Beltwide Evaluation of the Effect of 2,4-D Drift on Cotton

Wednesday, January 6, 2016: 10:45 AM
Grand Ballroom Acadia (New Orleans Marriott)
Seth A. Byrd , Texas A&M University
Guy D. Collins , NC State University
A. Stanley Culpepper , University of Georgia
Keith L. Edmisten , NC State University
Darrin M. Dodds , Mississippi State University
David L. Wright , University of Florida
Gaylon D. Morgan , Texas A&M AgriLife Extension Service
Paul A. Baumann , Texas A&M University
Peter A. Dotray , Texas Tech University
Andrea S. Jones , University of Missouri
Misha R. Manuchehri , Texas Tech University
Tim L. Grey , University of Georgia
Theodore M. Webster , USDA-ARS
Jerry W. Davis , University of Georgia
Jared R. Whitaker , University of Georgia
John L. Snider , University of Georgia
Phillip M. Roberts , University of Georgia
Wesley M. Porter , University of Georgia
Robert L. Nichols , Cotton Incorporated

Evaluations of cotton exposed to 2,4-D at various growth stages were conducted at 12 locations across the cotton belt during 2013 and 2014.  Two sub-lethal rates of 2,4-D, representing a physical drift scenario (1/421 of the full rate) and a tank contamination scenario (1/21 of the full rate), were applied.  Applications were made at six different growth stages; four leaf (4-lf), 9 leaf (9-lf), first bloom (FB), FB+2wk, FB+4wk, and FB+6wk.  Locations were grouped according to the severity of yield loss compared to non-treated cotton, resulting in three groups each containing four locations.  Group I consisted of locations in which mild yield loss (≤ 15%) occurred, Group II consisted of locations which experienced a moderate yield loss (16 to 25%), while Group III consisted of locations that experienced the most severe yield loss (26 to 40%).  Across the groups, the tank contamination rate was responsible for the majority (74%) of instances in which significant yield loss occurred.  When significant, the drift rate of 2,4-D resulted in yield loss ranging from 19 – 40% compared to non-treated yield.  The contamination rate resulted in yield loss ranging from 16 – 81% compared to non-treated yield.   The greatest magnitude of yield loss occurred when 2,4-D was applied at FB, followed by applications at FB+2 wk and 9-lf.  Visual injury symptoms were evaluated at eight of the locations, however, they did not reflect the severity of yield loss resulting from 2,4-D applications near FB due to the lack of vegetative injury symptoms present.  Plant mapping measurements determined that when significant yield loss occurred, it was primarily a result of a reduction in the number of bolls present on the plant at harvest.  This study suggests that 2,4-D would have the most severe effect on yield when cotton is exposed during growth stages near FB.