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Delaware Soybean Grower Survey on Glyphosate-resistant Horseweed (Conyza canadensis)

Published online by Cambridge University Press:  20 January 2017

Barbara A. Scott  and
Mark J. Vangessel
Barbara A. Scott*
Affiliation:
Department of Plant and Soil Science, Research and Education Center, University of Delaware, 16483 County Seat Highway, Georgetown, DE 19947
Mark J. Vangessel
Affiliation:
Department of Plant and Soil Science, Research and Education Center, University of Delaware, 16483 County Seat Highway, Georgetown, DE 19947
*
Corresponding author's E-mail: [email protected]
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Abstract

In November 2004, a 29-question survey was mailed to Delaware soybean growers to determine grower perceptions of glyphosate-resistant (GR) horseweed and if glyphosate applications, GR soybean usage, and management practices had been altered in lieu of the presence of resistance. A total of 213 valid responses were received. Ninety-eight percent of respondents reported planting GR soybean at some point in the last 5 yr, with 90% reporting having planted GR soybean 3 or more years. The presence of GR horseweed on-farm was reported by 38% of the respondents and 95% of those growers with GR horseweed on-farm reported implementing one or more changes in GR soybean management. The most frequent change (66% of growers) due to resistant horseweed was the application of another herbicide with a different mode of action before planting. Forty-eight percent of growers with resistance on-farm reported a $5 to $17/ha increase to manage for GR horseweed, with 28% reporting a greater than $17/ha increase. Regardless of experience with GR horseweed, approximately 80% responded that it was worthwhile to incur additional costs now to preserve glyphosate for future use. Soybean grower reliance on glyphosate has not decreased in light of GR horseweed in Delaware. Misconceptions of timing for the selection of GR horseweed biotypes and the future availability of new herbicides with different modes of action exist within the farming community.

Keywords

Glyphosatehorseweed, Conyza canadensis (L.) Cronq. ERICAsoybean, Glycine max (L.) MerrGlyphosate-resistant soybeanglyphosate-resistant horseweedsurvey
Type
Extension/Outreach
Information
Weed Technology , Volume 21 , Issue 1 , March 2007 , pp. 270 - 274
Copyright
Copyright © Weed Science Society of America 

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