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Seed Armor: 12 seed treatment tips

A costume is to a comic book superhero what a baseball is to a bat. After all, who would Iron Man be without his armor?

Trouble is, one particular costume doesn’t always work for other super-heroes. Years ago, some genius fit Spider Man with a suit of armor. This protected the speedy web slinger from enemy blows. Unfortunately, the armor also stripped Spider Man of his foe-avoiding agility.

Flash forward now to the world of seed treatments. This seed armor can protect your seed against insects, disease, and nematodes. It can also enhance yields with tools like soybean inoculants.

The stakes are high these days. Before Roundup Ready soybean seed debuted in 1996, some farmers still planted no-cost bin-run seed. With costs of some highly sought-after soybean varieties now hovering around $60 per acre, spending up to $15 per acre on seed treatments makes more sense, says Shawn Conley, University of Wisconsin Extension agronomist.  

Ditto for corn. If you plant the latest multistack-traited corn with prices over $125 per acre, you need as many seeds as possible to emerge.


“You’ll read that this year’s crop is the most valuable ever,” says Conley. “From the input side, it’s the most risky ever. Seed treatments can remove some of that risk.”

Don’t forget other factors

It’s important not to let this armor immobilize other tools you use, though. With soybeans, do first things first, says Seth Naeve, University of Minnesota Extension agronomist. Start by choosing the highest-yielding, full-season varieties available.

“Then, plant these varieties with prescriptive defensive packages,” says Naeve. Seed treatments can play an agronomic role, but only if they’re used judiciously.

Some choices have already been made for you with corn, as all seed is already coated with a fungicide and insecticide. You still have a choice, though, for seed protection that fends off corn nematodes.

Here are 12 questions you may have about seed treatments and answers to help you fit them into your agronomic strategy.

1. What niche do seed treatments fit?

There’s a reason why fungicides have coated corn for decades. You plant corn earlier than soybeans in most cases, often in cool, wet soils.

“The longer the seed is in cold, wet soils, the more chance of encountering issues with fungal or insect pathogens,” says Ethan Luth, Bayer CropScience product manager.

As a result, corn hybrids have seed treated with a fungicide and an insecticide, says Luth.

Use is not as widespread in soybeans, although seed treatments are rapidly growing. Luth estimates about 70% to 75% of U.S. soybeans are now fungicide treated, with 45% to 50% treated with both insecticide and fungicide.

As with corn, you are planting soybeans earlier, too. “In 1998, just around 8% of the U.S. crop was planted by May 1,” says Conley, “In 2012, that likely was closer to 25%.”

“There is a big advantage in planting early,” says Palle Pedersen, Syngenta seed care technology manager.

A 2004 Iowa State University (ISU) study in southern Iowa found yield potential began declining as early as May 1. Yields decline an average .3 to .5 bushels per acre per day after this date, even if you plant soybeans into a good seedbed.

2. Don’t resistant soybean varieties curb disease?

They do for diseases like Phytophthora root rot. However, no varietal resistance exists for diseases like Rhizoctonia root rot and Pythium.

That’s where seed treatments come into play.

“There might be only two out of four diseases in a field that occur each year, but we don’t know which ones will occur,” says Luth. “Any one of them can be detrimental to your bottom line. That’s why you’ve realized the value of seed treatments over the last several years.”

3. Do fungicide soybean seed treatments pay?

Payback hinges on yield and soybean prices. A University of Wisconsin trial examined the performance of ApronMaxx RFC and CruiserMaxx across three yield environments:

  • Low: 40 bushels per acre
  • Medium: 60 bushels per acre
  • High: 80 bushels per acre

Payoff was also pegged across three soybean price levels:

  • $6 per bushel
  • $9 per bushel
  • $12 per bushel

At the time, ApronMaxx RFC cost $4 per acre and CruiserMaxx cost $10 per acre. In the high-yield and $12-per-acre price environments, scientists calculated a 94% and 98% chance of breaking even with ApronMaxx and CruiserMaxx, respectively. Break-even odds decreased at lower levels, though. Break-even odds at the 40-bushel-per-acre and $6-per-bushel levels were 42% and 3% for the ApronMaxx and CruiserMaxx, respectively.

Weather conditions, though, must be considered. Fungicide seed treatments work well during cool and wet springs that are coupled with late-April and early-May planting, says Conley. The ability to hold constant or to decrease seeding rate when using a fungicide seed treatment must also be considered.

4. Where do insecticide seed treatments fit?  

In corn, you don’t have a choice, says Christian Krupke, Purdue University Extension entomologist. High corn prices and convenience have combined to make them the rule in corn, even where populations of early-season insects are low.

Resistance is always a concern when a control measure is automatically applied. That’s not the case with insecticide seed treatments, though. Resistance risks are low because few insects actually encounter chemical in most fields, says Krupke.

With soybeans, response depends on location. “In Indiana, we don’t see much response because early-season insects aren’t much of a problem,” says Shaun Casteel, Purdue University Extension agronomist. “In areas like Minnesota or northern Illinois, though, soybean aphids can come in early. It’s important to understand your location.”

5. How long do they protect against pests?

Normally, 30 to 45 days, depending on disease pressure. This protects plants while they get off to a good start, says Luth. The window is similar for early-season insects, he adds.

“Ultimately, we want to protect the plant long enough to get it out of the ground and to get its root system going,” says Luth.

6. What are neonicotinoid insecticide seed treatments?

These are the ones you commonly use on corn, soybeans, and other field crops. Neonicotinoid seed treatments premiered in corn in the 1990s with Gaucho seed treatment, an imidacloprid insecticide. In the early 2000s, clothianidin (Poncho) and thiamethoxam (Cruiser) hit the market.


Most are water soluble and break down slowly in the environment. This allows plants to take them up in leaves and stems for insect protection during early plant growth stages.

7. Do any drawbacks exist with neonicotinoid insecticides?

Yes. Clothianidin, Poncho’s active ingredient, is one of the most toxic insecticides known for honeybees, say Krupke and Greg Hunt, another Purdue entomologist who analyzed the impact of neonicotinoid seed treatments on honeybees. These insecticides are toxic to a broad range of insects and soil and water invertebrates, including earthworms, adds Krupke.

A massive bee kill in Germany in 2008 occurred from exposure to clothianidin. Mitigating circumstances existed in this case, and Bayer CropScience officials say the seed treatment was not applied appropriately to the seed. This caused the clothianidin to spread from seed to the honeybees. Seeding machines also contributed to the atmospheric dustoff.

The German government suspended clothianidin for use as a corn seed treatment following the incident. (It has lifted suspensions on other seed treatments.) Currently, the European Union is considering a neonicotinoid seed treatment ban.

Pressure for a ban is not as extreme in the U.S. However, a group of environmentalists and beekeepers recently filed suit against the EPA for approving the pesticide class.

8. What can I do to protect honeybees?

The following steps from Bayer CropScience officials can enable you to reduce accidental honeybee exposure to neonicotinoid seed treatments.

  • Plant only well-conditioned seed. “Removing dust or small seed fragments prior to treatment can minimize dust potential at planting time,” says Dick Rogers, a Bayer CropScience entomologist and manager for the Bayer Bee Care Center.
  • Apply the treated seed via proper calibration.
  • Plant treated seed from a reputable manufacturer.
  • Communicate with beekeepers.

You can obtain hive locations in some states through the Drift Watch program ( This program started in Indiana in 2008 and will be in nine states for 2013. Bayer CropScience also has a bee health website at

9. Can seed treatments manage nematodes in corn and soybeans?

Yes. Syngenta includes its Avicta nematicide in its Avicta Complete Corn and Avicta Complete Beans products. Bayer CropScience pairs its Votivo nematode product with its seed insecticide Poncho in Poncho/Votivo.

Avicta actively kills nematodes as they move on the root surface. Votivo creates a barrier on roots that protects them against nematode damage through a natural soil bacterium.

Both protect roots for several weeks. “Just like soil-applied chemistries, nematodes will resurge later in the season once the protection wears off,” says Greg Tylka, ISU Extension nematologist.

ISU trials in 2011 found little benefit to these products, but nematode numbers were low.

“Their effectiveness might be different with high damaging levels of nematodes,” he says.

Soybeans tested were also varieties that resist soybean cyst nematode (SCN).

“We might see a bigger effect on yield and (reducing) nematode numbers with susceptible varieties,” Tylka says.

These products can provide inexpensive nematode insurance, particularly when they’re paired with SCN-resistant varieties on the soybean side.

“The cost on corn is just 1 to 2 bushels per acre, and it is less than 1 bushel per acre on soybeans,” he says. “There are no known adverse side effects. There could be some dividends to be reaped from these in areas with damaging populations of corn nematodes and SCN when coupled with dry weather.”

So far, no nematode-resistance issues have surfaced through such preventive treatments.

10. Do soybean inoculants work?

Odds are they will. Treating soybeans with rhizobia bacterial inoculants designed to stimulate fixation of nitrogen (N) used to have mixed success. A typical result was a Purdue University trial that compared a field of soybeans rotated with corn vs. one in which soybeans had not been grown in 15 years.


Rotated soybeans showed no response to an inoculant. Meanwhile, inoculated soybeans in the nonrotated field had a 12-bushel-per-acre edge over those planted in the nonrotated field.

Today’s inoculants, though, are better than past ones. They last longer and have higher concentrations of N-fixing bacteria. Most provide from 500,000 to over 1 million rhizobial cells per seed. Rather than being haphazardly poured over seed in planter boxes, many inoculants are now coated on the seed by treaters prior to planting.

Certain environmental conditions increase the likelihood of a response.

“High temperatures accompanied by drought are detrimental to soil organisms like native bacteria,” says Terry Culp, vice president of seed enhancement and foliar nutrition at Precision Laboratories. “Sandier and drier soils also have lower populations of native bacteria.”

Average yield increases in industry trials range from 1.5 to 4 bushels per acre. University results are lower, although new Purdue research over the last decade shows inoculants boost yields an average 1 bushel per acre. Costs range from $2.50 for a 140,000-seed-per-acre seeding rate to $6 for a high-quality product, says Culp. At current double-digit prices, yield increases cover inoculant costs.

11. How do I know my inoculant will work?

Buyer beware. Companies don’t have to tell you that the inoculants they sell you may contain lifeless rhizobial bacteria due to poor storage practices. Knowing how long the product has been stored and in what storage environment can help ease this worry.

“Look for products that have been packaged within the past year and that have been stored in cool, dry conditions before use,” says Russ Berndt, product manager with Becker Underwood.

12. Can too many seed treatments go on the seed?

Yes, but it’s more a function of application expertise than number of active ingredients on the seed. Treating seed is a science, but there’s also art involved. Excessive humidity, for example, can lead to planter sticking and dustoff of active seed-treatment ingredients.

Polymers can nix these drawbacks. Polymers coated on the seed boost seed flowability while retaining active ingredients.

“There is more consistency, there are fewer skips and doubles, and there is more uniform planting rate and depth,” says Berndt.

Polymers also benefit seed treatments containing neonicotinoid insecticides. By helping to prevent dustoff, any accidental exposure to honeybees can be minimized, says Bayer CropScience’s Rogers.

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