Cotton response to preplant applications of 2,4-D and dicamba

Authors: PRICE, KATLYN - Auburn University; LI, STEVE - Auburn University; LEON, RAMON - North Carolina State University; Price, Andrew

Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2019
Publication Date: 9/10/2019
Citation: Price, K., Li, S., Leon, R., Price, A.J. 2019. Cotton response to preplant applications of 2,4-D and dicamba. Weed Technology. 34:1 pp. 96-100. https://doi.org/10.1017/wet.2019.98.
DOI: https://doi.org/10.1017/wet.2019.98

Interpretive Summary: Weed control programs used prior to planting cotton in the southeast frequently include 2,4-D and dicamba for control of herbicide resistant weeds and other problematic weed species. Sensitive cotton varieties planted into soil treated with 2,4-D and dicamba utilized in burndowns can result in crop stunting and stand loss if use rate is too high and the plant back interval is too short. The objective of this study was to evaluate cotton stunting and yield responses resulting from 2,4-D and dicamba residues in the soil after preplant burndown applications. While stand losses were observed in both years, there was no yield loss at harvest. Our data suggests growth stunting and stand reduction may occur if susceptible cotton varieties are planted too close to a burndown application with 2,4-D and dicamba, but final yields may not be affected after a full growing season. Dicamba showed greater potential to cause growth stunting and stand reduction than 2,4-D.

Technical Abstract: Burndown programs for cotton in the southeast frequently include 2,4-D and dicamba for control of herbicide resistant weeds and other problematic weed species. Sensitive cotton varieties planted into soil treated with 2,4-D and dicamba utilized in burndowns can result in crop stunting and stand loss if use rate is too high and the plant back interval is too short. The objective of this study was to evaluate cotton stunting and yield responses resulting from 2,4-D and dicamba residues in the soil after preplant burndown applications. Treatments of 2,4-D included 532 and 1063 g ae h-1 applied 3 weeks before planting and 53, 160, 266, 532, 1063 g ae h-1 applied at planting. Treatments of dicamba included 560 and 1120 g ae h-1 applied 3 weeks before planting and 56, 168, 280, 560, 1120 g ae h-1 applied at planting. 2,4-D and dicamba treatments applied 3 weeks before planting did not have any adverse effects on cotton stand, plant height, or yield. 560 g ae h-1 of dicamba applied at planting significantly (P=0.05) reduced cotton stand by 36% at 21-24 days after planting (DAP) over all locations in 2016. In 2017, stands were reduced by dicamba at 168, 280, 560 and 1120 g ae h-1 by 17-25% at 20-23 DAP. Moreover, cotton stand was not affected by 2,4-D in 2016, and only 266, 532, and 1063 g ae h-1 of 2,4-D caused stand reductions of 26-36% at 20-23 DAP over all locations in 2017. Dicamba at 560 g ae h-1 at planting was the only treatment in this study that reduced plant height (27% and 38% at 21-24 DAP and 50-51 DAP respectively, in Macon County in 2016). While stand losses were observed in both years, there was no yield loss at harvest. Our data suggests growth stunting and stand reduction may occur if susceptible cotton varieties are planted too close to a burndown application with 2,4-D and dicamba, but final yields may not be affected after a full growing season. Dicamba showed greater potential to cause growth stunting and stand reduction than 2,4-D.