A new supplemental label allows for Sharpen® herbicide to be applied to mint in Idaho, Indiana, Michigan, Oregon, Washington, and Wisconsin. This registration follows several years of field trials conducted across the Pacific Northwest and Midwest, including research at Purdue University. This research was supported by local mint farmer organizations, the Mint Industry Research Council, and the IR-4 Project. Below I answer some questions about this new registration.
What type of mint can this be used on?
This label is for any Mentha species, including peppermint and spearmint. It can be used on mint harvested for fresh leaves and stems, as well as mint processed into oil.
What type of use is allowed?
Sharpen® can only be applied to dormant, established stands of mint. Established is defined as at least one year after planting. The use rate is 1 to 2 fluid ounces per acre. Sequential applications can be made at least 14 days apart as long as the total in one dormant season does not exceed 2 fluid ounces per acre.
Is an adjuvant needed?
Yes. In our trials we included 2% liquid ammonium sulfate (AMS) and 1% methylated seed oil (MSO). BASF recommends that MSO not be substituted with non-ionic surfactant (NIS).
What is the pre-harvest interval (PHI)?
There is no minimum PHI when applied to dormant mint.
How does Sharpen® work and what weeds will it control?
Sharpen® is a WSSA Group 14 herbicide. It is rapidly absorbed by roots and shoots. Although it can be moved throughout targeted weeds, the symptoms resemble contact herbicide injury, resulting in necrosis (dead plant tissue) within a few days of application.
Targeted weeds are generally winter annuals that emerge in the fall, over-winter, and finish their life cycle the following spring. In the Midwest, this includes chickweed and marestail. We have found it to be highly effective against common winter annual weeds in Indiana (Figure 2 and 3).
Figure 2. Research plots in a peppermint field in Fair Oaks, Indiana in 2021 with no herbicide application. The light green vegetation is a combination of chickweed, small-leaf buttercup, henbit, and marestail. Dark green vegetation is emerging peppermint (Photo by: Stephen Meyers).
Figure 3. Research plots in a peppermint field in Fair Oaks, Indiana in 2021 with 2 fluid ounces per acre of Sharpen® applied during dormancy (right). The light green vegetation is a combination of chickweed, small-leaf buttercup, henbit, and marestail. Dark green vegetation is emerging peppermint (Photo by: Stephen Meyers).
As with any new practice, if you are interested in applying Sharpen® to your mint, we recommend you trial a small area first to know how the application will work in your particular environment.
Where can I find the label?
The label can be viewed here: https://www.cdms.net/ldat/ld99E022.pdf
Or scan this QR code:
