On Wednesday, June 3, the Ninth Circuit Court of Appeals in San Francisco issued a decision that nullifies the current labels for Engenia, FeXapan, and XtendiMax herbicides. The decision was in response to a 2017 lawsuit stating that the EPA understated the risks of using the products. There are a lot of questions about the consequences of this decision and few answers at the moment. We are in a position where we must wait for the legal process to play out and for the EPA to issue clear guidance. What we do know at the present time is that the court order makes applications of Engenia, FeXapan, and XtendiMax illegal. However, the current statement from the Kansas Department of Agriculture is that these products are still available for use in Kansas.
This is a season where weed management activities are essential and decisions must be made quickly. Some of the best alternatives to dicamba will be products containing Group 14 herbicides such as fomesafen (Reflex, FlexStar). A list of these products is presented in Table 1. Weed size and spray coverage will be important factors affecting control by these products. Also, consider that dicamba does have some residual activity that you may want to replace and is important for control of difficult weeds like Palmer amaranth. Group 15 herbicides containing active ingredients such as metolachlor or acetochlor will be the likely candidates for this purpose. These products are also listed in Table 1.
Table 1. Herbicide alternatives to dicamba for post-emergence control of broadleaf weeds in dicamba-tolerant soybean.
|
Herbicide |
Group |
Active ingredient (s) |
Comments |
|
Classic |
2 |
chlorimuron |
Many pigweed populations are resistant |
|
Cobra, others |
14 |
lactofen |
Expect crop injury |
|
Dual II Magnum, others |
15 |
S-metolachlor, metolachlor |
Apply through V3 |
|
FirstRate |
2 |
cloransulam |
Many pigweed populations are resistant |
|
Flexstar GT |
14 + 9 |
fomesafen + glyphosate |
Expect crop injury 10-month rotation to corn Regional application restrictions |
|
Flexstar, Reflex, others |
14 |
fomesafen |
Expect crop injury 10-month rotation to corn Regional application restrictions |
|
Marvel |
14 + 14 |
fluthiacet + fomesafen |
Apply before full flower soybean Expect crop injury |
|
Outlook |
15 |
dimethenamid-P |
Apply before V5 |
|
Prefix |
14 + 15 |
fomesafen + S-metolachlor |
Expect crop injury 10-month rotation to corn Regional application restrictions |
|
Pursuit |
2 |
imazethapyr |
Many pigweed populations are resistant |
|
Raptor |
2 |
imazamox |
Many pigweed populations are resistant |
|
Storm |
14 + 6 |
acifluorifen + bentazon |
Expect crop injury |
|
Synchrony |
2 + 2 |
thifensulfuron + chlorimuron |
Many pigweed populations are resistant |
|
Tavium |
4 + 15 |
dicamba + S-metolachlor |
Apply through V4 or 45 days after planting |
|
Ultra Blazer, others |
14 |
acifluorifen |
Expect crop injury |
|
Warrant |
15 |
acetochlor |
Apply before R2 soybean |
|
Warrant Ultra |
14 + 15 |
fomesafen + acetochlor |
Apply before R2 soybean 10-month rotation to corn Regional application restrictions |
|
Zidua |
15 |
pyroxasulfone |
Apply through V6 |
We will share any updates to this decision as more information and guidance becomes available in the coming days.
Sarah Lancaster, Extension Weed Science Specialist
slancaster@ksu.edu