In October 2020, EPA approved five-year registrations (until 2025) for dicamba products including XtendiMax (Bayer), Engenia (BASF) and Tavium (Syngenta) for over-the-top use in Xtend and XtendFlex soybeans. These new dicamba product registrations included national cutoff dates (June 30 in most cases) and mandatory use of additional volatility reduction agents (VRAs) in the tank.
There is no question that dicamba injury across the Iowa landscape in 2020 is the most extensive it has been since the introduction of dicamba in the 1960s. ISUEO field agronomists and commercial agronomists in several areas of the state report nearly all non-dicamba resistant soybean are showing symptoms characteristic of dicamba, and in many fields the injury is fence row to fence row. This is not the type of injury we have observed in the past; it’s at a landscape level.
In this video field agronomist Meaghan Anderson (Iowa State University) discusses the upcoming Crop Advantage Series with local farmer Erik Wibholm from Stratford, Iowa.
http://www.aep.iastate.edu/cas/ In this video entomologist Erin Hodgson (Iowa State University) discusses the upcoming Crop Advantage Series.
I have been reluctant to provide estimates of soybean acres damaged from dicamba applied to Xtend soybean due to the difficulty in developing a realistic number of affected acres. While there has been a significant number of acres damaged by dicamba, I am sure it is less than five percent of Iowa’s nearly 10 million soybean acres. Due to this relatively small number of acres affected (in relation to total soybean acres), dicamba injury will not significantly impact Iowa’s productivity in 2018.
Off-target injury associated with dicamba application in dicamba-resistant soybean was a significant problem in the Cornbelt during 2017 (A final report on dicamba-injured soybean acres). The increase in off-target problems associated with dicamba led to a record number of pesticide misuse investigations by the Iowa Department of Agriculture (IDALS) in 2017.
The Center for Biological Diversity (CBD) recently released a report (A menace to monarchs) describing the threat to monarch butterflies posed by an increased use of dicamba. While I have been fairly critical of the Xtend system1 due to off-target movement of dicamba and subsequent injury, I think CBD has exaggerated the threat to monarchs posed by dicamba.
My colleagues at Purdue recently compiled weather data to determine how many hours would be available to apply the new dicamba products (e.g. Xtendimax with VaporGrip Technology, FeXapan with VaporGrip Technology, and Engenia) postemergence in soybean. Several people asked what the data would look like for Iowa, and as they say, give the people what they want.
As of July 20, the Iowa Department of Agriculture and Land Stewardship (IDALS) had received 142 cases of pesticide misuse, historically this number has ranged from 58-85 at this time of year. Dicamba was involved in 46 of these cases. Two of the dicamba cases involved use in non-crop areas, 10 involved applications on corn and 36 were related to applications to dicamba-resistant soybean (Xtend). The soybean cases were nearly evenly split between Xtendimax w/VGT and Engenia, there were no reports involving products not registered for use on soybean. Cases a
While off-target movement of pesticides is not a new problem, the growth regulator herbicides create a unique situation due to their ability to induce easily observed symptoms at very low doses. Large scale drift problems were experienced when the phenoxy herbicides were introduced in the 1950s. Primitive application equipment and highly volatile ester formulations were largely responsible for these problems. Advances in sprayers and formulations have greatly reduced, but not eliminated, off-target pesticide movement.
