Federated recommends herbicide programs designed around the problematic weeds, and "more often than not, we are seeing waterhemp and giant ragweed together," said Kevin Carlson, Federated's senior agronomist.
Carlson said, "From a pre-emerge standpoint, we have to ask what works on both [waterhemp and giant ragweed?"
Bryan Thompson of Rosen's said, "Blanket® 4F is a liquid straight goods sulfentrazone product that's one of the best pre-emerge active ingredients on the market for waterhemp." In the fight against giant ragweed, Blanket 4F tank mixed with Sonic® or Authority® First can be an effective choice. Thompson said this "agronomically sound" tank mix offers "considerable savings to the grower" when both weed species are present.
"Blanket 4F is comparable in formulation to FMC's Spartan® 4F, and it works well as a supplement to Sonic and other popular pre-emerge herbicides," Thompson said.
A tank mix of 2 oz./ac. of Blanket 4F with 3 oz./ac. of Sonic or Authority First offers about the same amount of sulfentrazone as 5 oz./ac. of Sonic, but at a lower cost -- and this mix offers residual control of both waterhemp and giant ragweed. Thompson said, "As a rule of thumb, every 1 oz./ac. of Blanket will add approximately one week of additional residual control." Carlson added that there "is no additional benefit to go with the higher rate of Sonic for giant ragweed."
For a broader spectrum of control -- in the absence of giant ragweed -- growers can choose Blanket 4F on its own, or with a variety of other combinations, such as Blanket 4F tank mixed with Sencor, Dual, or Outlook (or their generic/private label versions). These options provide "two modes of action to control waterhemp and many other small-seeded broadleaves," said Thompson.
The photo at right, taken by last summer by Thompson in St. Peter, MN, shows soybeans (in a field with waterhemp and giant ragweed pressure) 50 days after a pre-emerge application of Sonic plus Blanket 4F at 3 oz./ac. each -- with no post treatment or burner product applied.
It's not too early to discuss tough weed control options for 2017. Contact your Federated Agronomist to design a program that fits your specific weed issues.