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Managing weeds, and actually getting control, in corn fields takes careful planning before weeds even emerge, according to Craig Peterson, Federated agronomist at the Ogilvie location. "Putting down a good pre-emerge herbicide with multiple modes of action right after planting is the best start," he said.
Even though some of the toughest weed issues may be in soybeans -- such as waterhemp and giant ragweed (as discussed in previous issues of the Agronomy Update) -- weeds in corn are also becoming resistant to some herbicides, especially glyphosate.
"Studies have shown that weeds can start to affect yield even when the corn is only 2-4 inches [tall]," said Peterson. Products such as Acuron®, Lumax®, and Staunch® can be a great start to clean fields.
A fairly new tool, said Peterson, is the Herbicide Classification Chart, which provides information on how to get more than one mode of action when tank mixing -- the best way to combat resistance. The chart (a cut-out of which is shown above) shows, for instance, that Acuron has four active ingredients and three modes of action. Every product label includes this same information; the chart combines info from many labels.
Always consult the label of any product being considered to determine if it will cover weed pressures throughout the season. "Using a full-labeled rate of a good pre will give you the longest residual, and the best defense on resistance," said Peterson.
Even with a good pre-emerge herbicide program, today's weed battles in corn will require a post application. "Glyphosate used in the Roundup Ready crop system is the most popular," said Peterson, "but it only has one mode of action." Adding an HPPD product such as Impact®, or even adding atrazine, will boost weed control and combat resistance.
Liberty®, a Bayer product, is another good post product gaining more attention, but it also has only one mode of action, Peterson noted. Check labels for proper tank mixes and check the mode of action classification to avoid doubling up in the same categories.
"Remember," said Peterson, "post-applied products are aimed at 4-inch (or less) weeds, and timing is very important."
Your Federated Agronomist can help determine the best options to get started with clean fields and keep them clean to produce top yields and fight resistance in future crops.
In the quest for strong weed control, growers can add Halex GT to their list of solid post-emerge choices.
Halex GT offers broad-spectrum weed control and application flexibility with glyphosate and mesotrione/S-metolachlor, a combination that provides burndown and residual control of more than 90 broadleaf weeds and grasses.
Federated recommends Halex GT in the battle against herbicide resistance because it has the desired multiple modes of action (three), and has proven crop safety.
Halex GT -- "Glyphosate with Residual™" -- is a premix that provides a "convenient alternative to other post-emergence, glyphosate corn herbicide programs" (see Syngenta/Halex site).
Talk to your Federated Agronomist to see if Halex GT is the best choice for your fields this year.
Federated's annual Soybean Grower Workshops will be held in late March. Growers are invited to join these valuable discussions on key soybean topics for 2017.
Each workshop begins at 10 a.m. and concludes with lunch.
Please RSVP to your local Federated Agronomist .
- Mon., March 20 - Osceola
- Tues., March 21 - Albertville
- Wed., March 22 - Ogilvie
- Thurs., March 23 - Rush City
- Fri., March 24 - Isanti
In the last Agronomy Update, this series on herbicide-resistant weeds looked at waterhemp; now the conversation moves to giant ragweed.
"This herbicide-resistant weed is showing up in [our] area," according to Bob Marquette, Federated agronomist at the Albertville location, and "without proper management [giant ragweed] will find its way to other parts of Federated's trade area, if it already hasn't."
Giant ragweed resistance was first found with Group 2 herbicides (ALS-inhibitors) in the late 1990s in the "I" states (IL, IN, IA) and Ohio. "You probably know [Group 2] herbicides as Pursuit and Raptor," said Marquette.
"Resistance with giant ragweed is not new," he said, but "what is new is its resistance to Group 9 (glyphosate/Roundup®)." Resistance to what has become the go-to herbicide started showing up in the last few years, and is now confirmed in 11 states across the Midwest and southern U.S.
Resistance was built through repeated use of glyphosate year after year, first in soybeans and then in corn. "We found problem fields in both crops in Albertville this past growing season," said Marquette.
Giant ragweed is a "huge problem because of its competitiveness" and the fact that it produces a "massive number of seeds," Marquette noted. The battle with these weeds will intensify if growers don't take action. And the answer lies in modes of action.
As discussed in previous articles in this series, multiple, layered modes of action are being touted as the best option for achieving the desired level of weed control. And multiple, layered modes of action translates as "pre-emerge treatments followed by a solid early post-emerge program, and possibly a second post application," said Marquette.
"The new Roundup-Ready 2 Xtend® (dicamba) weed control system looks like it could be one piece of the puzzle" to get or keep control of giant ragweed, "but it needs to be used in conjunction with a good pre-emerge program to get the results we're after," he said, emphasizing that RR 2 Xtend is not a stand-alone product.
The battle rages with herbicide-resistant weeds. Talk to your Federated Agronomist to determine what products and programs should be in your weed-control arsenal.
All across Federated's service areas, a pop-up, in-row starter is recommended to get corn off to a fast and strong start, according to Tim Stelter, Federated agronomist at the Osceola location.
"We have a clear liquid that is 100% ortho," said Stelter, "and we have XLR-rate™ that is 80% ortho and 20% poly, which is a high-quality, seed-safe starter fertilizer (7-23-5) that mixes well with other micronutrients, especially zinc, the critical nutrient for corn development." (XLR-rate can also be used later in the year as foliar feeding.)
XLR-rate, a CHS product, can be combined with USA500, a Rosen's product, for complete pop-up nutrition on corn. It has four active ingredients, including zinc, that help release the phosphate tied up in the soil. USA500 also increases the availability of nitrogen, sulfur, and other important nutrients in the soil.
"These products are easy to handle, environmentally friendly, tested, and reliable," said Stelter. Whether it's applied in traditional two-by-two placement or in furrow, there's good value in start-up fertilizer.
Liquid fertilizer starters will be part of an in-depth discussion at next week's corn grower meetings (see info at right). Talk to the Federated Agronomists at the Corn Grower Workshops.
Federated recommends herbicide programs designed around the problematic weeds, and "more often than not, we are seeing waterhemp and giant ragweed together," said Kevin Carlson, Federated's senior agronomist.
Carlson said, "From a pre-emerge standpoint, we have to ask what works on both [waterhemp and giant ragweed?"
Bryan Thompson of Rosen's said, "Blanket® 4F is a liquid straight goods sulfentrazone product that's one of the best pre-emerge active ingredients on the market for waterhemp." In the fight against giant ragweed, Blanket 4F tank mixed with Sonic® or Authority® First can be an effective choice. Thompson said this "agronomically sound" tank mix offers "considerable savings to the grower" when both weed species are present.
"Blanket 4F is comparable in formulation to FMC's Spartan® 4F, and it works well as a supplement to Sonic and other popular pre-emerge herbicides," Thompson said.
A tank mix of 2 oz./ac. of Blanket 4F with 3 oz./ac. of Sonic or Authority First offers about the same amount of sulfentrazone as 5 oz./ac. of Sonic, but at a lower cost -- and this mix offers residual control of both waterhemp and giant ragweed. Thompson said, "As a rule of thumb, every 1 oz./ac. of Blanket will add approximately one week of additional residual control." Carlson added that there "is no additional benefit to go with the higher rate of Sonic for giant ragweed."
For a broader spectrum of control -- in the absence of giant ragweed -- growers can choose Blanket 4F on its own, or with a variety of other combinations, such as Blanket 4F tank mixed with Sencor, Dual, or Outlook (or their generic/private label versions). These options provide "two modes of action to control waterhemp and many other small-seeded broadleaves," said Thompson.
The photo at right, taken by last summer by Thompson in St. Peter, MN, shows soybeans (in a field with waterhemp and giant ragweed pressure) 50 days after a pre-emerge application of Sonic plus Blanket 4F at 3 oz./ac. each -- with no post treatment or burner product applied.
It's not too early to discuss tough weed control options for 2017. Contact your Federated Agronomist to design a program that fits your specific weed issues.
Federated's 2017 Corn Grower Workshops start on Mon., Feb. 20, and continue through Feb. 24. Each workshop, beginning at 10 a.m., will focus on the theme, Corn Economics and Agronomics, and will conclude with a free lunch. Contact your nearest Federated location to RSVP and for details on specific venues for each meeting.
- Economics x Agronomics
- Liquid Fertilizer Starters
- Monday, Feb. 20 -Osceola
- Tuesday, Feb. 21 -Rush City
- Wednesday, Feb. 22 - Ogilvie
- Thursday, Feb. 23 -Albertville
- Friday, Feb. 24 - Isanti
Another herbicide label has been approved for use with the Roundup Ready 2 Extend ® soybean system (dicamba tolerant soybeans).
Engenia herbicide, a BASF product, has been given a supplemental label for 2017 and 2018.
To learn more about this newly labeled product and how it can help in the battle against problematic weeds, contact your Federated Agronomist.
"Two things are happening at the same time in local corn and soybean fields in the Federated service area," said Kevin Carlson, Federated's senior agronomist, "the spread of waterhemp, and the development of herbicide-resistant biotypes. Both are very problematic for our growers."
The issue of herbicide resistance in waterhemp can be narrowed down to two main challenges.
Challenge #1: Waterhemp has spread significantly in the last several years, caused by waterhemp seeds being moved by equipment, birds, wind, and other environmental factors, all of which are very difficult to control. How can anyone keep the seeds out of a combine, or geese out of the fields?
Challenge #2: Once waterhemp is introduced into a field, controlling it becomes an issue because, according to Carlson, "most often it is already a herbicide-resistant biotype of some kind." And, if it is not, he added, "it will quickly become resistant to one in particular: glyphosate (Round Up®)."
To address these challenges and start to take control of waterhemp, growers need to think differently, first about the weed's characteristics, and secondly about the nature of the biotypes that have become resistant and how to select the right herbicides.
Waterhemp is a dioecious species, and thus cross pollination must occur to make seed (male plants + female plants = mixing of the gene pool.) Also, female plants are capable of producing large amounts of seed (photo at right shows small but prolific waterhemp seeds).
Other Midwest states have been dealing with the waterhemp issue longer than Minnesota and Wisconsin; Illinois has documented waterhemp to be resistant to six different site-of-action (see article below) classes of herbicides to date.
- ALS (e.g., Pursuit)
- Triazines (e.g., Sencor)
- PPO inhibitors (e.g., Flexstar)
- Glyphosate (e.g., Roundup)
- HPPD inhibitors (e.g., Callisto)
- Auxinic herbicides (e.g., 2,4-D)
Choosing the right herbicide, or combination of herbicides, becomes increasingly complex with one additional factor, according to Carlson: "These six different herbicide resistances that are known in waterhemp can also be stacked in the biotypes that become resistant." In other words, a grower could conceivably spray all six herbicides in a field at the same time in a tank-mix and not kill some or all of the population of waterhemp in a field.
Thus, said Carlson, "It comes down to management. Herbicide management." And it is no simple task.
Federated Agronomists are ready to help growers face the challenge of waterhemp and other herbicide resistant weeds. Call with your questions and concerns. Also watch for more information on this important topic at the Soybean Grower Workshops.
Herbicide-resistant weeds often bring conversations around to modes or sites of action. The mode of action is "the way in which a herbicide controls susceptible plants," while the site of action is "the specific biochemical site that is affected by the herbicide."* These two terms are often used interchangeably.
John Swanson, Federated agronomist at the Ogilvie location, recently attended a presentation by Kevin Bradley of the University of Missouri. Discussing modes (and/or sites) of action, Bradley tried "to help those of us in Minnesota and Wisconsin to avoid the situation . . . in Missouri," said Swanson. Herbicide resistant waterhemp and Palmer Amaranth are taking root in an extremely high percentage of their acres.
Bradly reported that Missouri growers are seeing resistance to two modes of action, and they have as high as five modes of resistance in one weed species. What can Minnesota growers learn from them? Swanson outlined several facts, based on Bradley's presentation.
- Continue -- or increase -- use of pre-emerge programs.
- There is currently no resistance to Group 15 herbicides. Weeds that don't germinate and emerge are significantly less likely to become resistant to herbicides.
- Rotate modes of action, but more importantly, mix modes of action.
- According to Bradley, using multiple modes of action in tank mixes during a single crop year has been more effective than merely rotating modes of action.
- The more modes being applied, the better the chance of killing weeds and not allowing a resistant population to survive and/or explode.
- Layer residual products.
- Missouri growers have found major success with residual products because hard-to-control weeds can germinate for long periods of time (the trait that makes them hard to control).
- It is important to lay down a pre-emerge herbicide as part of a base program, but then add a residual product with a post application "to continue to help prevent these weeds from germinating later in the season, when we can't go back and spray," said Swanson (Dual® is a good example).
"We have some very hard-to-control and resistant weeds coming our way," said Swanson, "and we need to learn from others and not make the same mistakes they did." Following these basic guidelines will set Minnesota and Wisconsin growers on the right path.
Contact your Federated Agronomist to further discuss modes of action and application programs for 2017.
*See this link for a more complete discussion of the terms, as defined by Dr. Joe Armstrong of the University of Oklahoma Cooperative Extension Service.
- Continue -- or increase -- use of pre-emerge programs.