Tough, herbicide-resistant weeds are a familiar obstacle for corn and soybean growers in southern IA. Waterhemp, giant ragweed, marestail (horseweed) and morningglory are common throughout the region, and herbicide resistance has been an evolving problem since the widespread use of ALS inhibitors in the late 1980s. Today, it’s not unusual for a single field to have several different types of weed pressure and varying types of herbicide resistance. To complicate matters further, weeds like waterhemp have developed resistance to multiple different sites of action (SOAs).
So, what’s the most effective approach to weed control and resistance management? The best strategy is to use corn and soybean herbicides with multiple effective SOAs, specifically targeted to your problem weeds, and overlapping residuals. Multiple effective SOAs ensure you are attacking problem weeds from different points of vulnerability and not selecting for resistance, while using overlapping residuals helps keep fields clean through canopy and beyond.
To demonstrate the effectiveness of herbicides with multiple effective SOAs and overlapping residuals, we set up several trials at our Yarmouth, IA, Grow More™ Experience site. The corn herbicide bare-ground trial was treated with a preemergence application on May 2, and a post-emergence treatment was made on June 1. The in-crop soybean herbicide trials were planted and treated with a preemergence application on May 3, and then a post-emergence treatment was made on June 2.
Watch as Agronomic Service Representative Zachary Trower talks through the trials, or check out a few pictures below:
Here’s what we saw in our corn herbicide bare-ground trial:
A bare-ground trial shows results from a 2-pass application ofAcuron®corn herbicide. A foundation rate of Acuron (1.5 qt/A) was applied preemergence with atrazine (1 pt/A) and glyphosate (22 fl oz). It was followed post-emergence with the remaining rate of Acuron (1.5 qt/A) plus atrazine (1 pt/A) and glyphosate (32 fl oz). Picture taken 68 days after initial treatment.
Here’s what we saw in our in-crop soybean herbicide trial:
Boundary® 6.5 EC(2 pt/A) applied preemergence followed byPrefix®(2 pt/A) and Liberty® 280 SL (32 fl oz/A). Photo taken 67 days after initial treatment.
BroadAxe® XC(30 fl oz/A) applied preemergence followed by Prefix (2 pt/A) and Liberty 280 SL (32 fl oz/A). Photo taken 67 days after initial treatment.
Prefix (2.5 pt/A) applied preemergence followed byTavium® Plus VaporGrip® Technology(56.5 fl oz/A) and glyphosate (32 fl oz/A). Photo taken 67 days after initial treatment.
For corn, we recommend Acuron herbicide. Acuron has 4 active ingredients, including the Syngenta-exclusive active ingredient, bicyclopyrone, and 3 effective SOAs. It’s the only corn herbicide that delivers 5-15 more bushels an acre when used preemergence at the full labeled rate.* In a 2-pass program, a foundation rate of Acuron can be followed by the remaining rate post-emergence or an application of Halex® GT plus either an atrazine or dicamba for an additional SOA. Calculate the extra revenue potential you could find next season with Acuron.
In soybeans, we recommend a preemergence application of Boundary 6.5 EC, BroadAxe XC or Prefix herbicides followed by a post-emergence application of Flexstar® GT 3.5 herbicide or Tavium Plus VaporGrip Technology herbicide in dicamba-tolerant soybeans. Prefix is also a post-emergence option if it wasn’t used as the preemergence application. All of these programs include multiple effective SOAs for control of tough weeds through canopy and beyond.
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Performance assessments are based upon results or analysis of public information, field observations and/or Syngenta evaluations.
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*Acuron yield advantage range based on 2016 Syngenta and university trials comparing Acuron to Corvus®, Resicore®, SureStart® II and Verdict® applied preemergence at full label rates.