Post-directing a residual herbicide under five-leaf cotton is not a standard practice in the Mississippi Delta. But it’s something researchers at the Delta Research and Extension Center at Stoneville, Miss., are trying to get a better handle on how Zidua herbicide can be used in the crop.
One of the problems with controlling glyphosate-resistant Palmer amaranth or pigweed is that the soil may lay bare for some time after corn is harvested or cotton laid by, allowing pigweed seed to germinate. A new federal label allows growers to apply Zidua post-directed in cotton.
“We started post-directing at five-leaf, which, for sure, is really small cotton to be post-directing under neath,” says Jason Bond, weed scientist with Mississippi State University who spoke at a field training event conducted by BASF. “We will carry that all the way out to a general layby timing like 15 or 16 nodes.”
Bond says growers post-directing Zidua will encounter some of the same results they’ve seen with other herbicides. “It will be very similar to what you have seen with Valor or Direx,” said Bond. “The leaves it hits, it’s going to burn those off. But once you get some bark on the cotton it will be like with the other products very safe.
“Where I like Zidua as a layby is where we have grass problems. At the (DEREC) station, our second worst problem behind Palmer amaranth is brown top millet. When we start running water down the middles we get big flushes of brown top millet. When that’s out there in the fall our technicians don’t like running their pickers through it.”
Bond says Zidua is much less water soluble than Warrant or Dual. That makes Zidua a good fit for Delta fields, which tend to be furrow-irrigated to a much greater extent than in other regions.
“It’s not going to hang around for the whole season with steadily running water on it every week, but it’s probably going to hang around longer than Dual or, in particular, Warrant,” Bond noted. “I’m basing that on a lot of the trials we’ve done with those three side-by-side in spring applications.”
Because of it solubility, Zidua appears to have a longer residual than Dual and Warrant, and it also has been shown to be more effective on broadleaf weeds, especially the larger-seeded broadleafs.
Bond says researchers have several years of experience with Zidua in corn. “It appears to be a great fit,” he said. “Zidua and atrazine has been very effective in our corn herbicide trials.” For more on Zidua, visit http://www.agproducts.basf.us/products/zidua-herbicide.html.