In the same year USGS gave up on tracking insecticides used via seed treatments, EPA set off a firestorm in the industry by releasing an economic benefits analysis concluding that seed treatments on soybeans offered no real economic benefit to farmers, with the exception of the southern U.S. where pest populations are more intense. Over the next few years, many academic entomologists in the Midwest and Southeast have come to agree with those conclusions. Most recently, some entomologists are starting to question the value of widespread, prophylactic seed treatment use in Midwestern corn fields as well. See more here: https://www.epa.gov/… and here: https://besjournals.onlinelibrary.wiley.com/….
Seed and agrichemical companies have strongly objected to these conclusions and, in 2015, they commissioned their own study from a group called AgInformatics, which analyzed published studies, industry field trials and insecticide screening tests and asked farmers to self-report the monetary value of seed treatments to them. The studies concluded they were very valuable, on all crops. See it here: http://aginfomatics.com/….
Academic scientists' conclusions are based more on independent field studies and the biology of the soil-dwelling pests targeted by seed insecticides, such as seedcorn maggot, wireworms, grubs and bean leaf beetle. All can be very damaging insects, but they tend to be sporadic pests in much of the corn and soybean-growing parts of the country, noted Christian Krupke, a Purdue University entomologist who has led many studies scrutinizing neonicotinoid benefits. Other insects targeted by seed treatments, such as soybean aphid, typically reach economically damaging levels later in the summer, beyond the timeframe that neonicotinoids are present in crop tissue in significant concentrations. The result is farmers treating more corn and soybean acres with insecticides than ever before, as insurance against sporadic pests whose populations have not increased in the same timeframe, Krupke and fellow Penn State entomologist John Tooker concluded in a recent report. See more here: https://www.frontiersin.org/….
It took a lot of data to sway some scientists to this conclusion. University of Wisconsin soybean agronomist Shawn Conley recommended seed treatments for many years, especially for farmers trying to push soybean planting earlier each year.
"I'm the poster boy of someone who has 'flip-flopped' on this," Conley noted. "Of course, what really happened is that the data generation increased. We started off with a few data points, just in Wisconsin. But when I started looking at it from a national perspective, it changed." Two years ago, Conley and a team of 22 entomologists, plant pathologists and statisticians released a meta-study of 194 field studies across 14 states concluding that no part of the soybean seed treatment package -- insecticide or fungicide -- paid off for farmers in the Midwest, mid-Atlantic or Southeast states comprising 85% of U.S. soybean acreage.
"We found that, yes, there are certain situations, such as high manure or in cover crop systems, where the higher risk of insects means the insecticide has a chance of actually controlling an insect," Conley explained. "But overall, for the broad prophylactic treatment of every acre, the return on investment was basically zero. If anyone makes money, it's not the farmer. At most they might break even." (See more on that study here: https://www.dtnpf.com/… and here: https://www.nature.com/…)
The notable exception to these conclusions has been the Midsouth region, where mild winters and long growing seasons lead to considerably more pest pressure, explained Mississippi State University entomologist Angus Catchot. For cotton growers, neonicotinoid seed treatments are a staple in the fight against thrips, a pest whose annual likelihood is "pretty much 100%" as Catchot notes. There, a different challenge has emerged, as tobacco thrips have evolved resistance to the neonicotinoid insecticides used against them. Growers are eagerly awaiting a GE cotton variety that will fight thrips with Bt proteins. (See more here: https://www.dtnpf.com/…)
Catchot and his Midsouth colleagues also recommend the annual use of corn seed treatments. "We can, year in and year out, very clearly show big benefits to seed treatments in corn in our region; it can [commonly] be 10 to 20 bushels, depending on the year and the pest," he said. (See more here: https://pubmed.ncbi.nlm.nih.gov/…)
In southern soybeans, the advantage to treatments is slimmer. That is most likely due to the soybean plant's storied ability to compensate for early season stand damage, Catchot said. There, Midsouth researchers see an average yield bump of around 2 bushels per acre, much like their northern colleagues. (See more here: https://pubmed.ncbi.nlm.nih.gov/…) But between heavy annual pest pressure and the prevalence of early planted soybeans, Catchot said Southern soybean growers tend to find treatments a worthwhile investment -- and he mostly agrees. "For some people that's not worth the added front-end loading cost; but for most it is," he said.
For Catchot, the key is that soybean growers still have the option to buy soybeans without seed treatment. As essential as he finds corn seed treatments for Midsouth growers, the lack of untreated corn seed access is not an ideal industry practice for pesticide use, he said.
"I always like growers to have a choice," he said. "I don't like leaving farmers with no recourse to do something different."
There also is the worry that overuse of seed treatments might ultimately punish growers who truly need them. "The problem is seed treatments are really important in certain agricultural systems," said Michigan State University entomologist Chris DiFonzo. "And instead the industry put them on everything to the point that they might be regulated or pulled."
ENVIRONMENTAL CONCERNS CATCH EYES
As seed treatment use has grown steadily in the past decade, farmer knowledge of the ingredients within them has declined dramatically.
The most recent catalogue of seed treatment active ingredients, compiled by University of Wisconsin researchers, tallied 263 branded seed treatment products, representing 56 unique active ingredients. Just one active ingredient, the common fungicide metalaxyl, is sold under 14 different brand names. See the full catalogue here: https://ipcm.wisc.edu/….
Insecticides and fungicides aren't the only seed treatment ingredients, either. A crop seed has become valuable real estate, with companies coating on other compounds each year, such as nematicides, plant growth regulators and microbial products marketed for plant health.
In a study published last spring, Penn State University plant pathologist Paul Esker and his colleagues found that fewer farmers than ever can name which of these dizzying array of ingredients are coated on their seed. The study found that 16% of the responding cotton growers, 35% of corn growers, 38% of the soybean growers, 43% of winter wheat growers and 57% of spring wheat growers were unable to name the branded seed treatment product used on their crops, much less the individual pesticides within them.
In contrast, these farmers were readily able to provide the names of pesticides they applied to fields later in the season, by air or sprayer, 97% to 99% of the time. (See more from that study here: https://www.dtnpf.com/….)
Hesterberg was one such farmer not so long ago, he said. He could name the seed treatment package he used -- Escalate from Beck's Hybrids -- but he couldn't name the active ingredients. For a farmer who thought carefully about every input on his farm and prioritized soil health, that didn't sit right, he recalled.
"The more research I've done, the more I've realized it's probably not a wise thing to load up seed with everything we've got every single year," he said.
Both Hesterberg and Rademacher said potential environmental costs of annual seed treatment use have also come onto their radar in recent years.
"I've got honeybees on three sides of me," Hesterberg said. "A few years ago, we had a very windy spring." The dust that abrades off seeds during planting, especially with vacuum seed planters, blew around. "One beekeeper near us, she had a huge loss," Hesterberg said. (See more on dust-off risks from seed treatments here: https://www.dtnpf.com/…).
Scientists have also raised concerns over their impact on non-target pests within agricultural fields. Among the first to raise questions was a team of Penn State scientists, who found that slugs that fed on neonicotinoid-coated seeds and seedlings survived but became toxic to their natural insect predators such as spiders and beetles. (See more here: https://agfax.com/…).
Since then, researchers have published dozens of studies showing negative impacts on pollinators, aquatic insects and soil-dwelling insects. Most recently, a meta-study from University of Missouri scientists and the USGS found that neonicotinoids negatively affected the abundance, behavior, condition, reproductive success and survival of 14 classes of beneficial insects. See more here: https://esajournals.onlinelibrary.wiley.com/…
Minnesota state regulators found that 12 species of birds and 14 species of mammals also readily consumed spilled treated seed. In March, the Minnesota Department of Natural Resources released the results of analyzing 800 deer spleens from the 2019 hunting season in the state; they found that 61% tested positive for neonicotinoids, albeit at low levels. South Dakota State University scientists, inspired by abnormal deer behavior, conducted a study that same year that found that contact with "field-relevant" doses of imidacloprid could negatively affect white-tailed deer's behavior, size and development. See more here: https://www.sciencedirect.com/…, here: https://www.dnr.state.mn.us/…, and here: https://www.nature.com/….
Another growing area of concern is that neonicotinoids don't always stay put on the seed even when in the soil. Studies by both industry and academics have determined that only 5% to 20% of neonicotinoids are taken up by the plant, with the rest free to leach into soil and water. "There's a lot of leaching because they are highly water-soluble compounds," explained Michelle Hladik, an environmental organic chemist with the USGS. "If there is rain or irrigation, neonicotinoids can dissolve and can be transported down into the soil and groundwater, potentially. Or if there is a big rain event, they could flow over land or, in an agricultural field, go into a tile drain."
As a result, neonicotinoid insecticides are surfacing in American waterways with increasing frequency, from streams and wetlands to municipal water supplies. In one recent national study piloted by Hladik, scientists found them in 53% of streams sampled across the U.S., from California to Delaware. The Midwest is an area of particularly frequent detections; one of Hladik's studies sampled streams in Iowa from March to May of 2013 and found clothianidin in 75% of the samples and thiamethoxam in 47%. Pesticide concentrations were found in every sampled stream, and their concentrations climbed after rainfall events, suggesting they were washed out of treated fields. See more here: https://www.usgs.gov/… and here: https://ca.water.usgs.gov/….
Imidacloprid is especially persistent in the environment. A USGS study this year found the compound in river water at concentrations above EPA-established risk levels hundreds of times at 81% of the river sites sampled, earning it the study's dubious honor of having "the most widespread potential toxicity." (See the study, which assessed 221 pesticides in water, here: https://www.sciencedirect.com/…).
"It's not just an agriculture thing," explained Hladik. "We can find neonicotinoids in urban areas, too. But when we find them in areas like the Great Lakes or Iowa -- where they are used for agriculture -- we do see an increase in concentrations following the crop year, especially for clothianidin and thiamethoxam used in seed coatings."
One 2016 study Hladik worked on with University of Iowa scientists found imidacloprid, clothianidin and thiamethoxam in the university tap water samples collected from May to July. Not only did the compounds survive certain water treatment processes, but in another study, the same group of researchers warned that neonicotinoids have the potential to form even more toxic metabolites (breakdown products) after undergoing the chlorination processes common in drinking water treatments. See more here: https://ppc.uiowa.edu/… and here: https://cheec.uiowa.edu/….
In emailed responses to DTN's inquiries, EPA said the agency is not concerned about these exposures, for either humans or animal life, based on their risk assessments for neonicotinoids, which rely on modeling. "The levels found in American waterways are much lower than modeling estimates used in the [EPA's] human health and ecological risk assessments," the statement read. "Therefore, EPA considers the drinking water and ecological exposure estimates to be protective overestimates of actual exposure."
Others are less confident in the safety of these exposures. A recent study by Center for Disease Control scientists found that half of the U.S. population had detectable concentrations of at least one of the six neonicotinoids or their metabolites, with children aged 3 to 11 seeing the highest concentrations. Among the most commonly detected insecticides were acetamiprid, commonly used in vegetable and fruit production, and imidacloprid, which is used in both agriculture and consumer products. Clothianidin and thiamethoxam, common seed treatment ingredients, were also detected. (See it here: https://pubmed.ncbi.nlm.nih.gov/…).
Melissa Perry, a George Washington University public health researcher who studies pesticides' effects on human health, said this type of scrutiny is long overdue, as neonicotinoid use has grown rapidly the past two decades. "This kind of surveillance is absolutely essential," she said. "Neonicotinoids came onto the market very quickly and they pose a pesticide use -- systemic insecticides -- that we don't have good, established ways to evaluate for effects on the environment and human health. It's as if we're waiting for problems to emerge and, in the absence of immediate hazard, we're assuming they're safe. And that's not a justified assumption to make."
TREATED SEED DISCARDS
One such problem emerged recently in Mead, Nebraska, at a now-idled ethanol plant called AltEn, kicking off the latest environmental concern around seed treatments: the fate of leftover treated seeds.
For five years, the plant accepted millions of bushels of leftover treated seed from most of the country's leading corn seed companies to make ethanol. The plant's mishandling of the contaminated ethanol byproducts (DDGs) and wastewater slowly polluted the surrounding area, sickening wildlife and killing bees. The plant has been shut down, but huge piles of DDGs and discard treated seed remain, with pesticides and fertilizer occasionally running off into neighboring surface water, as seed companies race to clean it up. (See more from DTN: https://www.dtnpf.com/… and here: https://www.dtnpf.com/….)
EPA, which has been tangentially involved in the cleanup, told DTN in an emailed statement the region around the ethanol plant is currently at serious risk from the pesticide pollution there. "…[T]he wet cake and wastewater produced by the Nebraska ethanol facility represent a level of contamination that has no uniformity or limit on the number and amount of pesticides present," the statement said. "EPA cannot conclude that land application of the wet cake or discharging the wastewater onto land will not result in unreasonable adverse effects on humans or the environment."
It remains hard to know whether the AltEn ethanol plant pollution is a disastrous one-off mistake or a symptom of a larger problem. Seed companies and the EPA have refused to estimate to DTN how much treated corn and soybean seeds have to be discarded at the end of each year, nor where the seeds are sent.
And EPA claims ignorance of treated seed disposal practices in the industry, directing inquiries to state regulators. Treated seed is regulated under individual state "seed laws," but those mostly address labeling requirements and are focused on the seed, not the pesticide, explained Patrick Jones, president of the Association of American Pesticide Control Officials. "There are no regulations in most states in either program to address the disposal of treated seed," he said.
While the federal labels for seed treatments give instructions on burying or destroying small amounts of leftover seed, there are no federal guidelines for disposing of large amounts of it. Bulk amounts of pesticide-coated seed generally qualify as hazardous waste under state laws. But for the most part, companies have created their own oversight of disposal methods, via an industry group called Pesticide Environmental Stewardship. The PES advertises a short list of acceptable destinations for treated seed: ethanol plants, municipal landfills, waste management facilities, power plants and cement kilns. See more here: https://pesticidestewardship.org/….
How much treated seed is discarded each year? DTN obtained estimates from a variety of industry sources, with most asking to remain anonymous. All settled on around 10% of treated seed as a likely figure.
Ten percent is a popular percentage for retailers and farmers to over-order, to protect themselves and customers in the case of bad weather and stand failures, explained Wisconsin's Conley, who was willing to go on the record about these estimates. "Usually a seed company suggests a farmer books 10% extra seed, just to have it in case," he said.
Based on a corn planting of 92 million acres, nearly 100% of it treated, that would leave the industry with roughly 3.8 million bushels of treated corn seed to discard each year, Conley calculated. For soybeans, based on a planting of 84 million acres and Conley's estimate of 80% treated, that would leave industry with roughly 6 million bushels of treated soybean seed to discard each year, he said.
For context, it would take nearly 10 trips for a 110-car train to move that much corn, and roughly 15 trips for the estimate of discarded soybeans.
EPA's risk assessments for neonicotinoid and fungicide ingredients do not consider any risks from the bulk disposal of treated seed, the agency admitted in a statement to DTN. Its risk assessments for pesticides are created "assuming the pesticide products are used properly in accordance with the product label and are disposed of as directed on the label," the agency wrote.
Nonetheless, the agency told DTN it is satisfied with its analysis. "While our risk assessments do not specifically consider the possibility of large accumulations of treated seed in landfills and other disposal facilities, the risk assessments do not underestimate exposure."
FUNGICIDES: THE LESSER KNOWN PESTICIDE
For as much research has sprung up around neonicotinoid seed treatments, their partners on the seed -- fungicides -- have been far less scrutinized.
While plenty of research exists on how fungicides behave in foliar applications, there is little information available on how the compounds behave on the seed. Plant pathologists contacted by DTN were largely at a loss to characterize how much fungicide might leave the seed and how it might behave in the soils or water after application.
"It's not a conversation I've had ever," admitted Penn State's Esker. "Fungicides have not been considered as closely as insecticides or herbicides."
The 2021 analysis of river water by USGS is one of few available studies documenting fungicide presence in U.S. waterways, but even there, scientists couldn't look for half of the fungicides used in the country, because of analytical limitations. Nonetheless, they found quite a few; the most frequently detected fungicides were azoxystrobin, a common corn and soybean seed treatment ingredient, and propiconazole, also used in corn and soybeans, as well as wheat and rice fields.
What does this mean for aquatic life and human health? Scientists aren't sure. A group of European and American scientists just penned a warning letter to the industry in 2019, calling fungicides "an overlooked pesticide class." They concluded that fungicides, at current use levels, do pose risks to aquatic life, particularly insects and fungi. See it here: https://pubs.acs.org/….
THE FUTURE
Following the lead of other countries such as Canada and members of the EU, some states such as Maryland, Massachusetts and New York already restrict the use and sales of neonicotinoids beyond EPA's rules. In April, the Nebraska legislature passed a bill that bans ethanol plants from accepting treated seed, in light of the Mead disaster. A similar bill is underway in the Illinois legislature.
Other states are mulling laws that would empower state regulators to fully monitor treated seed as a pesticide, unlike EPA. Vermont became the first state to do just that in 2016. The new law was written after members of the state's senate agriculture committee asked Giguere a question about the percentage of crop seeds treated in the state -- and he couldn't answer, he recalled.
"They had passed a pollinator protection bill and that's a piece of information that was missing," Giguere said. "There was a data gap."
Now Vermont pesticide regulators get reports on exactly how much seed is treated and where it goes, and there is an advisory group considering whether to require farmers to become certified applicators in order to plant treated seeds, since they are technically applying pesticides in the process.
"These steps were all part of conversations going on in the registration division of EPA 15 years ago, too," Giguere recalled. "But we are the only state with this authority currently."
Could EPA ever change how it regulates treated seed? A 2017 petition from the Center for Food Safety argues that it should.
The petition, which was submitted in 2017, represents the American Beekeeping Federation, American Bird Conservancy, American Honey Producers Association, Pesticide Action Network and Pollinator Stewardship Council and a handful of farmers. It asks EPA to remove the treated article exemption for treated seeds and fully track and monitor pesticide use via seed treatments going forward. See it here: https://www.epa.gov/….
In the four years since the petition was submitted, EPA has been silent.
In its emailed statement to DTN, the agency wrote that "The Agency is working on a response to this petition. Until the Agency comes to a conclusion, treated seeds meeting the treated article exemption criteria will continue to fall under the treated article exemption."
Emily Unglesbee can be reached at Emily.unglesbee@dtn.com
Follow her on Twitter @Emily_Unglesbee.
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