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Here is your latest issue of AgFax Weed Solutions, sponsored by Nufarm's Midwestern and Southern field teams.
 
Editor: Owen Taylor
Web Editor: Ernst Undesser

IN THIS ISSUE

Editor’s Picks: 7 posts covering resistance management, new developments and regulatory shifts.

Midwestern Focus: 9 items from Illinois, Indiana, Iowa, Minnesota and Nebraska.

Southern Focus: 6 items from Arkansas, Georgia, North Carolina, Tennessee and Texas.

Worth Noting: “A Bad Way To Start The Year” -- in our scan of social media and weed-related topics, this tweet from Iowa State’s Bob Hartzler really stood out. That’s Palmer pigweed, we assume.

EDITOR'S PICKS
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Combines can hide thousands if not millions of weed seed even after a conventional cleaning, a team of researchers finds. As they also show, adding a bit of “roughage” to the machine’s diet can flush out weed seeds hiding in the system and greatly reduce the chance of spreading resistant populations across a wider area.

   
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University of Missouri researchers are about to start their fifth year of studying the practical physics of those inversions that can move dicamba way off target. Some of their findings might line up with your perceptions but others – based on intense tracking – my offer significant surprises and insights.
   
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Knowledge of adjuvant activation helps with proper adjuvant selection. There are three primary adjuvant categories: surfactants, oil-based adjuvants and spray utility agents. All have a purpose that may or may not fit with what you need when the nozzle starts riding over the field.
   
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The objective is to spread a maximum dose of herbicide on weeds, which would mean less herbicide would be used and zero drift could be expected. The concept will be waiting for the right robotic setup to make it work.
   
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EPA will require that anyone who purchases, mixes or applies a paraquat-containing herbicides must complete an online safety training module ahead of the 2020 season. The training module is now available and can be taken anytime.  As a bonus, the training will be good for three years. 
   
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State regulators are expressing alarm at this development, particularly those dealing with widespread dicamba injury, which appears to be the catalyst for EPA’s announcement.
   
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EPA released a notice on March 18 that the agency had received Bayer’s application to add new corn uses to the label of its dicamba herbicide XtendiMax, to prepare for dicamba-tolerant corn hybrids.
   
MIDWESTERN FOCUS
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The introduction of Palmer amaranth has the potential to significantly impact Iowa crop production in the future.  But as the saying goes, there’s a silver lining behind every cloud, and Palmer amaranth’s silver lining might just be the Iowa Noxious Weed Law. 
   
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Increased use of ammonium thiosulfate (ATS) is being driven by the fact that sulfur deficiency symptoms are showing up on fields with low sulfur soil test levels. Plenty of people are asking whether ATS has an affect on weed control with glyphosate and glyphosate plus 2,4-D. Here’s a close look at the finer points.
   
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Spring weather has finally arrived and fieldwork will begin soon. Here's how to approach cover crop termination, based on research by Iowa State University.
   
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 Extension Weed Specialist Amit Jhala delves into which weed species need to be controlled now with spring burndown applications. He also addresses burndown challenges and how to overcome them, as well as herbicide modes of action used for burndowns.
   
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Because of the importance of cover crop biomass as a weed-management tool, it is essential to manage fields to maximize growth. Here are a couple of key questions and answers to consider ahead of next season if you see cover crops as an option.
   
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Waterhemp has evolved resistance to herbicides from more site-of-action groups than any other Illinois weed species. It’s like a who's who list of chemistries and modes of action. “Perhaps even more daunting is the occurrence of multiple herbicide resistances within individual plants and/or fields.”
   
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"Consider the likelihood of resistant horseweed biotypes in the field. HG 9 (glyphosate) and HG 2 (ALS) resistant populations are widespread across the state."
   
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While these plants may not be glyphosate resistant, ranchers are concerned they are losing valuable grazing due to this plant.
   
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In 2018, Palmer was reported at 44 sites across 6 Minnesota counties. That number will likely go up in 2019. Minnesota Department of Agriculture’s Noxious Weed and Hemp Unit Supervisor Tony Cortilet discusses Minnesota’s response to date and what can be done at the field level to stop or at least slow it’s spread.
   
SOUTHERN FOCUS
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Avat Shekoofa, University of Tennessee agronomist, discusses research on Palmer pigweed and the effect that different cover crop species and termination timings have on the weed's ability to germinate.
   
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With the recent global approval of the LibertyLink GT27 and Enlist E3 soybean traits, there seems to be some confusion or uncertainty as to what glyphosate products can be applied to these crops.
   
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Like all weeds, volunteer corn uses water and nutrients in addition to shading young cotton plants all of which causes a yield loss. Additionally, heavy volunteer corn can cause cotton harvest challenges. Here are options for either preventing or eliminating this competitor.
   
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Rainy conditions have delayed burndown applications ahead of corn, which is a critical situation where resistant grasses have gained ground. For most weeds, though, late burndown in corn can be very effective and safe. After all, atrazine is a great burndown addition to paraquat.
   
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Two of the most common winter weeds in this scenario are wild radish and cutleaf evening primrose. They are typically harder to control in reduced-till.
   
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Burndown strategies have to be taken into account when cold steel is needed to clean up ruts and other damage from last year’s wet harvest. Include a residual in your approach since tillage can stimulate long-buried weed seeds from seasons past.
   
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This difference between clethodim herbicides can and does cause confusion.  It can also make it difficult for the average applicator to price shop as often the price quoted is not comparing the same percent active ingredient or surfactant package.
   
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In peanuts, yield losses due to weeds are minimized when fields are free of weed competition for the first 4 to 6 weeks after planting. The use of preplant, preplant incorporation and preemerge herbicides are critical for minimizing weed competition during the early season. Plus, you set the stage for cleaner fields as the season progresses.
 
WORTH NOTING:
A Bad Way To Start The Year
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