Project Summaries

12-205  Project Manager: J. M. Reeves


Jason Johnson, Texas AgriLife Extension Service

Workgroup members: James A. Larson, Roland K. Roberts, Dayton M. Lambert, Burton C. English, and Vivian Zhou, University of Tennessee; Kelly J. Bryant, University of Arkansas; Robert J. Hogan, Jr. and Jason Johnson, Texas A&M University; Ashok Mishra, Louisiana State University; Steven W. Martin, Mississippi State University

Weed resistance to herbicides has become a very serious problem for U.S. cotton producers, and weed resistance is spreading across cotton growing regions. Researchers at the University of Tennessee, University of Arkansas, Texas A&M University, and Louisiana State University conducted a mail survey during February and March 2012 to assess the extent of weed resistance in U.S. cotton production, identify practices adopted by cotton producers to manage weed resistance, and evaluate the impacts that resistance has on weed control costs for cotton. The survey was mailed to 2,448 randomly selected cotton growers in 13 cotton producing states. Cotton producers were randomly selected based on county cotton acres, the number of producers in a county, and their distance from counties first reporting resistant horseweed and pigweed between 2000 and 2005. The epicenter counties used to calculate distance from the first outbreaks were Lauderdale County, TN; Edgecombe and Nash Counties, NC; and Macon County, GA. Larger cotton producing counties with more producers that were closer to epicenters were attributed heavier selection probability weights during the random selection of respondents. This targeted sample selection methodology improves the precision of the selection procedure in terms of generating a random list of respondents that were more likely engaged in cotton production and more likely to have been exposed to weed resistance. The response rate was 12.5% (309 usable surveys).

Over two-thirds of cotton producers reported that they had problems with weeds resistant to herbicides. More than 90% of growers indicated that weed resistance to amino acid synthesis herbicides was the problem on their farm. Pigweed was the dominant weed problem and made up 61% of the answers given by growers who indicated that they had weeds resistant to herbicides. Horseweed made up about 24% of the answers given by producers who indicated that they had weeds resistant to herbicides. The remaining weeds reported resistant to herbicides were ragweed (5%) and other weeds (10%). Results also indicated that newly observed infestations of pigweed and horseweed in the sample peaked in 2008-2009 and have declined subsequently. Cotton producers in the sample relied on crop consultants and input dealers the most often to identify weed resistance problems in their fields. On the other hand, growers depended on their fertilizer/chemical dealer and Extension the most often to develop a plan to manage weed resistance. Results also indicated that producers heavily relied on labor intensive practices to control weeds resistant to herbicides in their cotton. For example, 177 of cotton growers used hand hoeing to control resistant weeds on their farms. Half of the producers increased their field scouting. They also relied more on cultural practices such as winter cover crops and crop rotations to control herbicide resistant weeds. Cotton producers to a somewhat lesser extent relied on chemical and mechanical/tillage (e.g., tillage, and hooded sprayers) methods to control resistant weeds. Growers reduced their reliance on Roundup Ready®/Roundup Ready Flex® cotton and increased their use of Widestrike® and Liberty Link® cottons after the onset of weed resistance to herbicides. About 63% of cotton growers who reported weed resistance indicated that they thought that their efforts to manage weed resistance to herbicides were effective or very effective. Results also indicated that the percentage of producers in the sample who indicated that they had cotton total weed control costs of $50 or more per acre about doubled with the onset of weed resistance to herbicides on their farms. About 51% of the farmers who indicated that they did have weed resistance had total cotton weed control costs of $50 or more per acre before resistance was a problem on their farm. By comparison, 91% of farmers indicated that they had total cotton weed control costs of $50 or more per acre after the onset of herbicide resistant weeds on their farms.


Project Year: 2012

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