2023
Factors influencing grass control with glyphosate and dicamba tank mixes in dicamba
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Contributor/Checkoff:
South Carolina Soybean Board
Category:
Sustainable Production
Keywords:
AgricultureCrop protectionHerbicide
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Michael Marshall, Clemson University
Co-Principal Investigators:
Project Code:
Contributing Organization (Checkoff):
South Carolina Soybean Board
$13,148
Institution Funded:
Clemson University
$13,148
Brief Project Summary:
This research project seeks to determine the factors contributing to decreased grass control from tank mixtures of dicamba and glyphosate. That has been the predominate postemergence combination for weed control in dicamba-tolerant crops since 2017. However, farmers are reporting unsatisfactory weedy grass control. Glyphosate labels recommend using flat fan nozzles that produce small to medium droplets for optimum coverage. However, dicamba labels require nozzles that produce very large, coarse droplets that minimize particle drift potential. These nozzles can reduce coverage of weedy grasses compared to finer droplet nozzles because grass leaves tend grow vertically with narrow leaves. Plus, the herbicide chemistries can reduce or antagonize grass efficacy, regardless of nozzles.
Key Beneficiaries:
#agronomists, #extension agents, #farmers
Unique Keywords:
#dicamba, #glyphosate, #herbicide, #weed control
Information And Results
Project Summary

Glyphosate plus dicamba has been the predominate postemergence combination for weed control in dicamba-tolerant cotton since 2017. However, unsatisfactory weedy grass control in cotton after applications of glyphosate and dicamba have been reported. Historically, glyphosate alone provides excellent postemergence control of grasses, such as Texas panicum, goosegrass, and broadleaf signalgrass. Glyphosate product labels recommend using flat fan nozzles that produce small to medium droplets for optimum coverage. However, dicamba product labels require the use of nozzles that produce very large, coarse droplets which minimizes the potential of particle drift during application. These larger droplet nozzles can reduce coverage of weedy grasses compared to the finer droplet nozzles because grass leaves tend to have a vertical growth orientation with narrow leaves. In addition, loss of coverage, tank mixing dicamba (or any other
growth regulator type herbicide) with glyphosate can reduce or antagonize grass efficacy (regardless of the nozzle type selected). Therefore, this research project seeks to determine the factors contributing to decreased grass control from tank mixtures of dicamba and glyphosate in cotton.

Project Objectives

1. To determine factors reducing annual grass control in cotton with glyphosate and dicamba tank mixtures.
2. To disseminate these research results to South Carolina soybean growers through field days and Extension meetings.

Project Deliverables

1. 4 quarterly and 1 final report to the SC soybean board (Feb 7)
2. Present results to soybean growers at county and/or regional Extension cotton meetings winter of 2023.
3. Present results at the 2024 Southern Weed Science Society Meeting

Progress Of Work

Final Project Results

Benefit To Soybean Farmers

We will measure success in this project by showing the impact of different nozzles, spray volume, and tank mixtures with dicamba on grass weed control in dicamba tolerant soybean. This information will be used by farmers to reduce grass control failures in the future.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.