with management difficulty
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SummaryHypothesized steps in spread of GRW
• Spread from E to W – from center outwards
• Movement from crop borders into crop fields– Railroads, fencerows, ditch-banks, waterways
• Adaptation to upland habitats – for over 20 yrs
• Evolution of prolonged emergence period– Earliness and duration of emergence associated with
increased management difficulty• Facilitated by reduced tillage and POST herb.
– Reduced tillage associated with increased difficulty– POST – no association with management difficulty
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Thank you to all those who reviewed our survey questions and participated in the survey!
Funded by USDA - NCIPM