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Weed Resistance Series
Battleground: Controlling Herbicide Resistant Weeds
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"A weed that never germinates, emerges, and produces seed can never develop resistance to a herbicide," said Kevin Carlson, Federated's senior agronomist, "and this is a key point to remember when we talk about the issue of weed resistance in general."
Two definitions are important to remember.
Herbicide control:
The mechanism in the plant that the herbicide detrimentally affects so that the plant succumbs to the herbicide.
Herbicide resistance:
The herbicide no longer works on the mechanism in the plant, and it lives, producing seed for the next generations.
"This is another key point: Once herbicide resistance is in a population of a weed species in a field, it never leaves. Ever. Especially the pigweeds (amaranths, such as waterhemp)," said Carlson.
The development of herbicide resistant crops, such as seen in corn and soybeans, has led to a overdependence on herbicides. It has also led to changes in agronomic practices both good and bad.
Unfortunately, bad practices have led to new problems. For example, using the same herbicide over and over in a cropping system puts pressure on the weeds to overcome the herbicide. Thus, without proper management practices and herbicide stewardship, herbicides exert high selection pressure on weeds. The end result is a shift in weed species, changes in population and density, and the development of herbicide resistance.
The challenge in today's crop and weed environment is to think differently, according to Dr. Aaron G. Hagar, a weed expert from the University of Illinois. Hagar's message, Carlson observed, was clear: Growers must think differently about amaranths (waterhemp, Palmer amaranth). Carlson added that giant ragweed should be added to that list as it appears to be glyphosate resistant in some of Federated's service area.
Without a change in thinking, more weeds will become resistant to herbicides and the cost of weed control will rise. Growers must learn to "use the management tools available today, and use them correctly," said Carlson.
The next several editions of the Agronomy Update will focus on ways to think differently about weed resistance, and why it matters. Federated's winter grower meetings will also explore this important topic. Talk to your Federated Agronomist about weed resistance -- anytime.
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Circling Back to Soil-Applied
Crop Protection Once Again
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They say history repeats itself, and weed resistance to glyphosate (in particular) is sending growers back to the "old" way of managing weeds with pre-emerge herbicides.
Two decades ago, well before Round-Up Ready® (RR) corn
or soybeans hit the
market,
pre
-emerge herbicides ruled the day. With RR seed, it became easy to kill the weeds with glyphosate
post
-emerge, and the trend moved away from soil-applied herbicides.
But today, with weed resistance issues, "there's a better chance of winning the battle," said Rod Gustafson, Federated agronomist at the Albertville location, "when we control the weeds before they even get up out of the ground."
In some cases -- as with water hemp -- pre-emerge control may be everything. "We need to keep [waterhemp] from getting out of the ground," said Gustafson, who recommended layering herbicides, starting with a control layer, a pre-emerge with residual. New weeds, such as Palmer amaranth, are moving into the area, and they also demand pre-emerge control.
In Federated's Albertville service area, according to Gustafson, many growers start weed control by impregnating dry fertilizer with a pre-emerge herbicide (such as Dual Magnum SI). "We can get a free ride on the fertilizer," said Gustafson, saving a pass through the fields and getting the ever-important multiple modes of action.
Farmers need to be proactive, not merely reactive, in the battle to control glyphosate resistant weeds. "It will become a bigger deal if farmers ignore it," said Gustafson. "It's not going away."
In the quest to beat the resistant weeds, new herbicide programs must be used with care. It is predicted that without proper management, weeds could develop resistance in as little as four years to dicamba and 2-4D (as with RR Xtend2® or Enlist E3™ soybeans, for example).
While there is resistance to post-emerge herbicides, "there is not a lot of resistance to pre-emerge chemistries, yet," said Gustafson, "so pre-emerge is a very good tool that farmers need to use."
"Be proactive, not reactive," said Gustafson. Talk to your Federated Agronomist to determine your best pre-emerge options for this coming spring.
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Acuron
® Fights Tough Weeds
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As glyphosate-resistant weeds expand (see article above), many weed control options -- especially for tough broadleaf weeds -- have become less effective. One strong option for controlling giant ragweed, waterhemp, and Palmer amaranth is Acuron®, from Syngenta®. In 2015, the National Agri-Marketing Association named Acuron as product of the year.
The problem of glyphosate resistance is pushing growers to use more pre-emerge residual herbicides at higher use rates and with more than one mode of action and active ingredient.
Acuron offers three modes of action and contains four active ingredients: bicyclopyrone, mesotrione, S-metolachlor, and atrazine. It has shown itself to provide broad-spectrum control of 70+ broadleaf weeds and grasses, including the following, in corn.
- Giant ragweed
- Common ragweed
- Palmer amaranth
- Waterhemp
- Marestail
- Cocklebur
- Morning glory
- Russian thistle
Acuron can be applied in a one-pass program at a rate of 2.5-3.0 qt./ac. (actual rate dependent on soil organic matter), from 28 days pre-plant to 12-inch corn. A two-pass option is also effective in combination with other herbicides. For those who cannot use atrazine, Acuron Flexi offers a combination of S-Metolachlor, mesotrione, and bicyclopyrone without the atrazine. This can be applied from 28 days pre-plant to 30-inch corn at a rate of 2-2.25 qt./ac.
View Acuron label.
Talk to your Federated Agronomist to discuss your particular weed control challenges and how Acuron may fit your needs.
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It's 2017: Time to Renew PSP
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Federated Co-ops, Inc., requires growers to annually update or renew their Product Service Policy (PSP) before crop protection can be purchased or applied each spring. Craig Gustafson, Federated's eastern division agronomy manager, explained the key reasons why this is required.
First, change is continuous and the demands of agri-business are increasingly complex. Federated understands these changes and is here to help you -- our growers -- navigate the challenges the changes create.
Secondly, the Product Service Policy is a communication tool. The PSP allows growers to clearly convey their plans to Federated, which in turn enables the Federated team of agronomists, applicators, and suppliers to provide their best level of performance and service.
Thirdly, understanding crop protection products and their proper use is extremely important. Knowing more about the product prior to application is the first defense against misapplication.
The product labels include valuable information, including but not limited to:
- which weeds are controlled by the product,
- application rates and timing,
- soil types and textures in which the product performs best,
- crop rotation considerations,
- groundwater and grazing restrictions,
- required setbacks, and
- re-entry intervals.
Additional crop protection product information is available online at
this link.
Go to product search and enter the brand name of the product; from the list provided, you can download or view any label, according to Gustafson.
Fortunately, the PSP has not changed this year (as compared to 2016). "However," said Gustafson, "there are new crop protection products available for 2017 with new label requirements."
Gustafson added this reminder: Always refer to the product label for all directions. "The label is the law," he said.
Members of the Federated agronomy team will be contacting growers throughout January and February to update PSP forms. Your Federated Agronomists are always ready to discuss crop protection options for your farm in 2017.
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