Agronomy News > The Best Weed Control Begins Early

The Best Weed Control Begins Early

Jun 12, 2018


 

With soybeans up and growing, now is the time to watch for weed competition in your fields. Timely scouting and proper planning are critical to setting the groundwork for an effective, season-long weed management program.
 
Maintaining weed-free fields is especially critical if you have confirmed or suspected herbicide-resistant weeds in your soybean acres. According to Purdue University research, Palmer amaranth alone can create yield losses up to 79 percent in soybeans when left uncontrolled throughout the growing season. Glyphosate resistance may get the most attention, but it isn’t the only problem. Weeds have developed resistance to 23 of the 26 known herbicide sites of action, which are available in 160 herbicides, according to the International Survey of Herbicide Resistant Weeds.
 
Keep these points in mind when developing a postemergence herbicide strategy:

  1. Layer residual herbicides. Under normal conditions, preemergence herbicides typically provide about 30 days of residual control. Sequential herbicide applications can extend that length of control to help secure yield potential. Overlapping is key, so apply postemergence herbicides within 21 days after planting, with exact timing depending on row spacing and canopy closure. Keep in mind that anticipated length of residual control should be shortened in fields with confirmed or suspected herbicide resistance.

 

  1. Be proactive against weed resistance. Herbicide resistance can’t be diagnosed by visual inspection, but knowing the signs can help you determine if there might be an issue. Common signs include weed escapes from a single species, live plants found near dead plants of the same species, patchy or uneven distribution of escapes within a field, and small weeds that survive a full-rate herbicide application. If you suspect herbicide resistance in your fields, contact us to help collect and test samples. In any scenario, herbicide tank mixes that deliver multiple sites of action offer the highest level of control and lower the potential of resistance development.

 

  1. Manage weed escapes. Regardless of whether resistance is suspected or you have confirmed populations of resistant weeds, control weed escapes before they can produce seeds. This can be achieved through spot applications, mechanical control, cultivation or controlled burns. A few uncontrolled weeds here and there may have minimal yield impact this season, but seeds scattered from these weeds add to the soil seed bank and will compound the problem in the future, especially if they are herbicide-resistant.

 

  1. Scout often and take action. Timing is crucial to effective control. Make herbicide applications when weeds are less than 4 inches tall. Some weed species, such as pigweed, can grow several inches per day in warm temperatures. That gives you a short window of time to have the best chance of success.

 
Timely herbicide applications can help prevent yield loss from tough-to-control weeds this season. They can also stop seed production that will make future seasons more challenging. Based on conditions we’ve seen so far, we recommend a tank mix including FlexstarGT 3.5 at 3.5 pt/acre plus Class Act Flex at 1 gal/100 gal of water, using 15 gallons of water minimum for carrier.
 
Contact us for more information about proven weed-control solutions that can help protect yield potential through harvest.



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