By Brian Hefty
As a farmer, I love when our input costs keep coming down. A good example is the Group 15’s. For soybeans, these include Dual, Warrant, Zidua, Outlook, and some generics. In my opinion, the best way to use these herbicides is early post, in combination with a contact herbicide like Roundup. These products are not nearly as effective at controlling weeds as the 3 pre’s (yellow plus metribuzin plus PPO), but they can definitely add mid- to even late-season residual control, and that could be extremely important in your weediest fields.
Extending residual – or overlapping residuals, as it is otherwise known – is more important in the south than in the north because the growing season is much shorter and there are far fewer resistant weeds in the north. Even so, if you’ve got a really weedy field, adding one of these Group 15’s for $4 to $8 per acre could add several bushels to your yield AND reduce the weed seed bank for future crops. The Group 15’s have zero contact activity, so don’t count on any control of emerged weeds, but do expect some suppression for a month or more after application on grass, lambsquarters, waterhemp & all pigweed species, kochia, and other tough, Roundup-resistant weeds.
There are several premixes that contain a Group 15 and another herbicide, so these are obviously great choices, too. For example, Anthem Maxx, and Warrant Ultra each contain a PPO and a Group 15. Anthem Maxx contains the active ingredients (ai) found in Zidua (Group 15) and Cadet (PPO). Warrant Ultra features the ai’s from Warrant/Harness (Group 15) and Flexstar (PPO).
Again, as long as you have 3 pre-emerge modes of action down and low to moderate weed pressure, adding a residual post-emerge probably isn’t necessary. On the other hand, if you didn’t use 3 pre’s early or if you have heavy weed pressure, we would absolutely encourage you to get a Group 15 out there early post.