Evaluation of Glyphosate Resistant Giant Ragweed (Ambrosia trifida) in Ohio Soybean (Glycine max) Fields

<p>Studies were conducted in 2011 and 2012 to evaluate glyphosate resistant giant ragweed in Ohio soybean (Glycine max) fields. Specific objectives were as follows: 1) Determine the spatial distribution and incidence of giant ragweed (Ambrosia trifida) infestations in Ohio soybean fields at the end of the growing season; 2) Characterize the response of Ohio giant ragweed populations to foliar application of glyphosate and cloransulam-methyl; 3) Determine the effect of postemergence herbicide management strategies on control and fecundity of giant ragweed in glyphosate-resistant soybeans and 4) Compare the effectiveness of University-recommended strategies with those used by growers, for management of giant ragweed.</p><p> Driving surveys were conducted in 2011 and 2012 to determine spatial distribution of giant ragweed infestations across the state of Ohio. Infested fields accounted for approximately 4% of fields surveyed, and occurred in 50 to 67% of counties surveyed. Results of the surveys indicated that giant ragweed infestations were localized occurrences, spread throughout the state. Infested counties appeared to be distributed in north-central and west-central Ohio. Greenhouse dose response screens were conducted to determine levels of herbicide resistance in giant ragweed from across Ohio. Giant ragweed population response to glyphosate indicated that the distribution of populations among mortality classes differed depending on the application rate of glyphosate. Differences in the distribution of populations across plant mortality categories demonstrated that giant ragweed with low levels of glyphosate resistance in Ohio are likely to be controlled by glyphosate applied at high rates. Distribution of populations across biomass reduction classes was similar. A greater proportion of the populations surveyed were distributed in the 80 to 100% biomass reduction class when glyphosate was applied at 3.3 kg ae/ha compared to the 0.84 kg ae/ha rate. Giant ragweed response to cloransulam was variable within and between populations. Lack of distribution differences across plant mortality categories in response to cloransulam application indicated that cloransulam-resistant giant ragweed has similar levels of resistance to both high and low rates of application. A similar response was obsereved for giant ragweed growth after application; within biomass reduction categories, both cloransulam rates had approximately equal numbers of populations in each category. </p><p> Comparisons of grower and University control of giant ragweed took place during field studies conducted in 2011 and 2012. Control of giant ragweed through University treatments was best with two herbicide applications compared to single application treatments. Grower control of giant ragweed was lower than all university treatments due to delays in herbicide application. Multiple postemergence applications lowered giant ragweed survival at harvest, compared to single postemergence treatments. Giant ragweed fecundity was lower in treatments two postemergence herbicide applications compared to single postemergence treatments. In order to effectively control giant ragweed throughout the growing season, multiple postemergence herbicide applications must occur to control multiple flushes of giant ragweed seedlings during the season.</p>

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Horticulture and Crop Science

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Bethel, James D.

Contributors dc:contributor

• Loux, Mark

• Agriculture
• Agronomy
• Giant Ragweed (Ambrosia trifida)
• Glyphosate resistant
• Soybean (Glycine max)

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1357292715

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1357292715