Do seed treatments pay off?

Central Indiana farmers soaked up warm temperatures and sunshine as they worked fields in mid-April 2021.

“There was a lot of planting going on at that time, including soybeans,” says Christian Krupke, a Purdue University entomologist. Farmers have trended toward early soybean planting when weather permits to capture more yield potential, he adds.

Still, it wasn’t blue sky and eatin’ peanuts, as cool and wet conditions reigned following planting. Frost and snow in some fields yielded freezing water that ruptured plant cells and spurred necrosis. This left soybeans prone to damage by seed corn maggot larvae, he says.

“When cool and wet soils overlap with germinating soybeans, there’s no way to keep seed corn maggots away,” says Krupke. Left unchecked, this subterranean pest decimates corn and soybean stands.

Enter insecticidal seed treatments (ISTs). Farmers team these with fungicide seed treatments to help ensure stand establishment and early-season growth by nixing early-season insects such as seed corn maggots.

They weren’t a silver bullet in 2021 for central Indiana farmers, though.

“We received a lot of calls about stand reductions [from seed corn maggots],” he says. “Little difference existed between IST seed and untreated seed.”

In other cases, ISTs have delivered as promised. “We have data over numerous years for an economic benefit from insecticide treatments in both corn and soybeans,” says Sebe Brown, University of Tennessee Extension entomologist. Read more about the data here.

Early-Season Stressors

“Corn is extremely sensitive to stand loss,” says Nick Tinsley, BASF technical field representative — seed treatment.

“The occurrence of diseases that affect seed corn are difficult, if not impossible, to predict prior to the growing season. If they occur, there’s nothing that a grower can do to alleviate disease.”

Stand loss isn’t quite as crucial with soybeans, as they can fill in areas depleted by disease-triggered uniform stand loss, he says. Still, the trend toward lower seeding rates to slice seed costs and toward early planting is erasing this advantage.

Early-planted soybeans tend to encounter cooler and harsher weather, which slows germination and stand establishment, says Dale Ireland, Syngenta technical product lead for U.S. soybean & corn seed care. This increases the odds of disease pathogens overwhelming seeds and seedlings, he adds.

Early-season insects also can decimate corn and soybeans. Unlike with disease, branching out doesn’t spare soybeans from injury by insects. Damage patterns are patchy, which makes it more difficult for soybeans to fill in, says Tinsley.

Meanwhile, insect infestations are unpredictable between years, says Tinsley. Scouting for below-the-soil insects is akin to trying to hand-catch a trout swimming through a fast-flowing stream.

“The other aspect is that if you do scout, what will you do with the information?” Tinsley asks. “A lot of thresholds for these [subterranean] insects were developed in the 1980s. They haven’t been updated to reflect current cost of production or commodity prices.”

In the case of corn, Krupke says insect thresholds do not reflect modern hybrids that grow faster, germinate more reliably, and have more vigor compared with older hybrids.

What's on my seed?

For the most part, farmers know nitrogen rates they apply to their corn. Ditto for the rate of herbicides they apply to crops.

Seed treatments? Well, multiple components can create a mix of seed treatment chemistries unknown to the farmer.

“Farmers don’t really know what they’re planting,” says Shawn Conley, University of Wisconsin Extension agronomist.

Pennsylvania State University and USDA scientists examined the Agricultural Resource Management Survey (ARMS) for corn in 2016 and for soybeans in 2018. (ARMS is USDA’s primary source for U.S. farm production practices.) They found that about 98% of farmers could name field-applied pesticides used on their cotton, corn, wheat, or soybean crops. Meanwhile, just 65% of corn growers and 62% of soybean growers could provide the name of the seed treatment product on their crops.

Not knowing which treatment accompanies seed and what it controls can spur failed pest control, says Conley.

“You also have to understand the rates on both diseases and insects, because rates dictate different activity on different pathogens,” he adds.

Seed Treatment Benefits

Fungicide seed treatments and ISTs that farmers use to manage these maladies have grown over the years. A Pennsylvania State University and USDA analysis of data generated by Kynetec, a third-party global marketing and research firm, found that from 2012 to 2014, 90% of corn acres and 76% of soybean acres were grown with treated seeds. Of those insecticide-treated seeds, neonicotinoids accounted for about 80%. These include:

Imidacloprid (Gaucho, Bayer)
Clothianidin (Poncho, BASF
Thiamethoxam (Cruiser, Syngenta)

Neonicotinoid ISTs can work well because they’re highly water soluble. They easily move with water inside the plant to deter insects, says Brown. Neonicotinoid ISTs also can be teamed with ISTs from other chemical classes, such as Corteva Agriscience’s Group 28 insecticide seed treatments, Lumiderm and Lumivia.

Neonicotinoid IST use is more common in corn than soybeans. However, industry studies typically find that a fungicide/neonicotinoid IST combo also has merits in soybeans by spiking yields an average 2 bushels per acre. University entomologists in the MidSouth and South have also observed a similar average yield spike.

Weather conditions that fuel disease and insect infestations make seed treatments a vital tool for farmers in the mid-South and South, says Brown. Wintertime temperatures often don’t drop enough to kill disease pathogens. This also applies to insects, he says.

“As we green up, we typically have a larger number of insects surface,” says Brown. “This coincides with the time when crops are being planted, so we can have severe issues with insects feeding on our cash crops.”

Generally, a soybean fungicide/ insecticide treatment will cost $10 to $12 per 140,000-seed unit, says Katie Jaeger, Syngenta seedcare product lead. (Soybean seeding rates vary but can range between 80,000 and 140,000 seeds per acre.)

Because 70% of the treated cost is due to the insecticide, Jaeger estimates a $20 to $21 per acre return just from the insecticide component. This assumes soybeans at a $16 per bushel price and the seed treatment insecticide portion expense of $7 to $7.50 per unit.

Midwest Findings

The payoff for neonicotinoid ISTs is not as clearcut in the Midwest. A compilation of studies in a 2019 paper representing agronomists and entomologists from 14 land-grant universities found an average soybean yield benefit of 2 bushels per acre (bpa) occurred from teaming a neonicotinoid IST with a fungicide seed treatment. At best, a yield bump of 3.3 bpa occurred. In some cases, the benefit was nearly nil, bottoming out with a slim 0.2 bpa. Read more about how neonicotinoid seed treatments of soybeans provide negligible benefits to U.S. farmers.

However, a partial economic analysis showed inconsistent evidence of a break-even cost of a fungicide-only or a fungicide/insecticidal seed treatment. Thus, widespread prophylactic use is not recommended on soybeans, according to these university entomologists and agronomists. Krupke says a 2014 Environmental Protection Agency (EPA) report backs these findings.

“We were treating 100% of our soybeans with an [neonicotinoid] insecticide,” says Jonell Myers, Beck’s seed enhancements lead. However, the Midwest agronomist/entomologist report helped prompt Beck’s to switch to Nemasect, a biological treatment that helps manage nematodes and soil-dwelling insects such as wireworms and white grubs, she says.

Insect control neonicotinoid ISTs cannot be relied upon in sopping wet and cold soils, Krupke says.

“You want the plant to be thirsty and growing, imbibing water along with that insecticide,” he says. “That doesn’t happen in cold and wet soils. Instead, the water-soluble [insecticide] compound leaches out into soil water. You could argue that the time when you most need seed treatments in cold and wet soils is when you are least likely to get those concentrations into the plant. Nothing is happening. The plant just sits there — cold and wet and stressed.

“A [neonicotinoid] seed treatment protects a vigorous growing seedling from occasional insect pests for a short time,” he adds. To work, high insecticide concentrations in the plant need to sync with insect pressure. If those factors do not line up, insect damage will occur, Krupke says.

A farmer's take

Andy Linder listened as a fellow Minnesota farmer told those attending the National No-Tillage Conference several years ago how he nixed corn and soybean seed treatment use.

Linder, who farms near Easton, Minnesota, had been wanting to reduce chemical inputs in his goal to build soil biology. He conducted on-farm trials comparing fungicide and insecticide-treated seed vs. non-treated seed.

“I was not seeing great results from planting the treated soybean seed,” he says. At best, the $15 per acre investment was a break-even proposition. He then successfully adopted planting untreated soybean seed across his farm.

Planting seed corn free of insecticide and fungicide seed treatments hasn’t been as successful, though.

“One year, the untreated corn yielded the same as the treated corn,” he says. “The next year, I actually had to replant it [due to insect damage].”

Thus, he’s retained insecticide- and fungicide-treated seed corn across his farm.

Linder says what’s worked on his farm may not work on others. Still, he says farmers don’t need to automatically use seed treatments on every acre. “We need to be responsible,” he says. “Treat only if you need to do it.”

Off-target concerns

Foliar pesticides aren’t the only chemicals where off-target potential exists. Off-target concerns also exist regarding neonicotinoid insecticide seed treatments (ISTs).

Purdue University trials show just 2% to 3% of clothianidin (Poncho, BASF) and thiamethoxam (Cruiser, Syngenta) insecticide in seed treatments ends up in the plants. Contrast this with a minimum of 2% to 3% that typically leaves the seed as dust-off during planting, says Christian Krupke, Purdue University entomologist.

This leaves around 95% of the insecticide that does not make it into the plant, says Jonathan Lundgren, director of the Ecdysis Foundation and CEO of Blue Dasher Farm, Estelline, South Dakota.

“It’s washing away and getting into plots at the margins of conservation strips and natural set-aside areas,” he says.

Without the presence of these plants [in conservation strips and set-aside areas], neonicotinoid ISTs can wash into water bodies and impact mammals and aquatic life, he adds.

“In Minnesota we commonly detect neonicotinoids [insecticides] in surface water,” says Joshua Stamper, director of the Minnesota Department of Agriculture pesticide and fertilizer management division. This normally occurs in the spring, which corresponds with planting treated neonicotinoid IST seed, he adds.

“Water-soluble chemistry like neonics are really powerful tools for growers,” Stamper says, “but when 60% to 80% of the acres in a watershed get treated seed, we should not be surprised when it’s found above levels that impact aquatic invertebrates in surface water.”

Use Rates

Neonicotinoid IST manufacturers say neonicotinoid IST use rates are much lower than used in other insecticide applications.

“We’re talking about just a half an ounce of active ingredient spread out across an acre, compared to pounds per acre of other soil-applied insecticides,” says Chip Graham, Bayer technical development specialist.

Krupke counters compound weight is irrelevant. “It is the toxicity that is important, and these compounds are far more toxic than previous insecticides,” he says. “We are actually using a lot more insecticide than ever before.” Read the analysis here.

“When you look at what’s happening in tile lines [that can transport chemicals to water bodies] with finding neonicotinoids, it tells us they are not staying where we want them to be,” says Shawn Conley, a University of Wisconsin Extension agronomist. He recommends farmers use neonicotinoid ISTs on a selective basis rather than across all their corn and soybean acres.

Mammal impact

Neonicotinoid insecticide runoff may also unfavorably impact mammals. A study reported in 2019 in Scientific Reports detailed the impacts that imidacloprid (Gaucho, Bayer) concentrations had upon white-tailed deer. As imidacloprid increased in the animal’s spleen, factors such as fawn survival, jawbone lengths, body weight, and organ weights decreased.

Subsequent examinations made by the Ecdysis Foundation show at least 60% of hunter-killed whitetailed deer show presence of imidacloprid. Such concentrations can lead to increased mortality rates and other negative impacts, says Lundgren.

Bayer scientists disagree with the findings of the 2019 Scientific Reports report. Among other factors, they say the authors reference groundwater concentrations to justify the low- and mid- neonicotinoid IST test levels. However, deer drink from surface water in which sunlight quickly breaks down imidacloprid, say Bayer scientists.

Three studies cited by the American Seed Trade Association (ASTA) also show minimal impacts from the neonicotinoid insecticide thiamethoxam upon freshwater organisms.

ASTA officials also cite work by the Vermont Agency of Agriculture, Food and Markets and the Vermont Agency of Natural Resources since 2017 on the prevalence of neonicotinoids in the environment. The work revealed no detection of neonicotinoid insecticides in Vermont hives and minimal detection in state waterways, none of which exceeded minimum thresholds set by the Environmental Protection Agency, according to ASTA officials.

Seed Separation

Three studies cited by the American Seed Trade Association (ASTA) also show minimal impacts from the neonicotinoid insecticide thiamethoxam upon freshwater organisms.

Bayer studies find that part of neonicotinoid ISTs do separate from the seed once planted. However, that’s key to efficacy for these products, says Christian Maus, Bayer entomology and pollination science lead.

“When seed is planted, insecticide sheds off the seed into the surrounding root zone,” he says. “From there, the roots of the plant take in the insecticide into the plant. With no concentration in the soil, the roots could not get the substance into the plant.”

Any leftover insecticide binds to the soil and is degraded over time, according to Maus. Bayer studies show no issues with leaching into water bodies from the ecological risk assessments it conducts.

Read more about how pesticide seed coatings are widespread but underreported.

What to Do?

“It’s really up to the individual to understand whether or not they [seed treatments] are worthwhile to use,” says Tinsley. “It’s best to think of these as defensive tools that enable farmers to protect against yield loss.”

Farmers may luck out if warm and dry weather helps diminish disease pressure. Decimated stands loom, though, if seedlings struggle against disease pathogens spurred by cool and wet weather.

“Farmers have no idea what type of year they will face,” says Ireland. Fungicide-treated corn and soybean seed can help protect against early season diseases before they impact stands, he adds.

The same prescriptive approach applies to ISTs says Chip Graham, Bayer technical development specialist.

“A lot of times we see benefits, especially with the [higher] commodity prices we now have,” Graham says.

“It’s a good insurance policy to treat seed to get maximum yield potential.”

An insect field history, no-till, and high-residue situations can heighten the odds of an IST payoff, he adds.

Fungicide soybean seed treatments have their place in the Midwest, says Shawn Conley, a University of Wisconsin Extension agronomist.

“Obviously, if you are planting early and you have a history of sudden death syndrome or Phytophthora, there is a place for effective fungicide seed treatments,” he says.

It’s more fuzzy for neonicotinoid insecticide-treated seed, though.

“I understand the [insect] challenges they have in the South and Mid-South,” he says. “In the Midwest, though, the same degree of insect pressure doesn’t exist. Bean leaf beetle is hit or miss, and soybean aphids have pretty much been absent in recent years.”

Over time, the insecticide in these products breaks down. If farmers plant soybeans early, this decreased residual may not be sufficient to control later emerging insects, says Conley.

“We just don’t have to have a neonicotinoid (IST) on every soybean acre,” Conley adds. “I would never say never, but I just think more judicious thought on acre placement must be put into use of these products.”