Richard Proost, Nutrient and Pest Management Program, University of Wisconsin-Madison
Investigations of soybean leaf puckering in Wisconsin have often found the injury was caused by dicamba–a plant growth regulator (Group 4) that is prone to drift and commonly used in corn herbicides (i.e., Banvel, Clarity, Distinct, NorthStar, Status, Sterling Blue, Yukon).
In 2017, dicamba-tolerant (DT) became available to U.S. farmers along with three new restricted use dicamba products for use on DT soybean–Engenia, FeXapan, and Xtendimax. Although this represents a step forward in weed management and reducing injury and reducing injury in some soybean fields, it also potentially increases dicamba use and therefore the likelihood of injury to non-DT soybean and other dicamba -susceptible plants in nearby fields. Other than misapplying dicamba to a non-DT soybean field, there are four common ways that dicamba can reach fields and cause injury:
- Spray particle drift
- Vapor drift
- Application during a temperature inversion
- Contaminated spray solution
Understanding how these work and how to reduce their incidence, along with being able to differentiate between true dicamba injury symptoms and those that mimic dicamba injury will help increase responsible dicamba use.