Waterhemp resistance to her­bicides is old news. Since arriving on the scene, this pesky weed has quickly developed some level of resistance to multiple sites of action. The subject of this article, water­hemp resistance to Group 27 or HPPD-inhibiting herbicides, is also nothing new. What is new—and concerning—is whether we are ap­proaching a tipping point that leads to widespread resistance.

HPPD stands for the plant enzyme, hydroxyphenylpyruvate dioxygenase, thus the need for a much easier acronym. To simplify a complex process, the inhibition of HPPD by this type of herbicide prevents plant growth by destroying chlorophyll and blocking photosynthesis.

HPPD-inhibitor herbicides include products such as Balance (pre-emer­gent only), Callisto/Explorer, Laudis, and Armezon/Impact. They are also part of many widely used premixes such as Acuron, Resicore and Lexar. HPPDs became popular in the late ’90s and early 2000s for their resid­ual activity as well as post-emergent activity, particularly with waterhemp.

Prior to HPPDs, dicamba was often the go-to herbicide for cleaning up waterhemp in corn, but products such as Callisto quickly took over. Crop safety, ease of use, low rate and overall efficacy won loyalty from growers and retailers alike. Glypho­sate also contributed to the transition from dicamba as Roundup Ready corn gained market share, but resis­tance issues made this a short-lived option for managing waterhemp.

The first chinks in the armor oc­curred over a decade ago. Resistance was reported in two seed corn pro­duction fields in Iowa and Illinois in 2009. Seed corn inbreds are not as competitive with weeds as hybrid corn. The problem is compounded by the open canopy that occurs after detasselling, so multiple post-emer­gent applications were used. The field in Illinois had also been planted in continuous corn, which created additional pressure.

Since that first discovery, HPPD resistance in waterhemp has been confirmed in multiple states, in­cluding Missouri. The University of Missouri reported several sites with resistant populations nearly 10 years ago. These trials looked at mesotrione and did not include atrazine in the mix. Atrazine tank mixed with mesotrione results in synergistic activity on waterhemp and is recommended on the label in certain circumstances. Mesotri­one alone can be effective on small plants, but atrazine becomes very important when taller plants also exist. The label cutoff for waterhemp is 3 inches without atrazine and 5 inches with atrazine. Unfortunately, plants much larger than 5 inches are often sprayed, and atrazine is almost always added when corn measures less than 12 inches.

When the MU data was released, most waterhemp in the country was still being controlled with HPPDs. At the time, the issue did not create major alarm like the other wide­spread resistance issues we had seen.

Fast forward to 2022. Multiple fields were reported to have wa­terhemp survive post-emergent applications of HPPD herbicides. Some of these included plants taller than 5 inches. A few mixes did not appear to have the correct adjuvant load. However, there were many fields where the weeds were small, the adjuvants were correct, and the weeds still survived.

In at least one field I observed, a second post-emergent pass using a different HPPD active ingredient failed after the first post-emergent pass of mesotrione failed. We collected seed in a number of these fields for resistance testing. At press time, the seeds have germinated un­der greenhouse conditions, and the plants are slowly growing. It will still be several weeks before we know whether the plants are resistant.

Even without those test results, growers should incorporate pre-emptive practices into corn weed-control programs. It is much easier to kill a weed in the soil when it has one growing point than when it has emerged with multiple grow­ing points. Relying on a post-emer­gent application to clean up emerged waterhemp in corn is fast becom­ing risky business, just as it is in soybeans. Using multiple effective modes of action prior to waterhemp emergence is key.

If you are forced to control emerged weeds, consider using an­other mode of action. In corn, that usually brings us back to dicam­ba. If you do use an HPPD after emergence, it’s important to scout the field to confirm the weed kill. Scouting may give you a chance to come back with another mode and still clean up missed weeds.

Last, but definitely not least, fol­low the label and include the proper adjuvants at the correct rates.

Regardless of whether last year’s issues are confirmed to be herbi­cide resistance or are attributed to weather or other conditions, we know it is now tougher to control weeds that we’ve controlled in the past. Incorporating an aggressive “start clean, stay clean” approach will help preserve one of the few weed control tools we have for waterhemp.

There are multiple factors at play in raising a tremendous crop. While many variables are beyond your con­trol, Team MFA encourages produc­ers to focus on the “Top 5” factors that you can absolutely influence:

1. Soil conditions at planting time

2. Seed placement

3. Seed quality

4. Planting the right hybrid in the right field

5. Post-planting management

As we approach spring planting, growers need to be thinking about all five of these, but today I will focus on the first two factors.

Planting into proper soil con­ditions is critical enough that you need to forget what the calendar says and keep a sharp eye on soil temperature and moisture. Corn, for example, requires a soil temperature of 50 degrees to germinate. A corn seed also takes in its first moisture needed to germinate within 24 to 48 hours after planting. If this moisture is cold, it can cause cell damage, which results in what is known as imbibitional chilling. The damaged tissue from imbibitional chilling can lead to poor and uneven emergence. It also opens the door for seedling diseases to attack. For these reasons, in addition to watching current soil temperatures, you need to watch the forecast for the 48 hours after the anticipated planting date.

For optimal emergence, it is important to wait for excessive soil moisture to dissipate. Planting into wet soils will cause disk openers to smear the sides of the seed trench to the point that the closing wheels cannot properly fracture them. This is known as sidewall compac­tion, which leads to improper root development. In this situation, the roots proliferate within the area opened by the disk openers but not the surrounding soil, resulting in hatchet-shaped roots. This reduces nutrient uptake, anchoring ability and overall root mass.

Proper seed placement is essen­tial. A corn stand will have higher yield potential if all its plants emerge within 12 to 24 hours. To attain such uniform emergence, you need consistent seed depth.

Generally, I recommend planting corn at a minimum of 2 inches to avoid temperature fluctuations and to promote good root development. In dry soil conditions, you may need to go deeper to get all seeds into moisture. Ensuring even spacing between seeds and minimizing skips and doubles also help protect yield potential.

For all these things to happen, you must first examine the planter to make sure all parts are properly adjusted and replaced if needed. I like to start by ensuring the planter is level when down. A bubble level is usually adequate to ensure that the 7x7 bar is even with the ground. You also need to check for excessive movements in the parallel arms. If this is an issue, look for worn bush­ings that need to be replaced. Nuts and bolts should also be checked throughout the planter for proper tightness. Then, make sure the drive system is running smoothly. In the case of a mechanically driven planter, all chains need to be checked for kinks or rust, properly lubricated and replaced if needed.

From there, I find it helpful to visualize the path that the seed is taking through the planter and think about all stages in that journey. The seed first goes through the meter. Meters should be checked and calibrated on a test stand to ensure proper seed singulation. Many MFA locations and equipment dealerships have a test stand and can calibrate planter meters.

The seed then travels down the seed tube, which should be checked for wear along with the seed tube protector. Worn parts should be re­placed. A worn protector will allow contact with the disk openers, which leads to increased tube wear.

The seed then falls into the seed trench, which was cut open by the disk openers to the depth allowed by the gauge wheels. Down pressure should be set high enough to reach this desired depth, but excessive down pressure can lead to compac­tion. Maximum allowed disk opener wear should be ½ inch of new. For example, if a new opener is 15 inch­es, it should be replaced when worn under 14.5 inches.

The seed is then pressed to the bottom of the trench by a proper­ly set firmer for best seed-to-soil contact. From there, an accurately adjusted closing wheel system will fracture the sidewall of the trench and cover the seed.

Many planters are also equipped with row cleaners, which, when cor­rectly set, will move surface residue without disturbing the soil. Since all planters are different, I encourage consulting the owner’s manual for more specific recommendations.

Finally, slow down, and enjoy the ride. Planting too fast can counteract some of the positive adjustments that you have made to your planter.

The preparations you make now will factor into your success this growing season. If you need assis­tance with planter setup and evalua­tion, talk with the agronomy experts at your local MFA or AGChoice center. We’ll be happy to help.

With near-record highs of nitrogen (N), phosphorus (P) and potassium (K) as I write this article, a question I’ve been asked a lot lately is, “How much fertilizer should I ap­ply?” In response I say, “It depends.” I know. Brilliant, right?

But honestly, effective fertilization does depend on multiple factors, many of which you can control. Questions I might ask in return include, “What are your current soil test levels? What are your yield goals for this field? What are you doing to protect your fertility investment?”

As a district precision manager for MFA as well as a licensed MFA crop insurance agent, I spend much of my time thinking about risk management. Often on my mind are ways I can help farmers manage risk when it comes to fertility, and how I can help leverage their crop insur­ance to manage on-farm risk.

When it comes to managing your fertility investment, a key consid­eration is making sure that you are putting N, P and K in the right place at the right rates for the production goals of your fields. However, the first thing you need to address is soil pH. At MFA, we do that through Nutri-Track, a high-yield system that focuses on managing fertility on an acre-by-acre basis. A colleague of mine once said, “manage small for big returns,” and that hits the nail on the head.

Managing small by using Nutri- Track to properly correct pH can produce big returns. Low and high pH levels can tie up recently applied phosphorus to the point of making it unable to do its job of feeding the crop. Through precision applications, you can correct low areas with lime without raising pH in areas of fields that are already elevated or close to optimum. A flat rate of lime does not take into account current pH levels in your fields.

Much of the pH correction is done in the fall, and maybe you’ve already got your P and K applied and possibly part of your nitrogen for the upcoming crop. There are still things you can do to help pro­tect your fertility investment. One way is through in-season nitrogen management. MFA encourages split applications of nitrogen for several reasons. First, it promotes environ­mental stewardship. Second, we can better partner with our growers and provide more return on investment through accurate, in-season nitrogen recommendations.

MFA uses the Nutri-Track N com­puter model, powered by Adapt-N, to account for in-season losses through weather events and growing conditions on your specific fields. This allows our precision agronomy specialists to make an accurate ni­trogen recommendation during the growing season, which can go a long way toward helping maximize inputs applied ahead of your crop.

What if you haven’t yet applied P and K for next season? Nutri-Track is highly customizable. MFA fertility recommendations feature a build and removal component, and these types of recommendations provide the best results in my experience. However, in years with higher P and K prices, on some fields it may make sense to focus on removal only. May­be rented ground fits this scenario for your operation.

MFA can use yield monitor data to create recommendations that replen­ish P and K removed by the previous crop. While this option doesn’t build soil fertility, it can help place fertility where it will do the most good in the short term. The needed nutrients go to more productive acres without over-applying on less-productive acres. Better fertility placement allows you to raise overall farm yield averages and return on investment. Applying more P or K where you don’t need it—and not enough where you could use more—doesn’t make much sense. The removal-only approach, using yield monitor data, allows us to remedy that.

If you are not enrolled in Nutri- Track or don’t have a yield monitor for more precise recommendations, let me caution you that cutting fertilizer application rates on all fields equally is not the way to go. Focus on productivity levels and goals of each farm or field. Contact your local MFA manager, precision agronomy specialist or key account manager and work through where you should place fertility to best protect your input investment.

We must seek alternative solutions when proven products can no longer be used

When there’s an equipment breakdown, farmers typically reach for their tool set to get their machine up and running again. A few weeks ago, my 4-year-old daughter wanted to ride her battery-powered John Deere Gator Power Wheels. I unplugged the power cord from the wall receptacle and clipped the battery terminals together. Before we could head down the driveway, though, I needed to insert the screw that held the front bumper and battery in place. I generally leave my red-handled #2 Phillips screwdriver next to the toy, but this time it was missing and couldn’t be found.

The bottom line was that I didn’t have the necessary tool to complete the task and move forward. I had two options: find a different tool (a pocketknife) that could be used to achieve a similar outcome or leave the toy in the garage. Any parents reading this will understand that leaving the toy in the garage was not an option that day.

When it comes to crop protection tools—fungicides, herbicides and insecticides—we often have options to manage a given pest. Today’s tools are vastly more advanced than earlier civilizations that used sulfur products to control insects and mites. Salt was commonly used by Roman soldiers to prevent their enemies from growing crops and feeding their population. Pesticidal options over the last century have evolved from industry byproducts to active ingredients that require lower use rates, have less environmental impact, and are more specific to damaging pests.

Researchers continue to discover crop protection products, with the spotlight in recent years on fungicides. This product category has experienced more growth in active ingredient discovery than herbicides and insecticides. On the contrary, our industry continues to be squeezed on older but effective active ingredients that control some of our most troublesome pests.

One such example is chlorpyrifos, an insecticide that had several trade names such as Govern, Hatchet or Lorsban. In early 2022, the EPA revoked the use of chlorpyrifos on all food, feed and forage crops. For many producers, it was the go-to product for managing insects in corn, soybeans and alfalfa. Alfalfa has fewer labeled insecticide options when compared to crops such as corn and soybean with larger market opportunities.

Managing alfalfa aphids and alfalfa weevils will be challenging going forward due to fewer effective alternative insecticides. Additional petitions to remove other organophosphate pesticides, including acephate and malathion, have been proposed.
Atrazine is another herbicide that has been in the spotlight recently. It’s not only crucial for weed control in corn and grain sorghum but also for making other herbicide products, like Explorer, work more effectively.

A more intensive, integrated approach may be necessary in the short-term to manage certain pests that were perhaps easier to control with formerly available chemistries. In the case of my daughter’s Gator, a pocketknife was required to get me by until I could locate the lost tool or purchase a new #2 Phillips screwdriver. The time it took me to find an alternative solution was much shorter than the time it takes to get new tools registered and approved to manage weeds, diseases and insects. It takes years to get a product from lab to farm while also going through the federal and state registration processes.

I believe our industry and patrons will continue to evolve and adapt as crop protection tools come and go. The exciting part to me is there are many creative, intelligent minds working in product discovery with the passion to provide solutions.

Team MFA is no different. The wealth of knowledge and experience of our team members is immense and provides a contemporary approach to providing whole-farm solutions to our customers, just as we have for more than 100 years.

Doug Spaunhorst
MFA Director of agronomy
This email address is being protected from spambots. You need JavaScript enabled to view it.

Read more in this Dec/Jan2023 issue of Today’s Farmer