We are less than a month away from the cutoff date for approved dicamba product applications in Xtend soybean. We have received several calls recently about the possibility of an extension of this cutoff date in areas of the state that have been hammered by rainfall events and soybean planting dates are delayed.
It is safe to say that the Office of the Indiana State Chemist is very unlikely to change the cutoff date. The reasons for this include the following: First, a large percentage of the off-target movement events in Indiana in 2017, 2018, and 2019 can be traced back to late June and early July applications. Secondly, in 2019 the state of Illinois instituted a dicamba cutoff date, and then delayed the cutoff date because of wet weather.
The result was record numbers of off-target movement events attributed to late June and early July applications. For these reasons, it is not reasonable to expect an extension of the cutoff date for Indiana, and those affected by excessive rains and delayed field operations need to start figuring out what plan B is for these fields.
We hate to say we told you so, but this topic has been covered extensively since this application restriction was announced last winter. The normal spring in the eastern cornbelt is characterized as wet and delayed field operations occur every year in some part of the state unless we have a drought. We repeatedly informed our growers and input provider audiences that one should be prepared for a wet spring and the inability to apply dicamba after June 20th. So, here is a review for those that are in various stages of soybean planting or management of fields that are yet to be planted.
For those fields that have not been planted yet:
- Use a full rate of a residual herbicide that reduces the pressure on the postemergence (POST) herbicide program. Pay particular attention to fields that have waterhemp, and Palmer amaranth and use a preemergence (PRE) residual program that has a group 14 or pyroxasulfone plus another active ingredient that works on ALS and glyphosate-resistant waterhemp or Palmer amaranth.
- Start clean: Don’t plant green into live weed infestations and expect to be able to spray your way out of a mess.
- Plant a soybean variety that has herbicide resistance traits that allow you to use herbicides that don’t have cutoff dates determined by a calendar for control of glyphosate and/or PPO resistant weeds if you think you will have to spray after June 20th.
- For weeds that escape residual herbicides, make timely POST herbicide applications on small weeds and include another layer of a residual herbicide if you have waterhemp or Palmer amaranth.
- Lactofen and fomesafen can also be sprayed POST in those fields where waterhemp and Palmer amaranth populations are still susceptible to PPO-inhibiting herbicides. Lactofen has no rotational restrictions to corn. Fomesafen has a 10 month rotational interval to corn and herbicide carryover may occur for late season applications. Therefore, fomesafen should not be sprayed into the month of July or later if rotating to corn the following growing season.
For fields that have been planted to Xtend soybean varieties:
- As soon as you see some weed emergence, spray your POST treatment so you have time for a follow up treatment before the cutoff date.
- Use a residual with your POST treatment if you have waterhemp or Palmer amaranth.
- Fill in the drowned out areas of the field so you have the crop canopy to compete with weed emergence throughout the summer.
- Lactofen and fomesafen can also be sprayed POST in those fields where waterhemp and Palmer amaranth populations are still susceptible to PPO-inhibiting herbicides. Fomesafen should not be sprayed into the month of July or later if rotating to corn the following growing season due to carryover concerns.