By Dr. Mark Loux
Following a summer of many instances of off-target movement of dicamba across the country from use in Xtend soybeans, the labels for Engenia, XtendiMax, and FeXapan were modified in an attempt to reduce future problems. These products became restricted use pesticides, and an additional requirement is that anyone applying these products must attend annual dicamba or group 4 herbicide-specific training, and have proof that they did so. Details are still being worked out on this training for Ohio, but it will not be conducted by OSU Extension, or accomplished through OSU winter agronomy or pesticide recertification meetings. At this point, as far as we know it appears that it will be conducted by Monsanto, BASF, and DuPont at meetings held specifically by them for this purpose, and also possibly through an online training module. Final details and meeting schedules are not likely to be in place until after the first of the year. We will pass on information as we get it from ODA and companies, and applicators will undoubtedly receive this information from multiple other sources as well.
OSU, Purdue, and U. of Illinois have put together a fact sheet on stewardship of dicamba, which is available here, or at our website – u.osu.edu/osuweeds. This is not meant to be an all-inclusive list of application requirements from labels, but it also contains some suggestions on stewardship that are not part of labels. Unlike the three companies selling these products, whose position is that applicator error was responsible for most off-target problems in 2017, university weed scientists concluded that volatilization of dicamba caused many of them. And we are not convinced that the label changes adequately address the potential for volatilization to occur, or provide conservative enough guidelines to help applicators assess how and where (and more important – where not) to apply dicamba in Xtend soybeans. OSU’s position on the use of dicamba in Xtend soybeans has not changed over the past year. We feel that off-target problems could be greatly minimized by restricting dicamba use to early-season, as a component of no-till burndown treatments. Dicamba has utility for control of marestail in the burndown, and there is just less emerged vegetation to damage earlier in the season should off-target movement occur. This is not to say there is no risk of movement or damage when used early-season. Just because risk to non-Xtend soybeans or other crops is low because they have not emerged yet, does not mean there is not risk to nearby fruit trees, vegetables, ornamentals, etc. However, postemergence use of dicamba accounted for most of the off-target problems in 2017, and we would expect a similar trend in 2018.