Two-pass program

Two-pass program

David Sparks Ph.D.
David Sparks Ph.D.
When tough weeds are invading your fields, you don’t just need one line of defense since weeds can germinate all season long and steal vital nutrients and water from your crop. Jason Snell is an agronomy service representative for Syngenta. He talks about the importance of controlling early-season weeds to protect overall ROI.

“Early-season weeds can reduce fertility, take up fertility for your crop in the weed biomass, thereby not making it available to your crop. With fertilizer prices where they are, we need to make the most of every bit of fertilizer we put down, so, early season weeds can be a problem there. Also, some areas have been very dry, so early-season weed pressure can be a high user of soil moisture, so that water limitation from early season weed pressure can also inflict yield penalties later on in the year. There's been some well-researched and well-known reactions to early season weed pressure in corn. It changes the profile of the corn, how it grows, and in its nature, both from above- and below-ground results.”


Effective weed management throughout the season sets corn fields up for success now and in the years to come. He says the best way for growers to achieve optimal weed management is with an overlapping residual herbicide program.

“Overlapping residual management consists of a good, solid residual pre-emerge, and then coming in with a post in your two-pass system before that weed pressure has emerged. The best time to kill a weed is before it's out of the ground, and that would lead you to overlapping that residual. It can be a strange feeling to some growers, especially growers that have had a lot of experience in a Roundup system over the last 20 years, where you can kill some pretty large weeds after they come out of the ground. Those weeds that have emerged and that have put on any biomass at all are reducing the availability of nutrients and water to that crop. It also leads to more resistance pressure if those weeds are emerged. Pre-emerge applications of residuals as well as overlapping those residuals before the weed seed bank can take off and get out of the ground reduces that resistance issue and also keeps the nutrients available for your crop.”


Snell talks about his recommendation for a program that will provide season-long protection.

“Our newest one containing an Acuron® GT pass post can be paired with several of our products pre-emerge and go from a Lumax® or Lexar situation as a pre-emerge foundation application. We also have Bicep brands, or Straight Dual Magnum® pre-emerge. They have different strengths, different price points to fit almost every application you need out there and every situation that varying fields within a grower’s portfolio can be required of. We like foundation rates of Lumax down, containing Callisto®, Atrazine, and S-Metolachlor or Dual following that at early pre-emerge, again, before weed emergence, to overlap that residual with Acuron GT post-Emerge.”


Snell discusses the benefits of using Acuron-GT for ultimate post-emergence weed control.

“Acuron GT contains four products: the Callisto that we've had really good experience with and good consistent control over the years;  S-Metolachlor or Dual, which is our long residual for grasses and small-seeded broadleaf; glyphosate in the tank with Acuron GT, and the new product we added was bicyclopyrone, an HPPD we've had on the market for a few years. This is our first post-focused application of bicyclopyrone, again, HPPD family similar to mesotrione or Callisto, but it has some different properties that lead to a really nice layering of benefits between those two HPPDs. Callisto sets up in a thin layer on top of the soil and is released with subsequent rainfalls after application. Bicyclopyrone sets up in the soil and moves down the soil profile with each rain and continues to move down to catch large-seeded broadleaf and some grasses when they germinate down in the soil. So, deeper in the soil, two to three inches down, they get a dose of this HPPD, and it leads to greater control of pre-emerge weeds across a broader spectrum.”


To learn more about the benefits of a two-pass herbicide program that includes Acuron GT, visit or talk to your local Syngenta retailer. And remember to always read and follow label instructions.

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