It is approved and proven and may be a thing of the past

Written by Dr. Jason Weirich on .

Atrazine has been in the news lately. Given that the chemistry, ap­proved long ago, is under regulatory review yet again, I think it’s worth going over just how it works and why it is important.

Let’s start off by taking a look at the mode of action of atrazine. Atrazine is a photosynthetic inhib­itor—more specifically a Photosys­tem II inhibitor. As many as half of available herbicides have a mode of action that involves interaction with some component in the energy transfer chain of Photosystem II. In early plant science classes we learned that the transfer of elec­trons from PSII to PSI is essential for the production of photosyn­thetic energy. By interrupting the photosynthetic pathway, the plant becomes unable to fix CO2, which results in its inability to produce the nutrients the plant needs to survive. The mode of action is unique and efficient.

You may wonder why I launched this column with a chemistry lesson. I did it as an insight into the specter of weed resistance. You are well aware of weed resistance and the struggles it can bring to your operation. In previous columns, you’ve seen me write about herbi­cide modes of action and the fact that effective modes of action make for effective weed control programs. In fact, you’ve probably grown tired of me writing about it. But, resis­tance is something to think about as we wait to see if atrazine stays on the market. If we lose atrazine, we will lose one of those effective modes of action—one of the critical tools in our tool box.

If EPA pulls the registration for atrazine, there will be significant agronomic ramifications. In the short term, you can expect to see an increase in the density of broadleaf weeds—not only in cornfields but subsequent soybeans as well. You know that weed density is greatly influenced by the previous year’s production practices. There is al­ways someone in the neighborhood with a persistent weed problem, right? It’s that grower who can’t quite get ahead of a growing weed population. The weed seed bank on his place just increases every year.

Another perspective is all those prevented-planting acres from the summer of 2015. The weeds that went uncontrolled will cause trouble for several years to come. The point is, the weed seed bank in your soil is something you have to manage with the tools available on the market. We’re deep into a period with no real new chemistries headed for the market. We can’t afford to lose any herbicide tools that we have.

In fact, we haven’t had a new mode of action introduced since the 1990s, and that release was HPPD herbicides. The HPPDs con­sist of herbicides such as Callisto, Balance, Impact/Armezon, and premixes such as Lexar, Corvus, Capreno and Resicore, just to name a few. Think about your weed con­trol program. Did it include any of these? Quite a few premixes on the market today contain atrazine. For example, Halex GT, BiCep II Mag, FulTime NXT, Keystone NXT and plenty of others. If the label allows, applications of atrazine tank mixed with HPPD herbicides deliver a couple of benefits. First, when atrazine is used in combination or rotation with other products that have different modes of action, it lowers the risk of weeds developing resistance to those products. For example, weed resistance has developed in 10 ALS inhibitor herbicides used in corn. On average, 65 percent of acres treated with these herbicides also receive atrazine either in a tank mix or sequentially. The atrazine is used to slow the spread weeds resistant to the ALS class of herbicides.

Atrazine is also a useful rotational mode of action to delay the spread­ing problem of glyphosate resis­tance. For particularly hard-to-con­trol weeds like common cocklebur, Palmer amaranth, waterhemp and wild sunflower already known to be resistant to other herbicides, atra­zine is the only product which can be applied either pre- or postemer­gence that provides effective control.

Second, atrazine in combina­tion with Callisto can significantly improve weed management and has demonstrated better efficacy when these herbicides are applied postemergence for control of water­hemp, lambsquarter, giant rag­weed and Palmer amaranth. With the combination of atrazine and Callisto, there is improved control of weeds resistant to Photosystem II and ALS-inhibiting herbicides. In Missouri and other parts of the MFA trade territory, there are a lot of weeds that fit into that category. In general HPPD herbicides alone do not have exceptional levels of efficacy on many agronomically im­portant weeds without the inclusion of atrazine.

With the recent reports about HPPD-resistant waterhemp from University of Missouri Weed Scientist Dr. Kevin Bradley, it seems inevitable that HPPD resistance will increase unless atrazine is available to mitigate resistant populations. Thus, atrazine is a must-have tank mix companion to HPPD herbicides, especially because a high percentage of corn acres in Missouri receive an HPPD herbicide.

Another implication comes to mind concerning the tools we need for weed control: no-till or conservation tillage. Without the herbicides that we have today, no-till wouldn’t be an option. Weed control technology affords us the ability to use herbicides instead of cultivation for many years. And that saves soil. Keeping soil in fields is important not only from an environmental standpoint but for long term yield— and to your bottom line. When you lose topsoil, you lose nutrients and productivity. Without atrazine, no-till operations will face immense challenges, and fewer acres will enter into no-till production.

Perhaps more sobering than the agronomic challenges that would arise if atrazine is removed from the market are the bottom-line ramifications for crop production. Recent studies show that the loss of atrazine could cost an average corn grower 6.4 to 7.7 bushels per acre. If corn is $3.84 per bushel, that would cost the grower $24.50 to $29.50 per acre. I think this is a conservative estimate—and it doesn’t include the additional costs to the grower for controlling escaped weeds through additional herbicides, additional applications or tillage passes.

You’ll need more of three things if atrazine is pulled from the mar­ket: management effort, money and time. Here is why. Over the past couple of years, I have encouraged the use of overlapping residuals. This management technique is im­portant in soybeans and becoming more important in corn produc­tion. I believe that this will be the only method for effective weed control going forward. I would love to tell you that a Silver Bullet is coming down the product pipeline, but that is not the case. Atrazine is a crucial tool for managing weeds. In fact, it is often the building block for a sound management plan against weed resistance. Losing it will be costly.

Northern rootworm is an unwelcome arrival

Written by Jason Worthington on .

MFA’s Crop-Trak consultants have been finding an alarming number of northern corn rootworm (NCR) beetles in northwest Missouri and southwest Iowa. Kevin Moore with MFA’s Crop-Trak first noticed high numbers of adult northern corn rootworm in a cornfield rotated from soybean near Fairfax, Mo., in July 2016. In the weeks after that discovery, large populations of NCR beetles were discovered in multiple fields in Atchison, Nodaway, Holt, and Worth counties in Missouri as well as Page county, Iowa. The presence of a few rootworm beetles moving from corn-on-corn fields into later planted rotated cornfields is not uncommon because rootworm beetles feed on corn pollen and will seek out a food source. The alarm comes from the fact that such a high number of beetles are being found in areas where acres are dominated by corn/soybean rotations.

Rootworm species of economic importance include the northern corn rootworm first discovered in 1824 in the north central U.S. and the western corn rootworm (WCR) first discovered in western Kansas in 1868. In North America, corn rootworms are the most devastating insect pest to corn. Agronomists estimate that before the development and release of Bt corn traits to control corn rootworm larvae in 2003, 50 million acres were infested, accounting for over $1 billion in lost revenue. Before the adoption of Bt corn traits, the USDA estimated growers spent $200 million in control measures and suffered $800 million in lost yield. Yield loss and standability issues are a result of diminished root systems when rootworm larvae feeding is severe enough.

Most of Missouri’s corn is grown in a corn/soybean or corn/soybean/wheat rotation. While Missouri has populations of NCR and WCR, both species typically lay eggs in cornfields with the eggs hatching the following season. This makes corn-on-corn fields vulnerable to larvae feeding on corn roots. However, when fields are rotated to soybean, the newly hatched larvae starve without a host such as corn. Most Missouri growers have seen fewer rootworm problems than regions with more continuous corn or regions where rootworms have evolved new strains to survive.

In some areas of the Midwest, rootworm populations have adapted to crop rotation control measures. A “soybean variant” of WCR was discovered in Illinois in 1995. This strain will lay eggs in soybean in addition to corn, which makes crop rotation an ineffective method of control. Northern corn rootworm populations have also adapted to crop rotation by developing populations with an extended diapause. Extended-diapause rootworm beetles still lay eggs in cornfields, but the eggs can wait two seasons or more to hatch—allowing the larval pest to find corn roots to feed upon in a corn/soybean/corn rotation.

With high levels of northern corn rootworm beetles being documented in areas of northwest Missouri and southwest Iowa where corn on corn rotations are somewhat rare, the likelihood of extended diapause northern corn rootworm finally reaching Missouri is high. To confirm that beetles are emerging from rotated cornfields and not migrating into the fields, Crop-Trak consultants have searched for and found evidence of larval root feeding in rotated corn. Larvae and adults were also discovered by the float method in which corn roots are submerged in water causing underground larvae, pupae, or adults to float to the surface. Further confirmation of extended-diapause rootworm in Missouri is still needed. MFA’s Crop-Trak is working with the USDA, Kansas State University and the University of Minnesota for the necessary laboratory and field-testing needed to verify the cause of increased northern corn rootworm populations.

The possibility of extended-diapause northern corn rootworms in Missouri will greatly impact growers in Missouri. The two most effective methods of rootworm control, if crop rotation is not effective, is the use of Bt-rootworm hybrid traits such as SmartStax from Monsanto or Syngenta’s Duracade; or soil applied granular insecticides such as Aztec or Force. Discuss this issue with your MFA location or Crop-Trak consultant to assess rootworm threat levels and management strategies.

Pastures tend to segregate nutrients

Written by Thad Becker on .

I remember helping sort cattle when I was growing up, and it always seemed to me the nature of a cow was to do the exact opposite of what I  was trying to get it to do. I think that is why I ended up focusing on equipment and plant nutrition in my studies at college. These things might not pay attention to me either but at least I didn’t feel like I was being deliberately disobeyed.

As precision agronomy manager for MFA, I see maps from a lot of pastures that have been grid sampled through our Nutri-Track program. I think grazing animals have the same mentality as those cattle I tried to sort when they “fertilize” a field; it’s anywhere but where you want it. Of all the fields I look at, without a doubt, pastures consistently have the most variable fertility. Near shade, water, or feeding areas nutrient levels are usually high—right off the charts. Meanwhile, areas have the best potential at forage production tend to be deficient in basic soil nutrients. For this reason, I think pasture ground may have the highest opportunity for return on investment for precision nutrient application.

There are several strategies we can use to help minimize uneven redistribution of nutrients in pastures. If you are not already, I would recommend implementing a rotational grazing program that will force your livestock to move more often and better distribute manure. During the winter, rotate supplemental feeding areas as often as possible. Both of these practices will lead to a more even grazing and “fertilizing” pattern. They also move livestock to parts of the pasture they wouldn’t otherwise visit and should help reduce plant damage from heavy traffic. It is also a good idea to drag your pastures annually to break up and distribute manure.

While these practices will help mitigate the problem of uneven nutrient distribution, we have an invaluable tool in the Nutri-Track program to help us manage pasture fertility effectively. By taking samples every 2.5 acres, we can identify the distribution of nutrients and fertilize accordingly.

As is the case with other fields in the Nutri-Track program, the first thing we want to do is correct the soil pH. The pH of the soil plays a critical role in availability of nutrients and overall performance of the forage crop. This is doubly true if your pasture has legumes or you are planning to seed legumes. In fact, the MU Extension guide G4651 “Renovating Grass Sods With Legumes” states that legumes should not be seeded into fields with a pH value that is less than 6. As a bonus, it has been shown time after time that the cost of the program is paid for through the savings in lime application versus a flat-rate program.

All too often, phosphorus and potassium fertility are an overlooked component of maintaining quality pastures. Nitrogen is important and does increase grass yield, but if phosphorous and potassium are ignored too long, you will see diminishing returns from nitrogen applications. If the soil is low in these nutrients, your pasture will never reach full yield potential regardless of how much nitrogen is applied.

Balanced fertility is also an important part of stand persistence. Healthy plants are better able to with stand traffic and tough conditions, whether due to a drought or a severe winter. Maintaining a healthy stand of forage also means less room for weed pressure which may help reduce chemical costs.

In more recent times I have seen many cattleman sort and move their cattle with apparent ease. I think it’s because they know their cows and what they want, that they are able to move them so effortlessly. Similarly, we can use the Nutri-Track program to identify and understand our herd’s nutrient placement strategy and rebalance the fertility throughout our pastures. The payoff for proper soil pH and nutrient levels is a healthy pasture. They’re good to look at, but more importantly, you’ll be providing higher quality and quantities of forage for your herd.

Insect control in soybeans hinges on knowing the pest and good timing

Written by Jason Worthington on .

Pest control in soybean fields takes a more active role from growers and crop consultants than managing corn. That’s not to say scouting for corn insects is not necessary—we still have cutworms to deal with in most years. There are occasional secondary pests, and we have to be vigilant to fend off resistance to Bt traits and seed-applied insecticides. However, corn-insect management has mainly consisted of adding a pyrethroid to our pre-emerge herbicide and letting the seed treatment and the transgenic traits do the rest. At the expense of soybean yield, this attitude often carries over to soybean production. Unfortunately, if growers take this laissez-faire attitude toward pest control in soybeans, it’s likely that the soybeans will take a laissez-faire approach to yield. In the current commodity price environment, each bushel counts.

Insecticide seed treatments have become a standard operating procedure for soybean growers, and a valuable tool for early-season protection. Most commonly, these treatments are controlling below ground pests that will effect stands, along with first-generation bean leaf beetles. Bean leaf beetles not only threaten the leaves and cotyledons of soybean seedlings but can vector soybean diseases such as bean pod mottle virus. In more northern geographies where soybean aphids tend to show up earlier, seed treatments can do an excellent job of controlling early infestations. However, several caterpillar pests can still be a threat early, and later infestations of aphids and bean leaf beetles can still threaten treated soybean fields.

Late season control of insect pests in soybean production takes a much more hands-on approach. To ensure season-long control, there is no substitute for scouting. Without understanding the insect population in your field, the growth stage of the crop, and the current weather pattern, an insecticide program will not be effective.

When it comes to mid- and late-season scouting, there are a couple categories of insects to consider. The first is foliar-feeding insects and sucking insects. The second is pod-feeding insects. Foliar damage is the most noticeable plant damage and the easiest to scout for, but the least damaging. Soybean plants excel at replacing leaves if damage comes during periods of rapid vegetative growth. The most vulnerable periods are during seedling stages when insects could overwhelm small plants, and reproductive stages when vegetative growth slows. Economic thresholds at seedling and reproductive stages are around 25 percent defoliation, but can be as high 50 percent during vegetative stages.

It is important to keep these thresholds in mind when treating foliar feeding insects. A treatment for these pests can prove valuable, but may also have unintended effects. Unless you use the right product, you may increase pressure from sucking pests, specifically aphids and spider mites. Both of these pests are subject to control by beneficial insects, which are affected by insecticide treatments. The best strategy is to use products that will control both aphids and mites. Such dual control is particularly helpful in hot, dry conditions where spider mites thrive. Products like Hero which contain bifenthrin help a great deal on mites. Lorsban is a good tank mix partner with bifenthrin for mite control along with adding to aphid knockdown. Any of the neonicotinoid insecticides will provide excellent residual control of aphids.

Of course, pod-feeding insects such as podworms, stinkbugs, and even bean leaf beetles are consistently the most dangerous pests to soybeans. Little damage from these pests is needed to justify treatment, and frankly, it is rare that there is not a combination of pod-feeding insects at high enough levels to treat. Since pod feeders are present the majority of the time, applying an insecticide at pod set is a good practice.

It is still important to scout. Knowing the species of insect present is critical for good control. Caterpillars, stinkbugs, and beetles, for example, all behave differently. They are best controlled by specific products. Each pest may require different rates of insecticide for control and may or may not be affected by residual control.

To ensure proper timing and product selection, scouting for threat levels is imperative. The difficulty is scouting properly and knowing how and when to look for these pests. An extra set of eyes from a consultant in a program like MFA’s Crop-Trak can help. We’ve seen good results with Crop-Trak weekly field inspections and recommendations. Communication among this network of consultants has proven that understanding emerging threats and proactive approach to control makes an effective insect control program.

It takes more than equipment

Written by Matt Stock on .

In the past two decades, precision agriculture has seen a massive influx of technology. And the progress is still rolling. Precision is an agricultural technology that, unlike genetics or chemistry, doesn’t take a dozen years to hit the next promise.

Most advances in precision ag equipment have focused on answering one of two questions: How do I increase efficiency by reducing waste, or how do I add to the convenience of the operator? In essence, products such as automatic section control on sprayers, spreaders and planters along with automatic steering have not necessarily aided our ability to increase production outright. But, by giving us options to select the right product, at the right rate, in the right place, at the right time, they have made field operations more efficient.

But what if you want to take the next step? Variable-rate fertilizer applicators have given us the ability to implement a right-product, right-place, right-rate fertility strategy and increase productivity, but that practice is not all that new. What if we had a piece of equipment that allowed us to select the right corn hybrid or soybean variety for different parts of each field?

I recently worked on MFA’s first dual-hybrid planter. It is rolling across fields this season changing from one seed variety to another based on data cataloged for zones throughout the field.

Multi-variety planting is not an enormous challenge when it comes to equipment. Our team mounted two meters with seed-delivery hoses coming from both bulk tanks, which deliver different hybrids. The meters are electrically driven, so there is no problem with chains.

The real challenge begins with identifying where to change hybrids and why. How do you identify hybrids to best fit different areas of the field? Finally, how do you determine a plant population that is appropriate for each zone and for the hybrid that fits that zone?

To anyone in MFA’s Nutri-Track program, this concept should sound familiar; tailoring the product and amount to the need of each acre, but with seed instead of fertilizer.
Selecting the right fertilizer and rate for each acre becomes simple math for a computer when compared to past yield history and soil-test levels. But, how do you determine the right seed and population for each unique soil type and yield environment?

From the MFA precision agriculture team’s perspective, making recommendations for multi- variety planting was a challenge in selecting the right data to get the best answers.

When I started looking at the fields to be planted this year, I was lost in the data. We had more than 10 years of yield data, Veris data, elevation data, soil-test data and most importantly, firsthand experience in these fields. That may sound like a lot of information but, in my opinion, you can never have too much data.

I worked on my theories and drew different zones within these fields trying to identify what was causing yield changes in each area. But, you can look at the data all day and never get the whole story. After talking to the farmer and MFA Crop-Trak consultant, we were able to identify what drives yield in each area and get a game plan together to address problems or take advantage of each acre.

At a basic level, data can tell us where to draw a line between two field zones that differ, but experience tells us why they are different and what characteristics to look for in the variety you need for that zone. I am not a seed expert, but by interpreting the data we had collected, I was able to help our seed specialist do a better job of selecting hybrids. Our options were expanded because we didn’t need a one-size-fits-all hybrid.

Making incremental increases in yield doesn’t have to be as complicated or expensive as setting up a multi-variety planter. Maybe you just want to change the population to account for soil and fertility variability. Or, maybe you just want to make sure you aren’t limiting yield based on fertility levels. Either way, it starts with collecting the data.

The future of precision agriculture is not just equipment. It’s data. More than that, it’s interpreting data to build the insight you need to make better management decisions.


  • Subscriptions
  • Advertising
  • This email address is being protected from spambots. You need JavaScript enabled to view it.


  • This email address is being protected from spambots. You need JavaScript enabled to view it.
  • FAQ
  • Copyright Notice