It recently has come to my attention the the POST application soybean label for Prefix has changed from what is currently printed in the 2015 UGA Pest Control Handbook (Page 579). Not really sure what happened but I will take the full blame for not catching this earlier. The old Prefix label reads as follows:
"Prefix herbicide may be applied at 2-2.33 pt/A as a postemergence application from cracking through the third trifoliate stage of soybeans (V3). "
The new label reads as follows:
"Prefix herbicide may be applied at 2-2.33 pt/A as an early postemergence application in soybeans."
According to my Syngenta contacts, the main purpose of this label change was to remove the 3rd trifoliate restriction.
In order to clear up any confusion caused by this label change, I would recommend that any product that contains the active ingredient fomesafen (Dawn, Flexstar GT, Prefix, TopGun, Reflex) be applied on or after the V1 stage of growth (Figure 1). Although it would be unlikely for earlier applications to cause significant crop injury, a soybean plant in the V1 stage will be better able to tolerate and recover from the the injury caused by fomesafen (Figure 2). Since fomesafen is a contact herbicide, only the soybean leaves that are present at application will be injured.
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| Figure 1. V1 soybean stage of growth. |
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| Figure 2. Roundup + Reflex + Dual Magnum applied to soybeans in the VC stage of growth @ 2 DAT (Photo courtesy of Eddie McGriff - Southern States) |
