New weed technology for resistance

One factor is common to new weed control technologies coming onto the market for corn and soybeans — most can help with resistant weeds.

“A lot of the impetus for companies to continue to develop new herbicide technology into corn and soybeans is the resistance management issue,” said Angela Thompson McClure, corn and soybean specialist at the University of Tennessee, at a recent grain and soybean conference in Dyersburg, Tenn.

New products include herbicide resistance traits as well as chemical control products and mixes. One thing to remember is that weed control is now a little more complicated than it was a few years ago. Here’s a look at some of the new products and where Thompson-McClure thinks they fit in weed control.

LibertyLink soybeans — A new technology available in 2009 which allows for Ignite herbicide to be applied over-the-top. “Unfortunately, seed supply is short, and just a few seed companies are handling the technology. There is not a lot of information on variety performance, but we are trying to get a couple of LibertyLink varieties in the country tests.

“Ignite is not a magic herbicide, but it has particularly good fit for weeds that are resistant to glyphosate. It has broad-spectrum weed control, controls resistant horseweed and resistant Palmer pigweed. It does have some weaknesses on grasses and larger-size weeds. It works very well if there is a residual pre-emergence herbicide applied in front. We also must target small weeds — 3-inch weeds are the ideal size to make the system effective.”

Originally, the recommended rate for Ignite on LibertyLink soybeans was 22 ounces per application. The problem was that the recommended rate for resistant horseweed was 29 ounces. Today, “if you’re dealing with smaller, non-problem weeds and you get the herbicide out early, you can make two 22-ounce, in-season applications. If you’re looking at resistant horseweed, you have the option of using the higher rate of 29 ounces and up to 36 ounces applied in a single year.

“A residual definitely helps versus relying on Ignite alone as a post-emergence stand-alone product,” Thompson McClure said. Studies have shown that Ignite followed by Ignite without a residual did not hold up well.”

For LibertyLink soybeans, the University of Tennessee recommends a standard burndown program of glyphosate or Gramoxone with Clarity, followed by a residual product. “We have lots of good choices for pre-emergence products such as Valor, Sencor, Dual and Authority, if you’re not worried about rotating back to cotton.”

When applying Ignite, “Try to get it out as early as possible,” McClure said. “There is a size limitation with this product. We really want to go with small weeds as early as possible.”

Authority MTZ — from FMC, is a pre-mix of Authority and Sencor for soybeans. “It provides residual broadleaf weed control and helps a little bit on grasses,” Thompson McClure said. “We’re also looking at it for horseweed, pigweed and other broadleaf weeds. The use rate is 12 ounces to 20 ounces on soils that have less than 1 percent organic matter. It works very well if you’re not thinking about going back into a cotton rotation.”

Envive — from DuPont, is a three-way mix of Classic, Harmony and Valor. “It is a pre-emergence product with broad spectrum activity. It’s a good horseweed product and the Valor really helps with the pigweed. The rate is 2.5 ounces to 4 ounces per acre.”

Laudis — a new bleaching herbicide for corn from Bayer, “is similar to Callisto in mode of action. It provides post-emergence control for broadleaves and has good activity on seedling johnsongrass. The use rate is 3 ounces per acre. It’s also labeled on sweet corn and popcorn.”

Impact– the standard rate for Impact, marketed by AMVAC, is 0.750 ounce. Impact, can be applied up to 45 dates before harvest. Impact is weak on morningglories and cockleburs. Impact can be tank-mixed with glyphosate on Roundup Ready corn.

Callisto — the standard rate for Callisto, from Syngenta, is 3 ounces. Callisto can be applied post-emergence up to 30-inch corn. Callisto is weak on morningglories and cockleburs. Callisto can be tank-mixed with glyphosate on Roundup Ready corn.

Resolve Q is Resolve plus Harmony and a safener. “It can be tank-mixed with glyphosate for application on Roundup Ready corn in a post-emergence application for residual on grasses and broadleaves. It does need atrazine to extend the residual for weeds like Palmer pigweed. The rate is 1.25 ounces, which is a little higher than the old Resolve rate. It can be applied over-the-top of corn up to seven collars. “

Status, from BASF, “has a good fit on giant ragweed. It’s a Clarity synergist, safener combination. You get the weed control of Clarity, but the safener gives you a little wider window for corn. The use rate is 5 ounces to 10 ounces at 36-inch or V-10 corn. If you had to use Clarity on ragweed that was a little tougher to control, you’re limited to 8-inch corn.”

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TAGS: Soybeans
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