Project Details:

Title:
Investigating dicamba movement and injury to soybean

Parent Project: Investigating dicamba movement and injury to soybean
Checkoff Organization:Missouri Soybean Merchandising Council
Categories:Weed control
Organization Project Code:407-19
Project Year:2019
Lead Principal Investigator:Kevin Bradley (University of Missouri)
Co-Principal Investigators:
Mandy Bish (University of Missouri)
Keywords: herbicide injury

Contributing Organizations

Funding Institutions

Information and Results

Click a section heading to display its contents.

Project Summary

The objectives of this research are 3-fold: (1) Correlate field-scale observations of dicamba injury to real­-world yield losses so that producers and agrichemical industry representatives are better prepared to deal with future office-site dicamba injury issues; (2) Study the impact of dicamba formulations on
temperature inversions; and (3) Initiate development of a mobile app and/or website that will send alerts to herbicide applicators when unfavorable weather conditions are present.

Project Objectives

Project Deliverables

Progress of Work

Updated April 27, 2021:
Several million acres of U.S. soybean were injured by off-target movement of dicamba in 2017 and 2018, and state departments of agriculture collectively investigated more than 4,000 dicamba-related soybean injury claims in the past two seasons alone. In many incidences, the cause(s) of dicamba movement have been identified as factors related to physical drift (wind speed, improper nozzles, boom height, etc.), but in other instances further investigations have revealed that label guidelines were followed yet off-target movement of dicamba still occurred. The primary objectives of this research were to 1) determine the effects of time of application, weather conditions and new formulations on the concentration of dicamba detected in the air following application, and 2) assess weather and environmental factors surrounding dicamba applications in order to identify any consistencies that may explain off-site dicamba movement.

Through this research, the team has been able to determine that dicamba can be detected in the air for as many as 96 hours following an application of either Xtendimax or Engenia, although highest dicamba air concentrations typically occur within the first 8 hours after application.

Highest dicamba concentrations have consistently been detected during the night following an application made in either the evening or afternoon, however “peaks” in dicamba air concentrations have also been commonly detected in the
afternoon following an evening application. Results from this research also indicate that the concentration of dicamba
in the air is highly influenced by atmospheric stability (i.e., surface temperature inversions) and other variables such as
temperature and relative humidity.

Our findings from this air sampling research led us towards the establishment of a real-time inversion monitoring network (mesonet.missouri.edu), and an additional project in which researchers conducted a statistical analysis of the weather conditions surrounding approximately 200 commercial, field-scale successful and unsuccessful dicamba applications. This analysis led to the identification of several environmental factors that are likely to increase the likelihood of off-target movement of dicamba, including:
1 lower soil pH
2 increase in maximum dew point temperature the day of application
3 increase in maximum wind speed the day after application
4 proximity to larger bodies of water.

As a result of this analysis, in 2018 the team conducted two field research experiments to confirm the results from the statistical weather analysis pertaining to the effects of soil pH on off-target movement of dicamba. Results from both experiments indicate that greater dicamba volatility occurred in response to lower soil pHs (<6.8), and that soybean injury as a result of dicamba volatility was similar Air sampler used to detect dicamba air from Engenia and Xtendimax.

Final Project Results

Benefit to Soybean Farmers

Performance Metrics

Project Years