Agriculture gains pose aquatic life concerns

By Mark H. Stowers

Land and water harmonize to compose Michigan into an outdoorsman’s paradise with lakes and streams and rivers bordered by four of the Great Lakes – Superior, Huron, Erie and Michigan. Much like a Lennon and McCartney masterpiece, land and water create the paradise but contaminants from residential, industry and agriculture threaten to break up that harmony.

For generations, insecticides and pesticides have been used to control and manage the wilds of Mother Nature, her creatures, and the diseases that threaten crops. Scientists have studied and produced mass insecticides that, in the early years, were as simple as elemental sulfur, arsenic compounds, and plant-derived substances like tobacco, herbs, and pyrethrum. Later, synthetic organic compounds such as DDT and 2,4-D were introduced. Each one represented a step forward as being better, more targeted, and used in much smaller, more specific doses. In the 1990s, neonics (pronounced "Nee-oh-nicks"), also known as neonicotinoids, were developed as insecticides and seed coatings for crops such as corn and soybeans. As science created more precise insecticides, their popularity and usage increased. The neonic chemical Clothianidin is used as a coating on corn seeds, and Imidacloprid is applied on soybeans. Thiamethoxam is used in both.

While improvements in precise insecticides are a benefit to agriculture, scientists are now realizing that there are downsides with impacts on the surface waters – lakes and tributaries – and aquatic life.

Neonics interfere with the nervous system of insects by binding to and overstimulating nicotinic acetylcholine receptors in nerve cells. This overstimulation causes uncontrollable shaking, twitching, paralysis, and ultimately death in insects.

A Trout Unlimited magazine article stated, “Neonicotinoids quickly became the most widely used group of insecticides in the world, and their popularity is only increasing. Similar to nicotine but synthetic in composition, they were developed as a safer alternative to the previously used organophosphate and carbamate insecticides, which were known to have harmful side effects on humans and other mammals. They are applied directly to plants or use as seed coatings, allowing absorption into the plant tissues, targeting pest species that could infect the crop.”

These new insecticides are made to harm and kill insects like sap feeders – such as aphids, whiteflies, and planthoppers. Neonics also target beetles (including white grubs), fleas (found in both cat and dog flea/tick collars), wood-boring insects, and certain flies that can invade and damage Michigan row crops.

Neonics have other broad-reaching and unintended effects. Most often they are associated with the decline in pollinators and birds. The insecticide isn’t selective in its target when it spreads beyond the turnrow. Invertebrate insects, which fish feed on, are affected by neonics, including mayflies and midges. The insecticide can become a two-edged sword to aquatic life by first eliminating a crucial level of the food chain for fish and other aquatic organisms and could possibly stunt growth. Second, if these insects have ingested neonics and are then eaten by fish, it could pose a problem, although scientists have concluded that most mammals and many vertebrates are not sensitive to neonics because they lack the same receptors.

The Trout Unlimited article also highlighted a case that demonstrates this. Near Lake Shinji in Japan, farmers started using neonicotinoids on their rice fields in 1993. Within a year, the food web made up of arthropods like crustaceans and zooplankton collapsed. By 1994, two commercial fisheries — aquaculture for eel and smelt — also fell apart. Neither has recovered. In 2015, a nationwide review of 48 streams, both urban and rural across the U.S., detected at least one neonicotinoid in 53 percent of the samples. Positive detections were most common in heavily farmed areas, especially in the Midwest, but were also found in small streams in California and large urban regions.

Another issue often seen in risk evaluation is that the organisms used for testing effects may not have been the best choice for understanding ecosystem impacts. When the EPA approved tests in the early 1990s, they primarily used water fleas (Daphnia) to measure the toxicity of neonicotinoids, but we now know these are much less sensitive to toxicity than many aquatic insects, sometimes by hundreds of times. This means that the limits set by the EPA do not protect many aquatic insects.

Recent findings have detected the presence of the chemical in Michigan surface waters.

“For aquatic insects, particularly important trout foods like most mayflies, caddisflies, and stoneflies, just the presence of neonics in the parts-per-billion range is lethal,” said Jack Williams, the former director of the Trout Unlimited science team, who has been reviewing the impacts of neonicotinoid pesticides on aquatic insects and their effects on trout. 

Emily Smith is a policy manager for the Michigan Environmental Council. The northern Michigan native has been there three years.

“In Michigan, we've got 20 percent of the fresh water in the world. My understanding is that neonics are very pervasive,” Smith said. “A lot of research needs to be done on the total effects for human health.”

Michigan farmers, who grow various crops like potatoes, wheat, corn, and soybeans, know that crop loss caused by insects or weeds can be just as damaging. Lost profits can lead to unpaid mortgages, farm loans for planting, equipment, and crop inputs. However, farmers have limited options. Corn and soybean seeds are treated with neonicotinoids and coated with fungicides and insecticides to protect against pests and diseases. Seed companies are responsible for providing treated seeds. The seeds available to farmers come already coated with these treatments.

Calls to Bayer Crop Science and messages seeking more information have not been returned at press time.

According to the Trout Unlimited story, “From 2009 to 2011, the EPA estimated that 3.5 million pounds of the insecticide in various forms – acetamiprid, dinotefuran, clothianidin, imidacloprid, thiacloprid, and thiamethoxam – were applied to 127 million acres of agricultural crops each year, not counting the rapidly increasing use of seeds coated with neonicotinoids, which farmers use to proactively prevent pests. When you include neonicotinoid-coated seeds, the Xerces Society estimates that more than five million pounds of these chemicals were used in 2011 alone.”

The two main producers of neonicotinoid products are Syngenta, based in Switzerland and Chicago and Bayer, based in Germany and New Jersey.

Recent studies have shown the presence of neonics in Michigan waterways, particularly those near large agricultural businesses where corn and soybeans are cultivated. Michigan State Extension field crops expert Chris DiFonzo explained more about neonics in corn and soybeans.

“Almost every acre of corn seed is treated. It comes that way. The grower does not have a choice. Unless it’s an organic grower, but regular field corn is 99.9 percent treated at the company level,” DiFonzo said.

Soybean growers do get more of a choice according to DiFonzo.

“We're 50-50. Fifty percent are treated with a neonic and a fungicide. There's always a fungicide along for the ride. And then maybe 50 percent of the acres are probably the fungicide alone,” she said.

In 2025 in Michigan, there were 2.25 million acres of corn planted and 2.2 million acres of soybeans. She noted that there aren’t many aerial applications of neonics in Michigan. It’s almost all at the seed level. DiFonzo also explained that each new chemical created and tested replaces a much harsher and more dangerous one.

“When it was introduced, it replaced organophosphate insecticides, which were originally developed from nerve gas – essentially, World War II nerve gas – and were extremely toxic to humans. They especially affected the developing brains of children. So, they were introduced just at the right time. People often forget this was to replace a class of insecticides that was widely used on fruits and vegetables. Organophosphates are mostly phased out now. We replaced a very large human health problem, a group of insecticides that was responsible for that, with neonics,” DiFonzo said.

But with each replacement, nothing is perfect and not without impact.

“The way that the older genophosphates were used, they were sprayed on or just dribbled into the ground. With corn and soybeans, the neonics are placed right on the seed. It's a very targeted kind of application,” DiFonzo explained.

“In Michigan, the corn farmer has no choice,” she said. “It is put on with fungicides and nematicides and other products as a package. And part of it is for pest control, and part of it is for convenience. Because if I had just paid $350 for a bag of seed and then something ate it, I would come back to the company and complain, and then the company would have to pay out again. It's insurance in corn. There would be times where you would judiciously, you probably do need it. You're planting early when the seed sits in the ground for a while. You're planting into soil that's kind of wet and maybe you think you might have pathogens and some other insect issues, or you have grubs, or you have wireworm. There are those kinds of cases.”

With fewer insects in Michigan for soybeans, entomologists have agreed that there is less need for seed-treated soybeans, according to DiFonzo.

“We have very few insects in soybeans at planting. The insects we do have, we recommend spraying for them if they are present. And there'd be very limited cases where you would need seed-treated soybeans. It's more of a choice at that point. The grower can get their seed treated or not in soybeans. We have recommended that for the average farmer with good ground and no pest pressure, they not have the neonic on their seed, that they don't need it, mostly. But that's not how seed is sold. Seed is sold as package deals, where farmers get deals from companies or, they get a package seed treatment. It's easier for the company to put the five things on the seed than to have you want only the four. The farmer is at the mercy of how seed is produced. There's a convenience of scale that we have in almost every industry.”

With seed costs being one of the most expensive purchases, farmers have to accept the coatings, especially with corn. A bag of treated and coated seed that will plant two acres costs up to $350. Spread that cost over 1,000 acres, and a farmer has a $175,000 planting bill right out of the gate to start the growing season before any fertilization or other crop inputs. The current corn price is $4.15 per bushel and last year’s average yield was 181 bushels per acre. That’s $751 per acre and those 1,000 acres would gross $751,150. But when equipment costs, fuel, insurance and employee costs are deducted that number can quickly change to a deficit. A natural disaster of rain or other weather can cause a farmer to replant some acreage, cutting deeper into the projected return on investment.

“Corn is an untested system because it all comes treated. A grower can't even order an untreated seed or non-neonic seed to see what would happen,” she said.

And even as data and testing is coming out in the past 10 years showing neonics in water samples, prior chemicals would have had a much higher showing in decades past.

“If you looked at what was in water 30 years ago, you would have picked up organophosphates and carbamates, which is what we used to use. If you put stuff into the soil, the soil moves, and water moves. Once it gets to the aquatic system, what does that mean? That I don't know. But they don't bioaccumulate. DDT bioaccumulated. But neonics, the pyrethroids that we use, none of those things bioaccumulate. They can't move up the food chain and get larger amounts, like we did with the old organochlorines. That's another old one we phased out. Organochlorines were replaced by organophosphates and organophosphates were replaced by neonicotinoids. We're always doing better,” DiFonzo said.

The science of the insecticide is “If there's residue on a crop and you ate that, you would be exposed to that residue, and then you'd probably break it down in your body and pee it out or however it breaks down in the body. But it wouldn't stay long-term in there,” DiFonzo said. “That’s part of the EPA registration package. If something bioaccumulated, it doesn't get registered.”

With the millions of acres planted, neonicotinoids go in the ground in March, April, May on all those acres just in those two crops.

“There will be off movement through water for a period of time that could be detected,” And according to DiFonzo, “Michigan is the biggest corn seed producer in the world. Southwest Michigan and Northwest Indiana are the largest seed production areas for corn in the world. There are 60 growers producing 25,000 female acres.”

Looking at the aquatic impact of neonics, there is neonic contamination in Michigan waters, according to a June 2025 National Resource Defense Council (NRDC) report. Michigan surface waters – including tributaries – are often contaminated with neonics year-round at levels above safety thresholds for aquatic ecosystems. Also, a US Geological Survey data shows 75 percent of samples from major tributaries contain detectable neonicotinoids. The Saginaw River had 12 samples taken and 100 percent of them detected clothianidin. Of the 24 samples taken for imidacloprid, 33 percent detected it. The 12 samples for thiamethoxam only had 25 percent of the samples showing the chemical.

The Clinton River sampling recorded findings of imidacloprid only but had some of the highest levels recorded in 2001 with 985 nanograms per liter. The numbers decreased in 2018 to 809 and 723 in 2021. The nearly 82 mile river that ends in Lake St. Clair also includes the upstream tributary Paint Creek, the only designated cold-water trout stream in the state. No tests for neonic residues were conducted at Paint Creek though.

In 2023, Michigan’s Department of Agriculture and Rural Development (MDARD) collaborated with the Department of Environment, Great Lakes and Energy (EGLE) to test for neonics in state surface waters. The USGS report explained that neonics were detected at exactly half of the sites and the bulk of detections were from the three neonic active ingredients in seed treatments. The sampling dates of May, July, September and November correlate with the agriculture season. Optimal planting is early to mid-May for corn and soybeans. Peak residues are expected after the first rainfall after planting and then in July and in November during harvest after rain.

Kevin Cox, supervisor for the Water Toxins Unit with EGLE and Dawn Roush, a supervisor of the Lake Superior, Huron and Erie Unit, have been investigating emerging contaminants. Roush has more than 24 years of experience, while Cox is picking up the work first begun by Dr. Sarah Nedrick, formerly with EGLE. The initial USGS survey kickstarted their work.

“We saw that there were some detections of some of these, particularly in the Saginaw Watershed where the USGS did a few sample sites there,” Cox said. “Seeing some of the information from that study and reviewing a bit on just the overall use of these neonicotinoids and concerns about particular pollinators, how much would we see in our surface waters?”

EGLE conducted a comprehensive study running from August of 2021 to October of 2021; then restarted it in April through July of 2022. With 14 sites sampled with both single time water grabs and passive sampler devices that collect chemicals over a 28-day period.

“We tested for six different neonicotinoids, both in the passive samplers and in the grab samples. And we found really the big three that we were anticipating seeing fairly frequently. That's imidacloprid, clothianidin, and thiamethoxam,” Cox said.

His unit also set out to determine what an appropriate level of contaminant would be.

“We wanted to see what value or concentration would impact aquatic life in our surface waters and so these values end up coming out pretty low,” he said. “Imidacloprid was 29 nanograms per liter. That's a pretty low number while clothianidin was 81 nanograms per liter for the chronic value and thiamethoxam was 280 nanograms per liter. Again, each compound has slightly different toxicities. And what we found was that in seven of the 14 sites, imidacloprid at one time would exceed that chronic number. It’s exceeding the value that could show impacts. So, in this situation, mayflies and midges are the most sensitive, and that's how we based our number for all three of them.”

The EGLE report states that seven sites out of the 14 that have exceedances for imidacloprid as a pollutant, as an emerging contaminant in surface water.

“It was a little disheartening to have half the sites with a number above. We do also at times look at human health data. But in this circumstance, the pesticide, the imidacloprid, is really targeting insect species. Insects are much more sensitive than people. If you look at some human health values in other states and locations and EPA, they're orders of magnitude are above where you're seeing impacts on the aquatic invertebrates,” Cox said.

The survey showed the cloth and maximum concentrations were also two to five times higher than what was seen previously. Roush pointed out there is an agriculture presence in the watershed and the pesticide impact was anticipated.

“It gets into the water from runoff, and it can be impactful to the macroinvertebrate communities in those waters if there's high enough concentrations,” she said.

Roush also works with Region 5 EPA and other states in the Great Lakes region looking at emerging issues and neonics have been part of that discussion.

“We primarily monitor waters that go to those three Great Lakes, but we also have some statewide efforts, too. One thing we have is the Water Chemistry Monitoring Program, which is supervised within my unit. We have 250 sites that were chosen randomly throughout the state in rivers and streams. And we look at the 50 of those a year over a five-year period. And so, each year, that's a random snapshot of the state. Every year there are 50 across the state. That way, every year we can get a snapshot of what's going on.”

With 26 routine parameters including phosphorus and nitrates, chloride, mercury and lead are looked at every year.

“The sixth year, we go back and look at those 250 again and we also get trends over time. Because this is a statewide effort every year, it's nimble, and it's very easy to add an emerging issue to it. We've done it for E. coli. We've done it for selenium. And then we decided this was a great opportunity to investigate neonics. Neonics, because while we hear a lot about agriculture, my question comes back to, what are neonics typically looking like through the state and our rivers and streams?”

She explained: “Anecdotally, I feel like you hear that they're definitely used in agriculture. So, we look in agriculture area. We conduct these targeted studies, and I think that's very important. But it's also important to say, what do they typically look like in the state? Where are we typically finding them? How often are they exceeding a threshold? Is harmful to aquatic life? So that's where I come in. The group that's in my unit oversees the study. We have contractors who collect the data. The first year we collected neonics was in 2023.”

It took some time to figure out how to conduct the study pertaining to who would conduct the lab analysis, what costs would be and where to find the money. The study has 105 sites each year. The study is looking at neonics but has focuses on such contaminants as PFAS, e-coli and microplastics and selenium.

The sites in Oakland County included Kearsley Creek where dinotefuran was found in 2023, Sashabaw Creek where fipronil1 was found in 2024, the Huron River where imidacloprid was found in 2024 and Trout Creek where acetamidprid, dinotefuran and imidacloprid were all found in both 2023 and 2024.

“The sites are visited four times the year they are sampled, once in May, July, September, and November. All four Oakland County sites had at least one pesticide detected at least one time. Of the pesticides in this analysis, Michigan has water quality standards for Clothianidin, Imidacloprid, and Thiamethoxam. Of those three, Imidacloprid was found at two of the four sites in Oakland County,” Roush said. “And while it was detected, Imidacloprid was not found higher than the acute value in any samples at either site. At Trout Creek, Imidacloprid was found above the chronic value during one visit; however, two or more detections above the chronic value are required to be considered exceeding Michigan's chronic water quality standards that protect fish community and other indigenous aquatic life and wildlife designated uses.”

Cox noted that “while we can point out and with our reports, like we generated for the Saginaw, and then as Dawn’s group continues to gather data, we want to raise awareness in terms of making changes to that effort across multi-agency multi-government and public trying to move the needle.”

There is enough evidence in the 105 sites study, according to Cox, “where we've seen at least one of the pesticides we're looking at 46 times, so almost 50 percent of the time, That, to me, shows that there's an issue out there. And then a total of nine sites, so almost 10 percent of the sites, you're seeing either Clothianidin or Imidacloprid or both exceeding that threshold.”

The duo can only pass their findings up the government ladder, but EGLE doesn’t have the authority to change pesticide labels. Only the United States Department of Agriculture and the EPA can make those determinations when they approve pesticides. And the information used to make determinations is largely supplied by the manufacturer of the neonics.

“Even if they're following the uses, we're still seeing these compounds exceeding our water quality values. Maybe those labels need to be adjusted, but again, we don't have the authority to dictate what's approved and gets put on those differently. And again, the farmers are just following the instructions and planting those seeds and those seeds and uses have been approved by the labeling for that pesticide use. Our job is to look for it because you can't manage something if you don't monitor for it.”

According to Cox, the half-life of the neonics used in Michigan are up to a year.

“It's not an immediate breakdown when it gets released in the environment, like some chemicals. It sticks around for a little while, but not like the level of PFOS where PFOS sticks around in the environment for a real long time,” he said. “It's really important for a state agency to target studies like we did in Saginaw. And then also ask those statewide big-picture questions.”

Dan Raichel, director of Pollinators and Pesticides for the Natural Resources Defense Council, is an attorney by training and has been involved with neonic since becoming aware of the chemical’s endangerment to bees.

“There's only one factor that maps with that sudden spike of losses, and that's the sudden uptick in use, the massive uptick in use of neonicotinoid pesticides, or neonics for short, which are likely some of the most potent insecticides ever created and used on the largest scale annually in American history,” Raichel said. “And so, you add that together and you have some of the most ecologically destructive pesticides since DDT.”

He further stated, “it's not just the seed, but it's the plant as well. Neonics were the first systemic insecticides. And what that means is they are designed to permeate plants. They get into the leaves, the roots, the pollen, the nectar, everything, with the idea being they make the plant itself pesticidal. So that allows people to paint them, literally paint them on crop seeds, with the idea being as that seed is growing into a plant it soaks up the poison or the toxin, the active ingredient, through its roots and makes the plant toxic. The issue is only two to five percent of that active ingredient gets into the target plant. The other 95 plus percent stays in the soil where it persists for years and years and years. And the issue with neonics is that systemic activity. Basically, what allows them to get sucked up into the plant is that they are very water-soluble.”

When the rains come, according to Raichel, “those neonics are moving through the soil, they're contaminating new soil. If that new soil has wild plants in it, they soak up the pesticides, they become toxic. If there is a water supply nearby, that surface water, ground water, that water supply becomes polluted. And because they're persistent for several years, what happens is year after year use of these seed treatments, you get a buildup of toxicity in the soil. Again, that's expanding into every nook and cranny of the ecosystem every time it rains.”

Quoting research from a Cornell University study, Raichel noted, “In climates like Michigan, the data shows that these seed treatments provide no net income benefits for farmers. So very rarely are you getting a yield benefit from using a seed coating, and even in those rare cases that you do, that additional cost of having treatment on the seed versus the benefit, economically, it's a wash. This is research that's come out all across the United States, across the Midwest that Cornell actually put together.”

He also explained the international significance of neonics and what other countries are doing.

“Europe did prohibit the three main neonics, the ones used as seed treatments, in 2013 they expanded the ban to just about everything in 2018. Other jurisdictions have been a little bit more surgical. The Canadian government enacted a policy in Ontario, too, whereby farmers, if they wanted to use a neonic coating on their crop seed for a field crop seed – corn, soybean, wheat, other small grains – would need to get a prescription from their agronomist stating it was going to treat a legitimate pest problem. Because, again, what the research was showing is that these were not providing economic benefits, they were being used on all crops, basically prophylactically. That would be like taking an antibiotic now, just in case you might get sick in December. With the prescription requirement, we saw neonic use rates drop in Quebec from 100 percent on corn, 50 percent in soybean, to less than 0.3 percent in corn and zero percent in soybean in a matter of years without any switching to more harmful alternatives or associated crop loss. In fact, crop production has been either flat or up since those rules went into place. And so that model has also been copied in the United States.”

Even with the research, the Michigan Department of Natural Resources “boots on the ground” with fisheries have not seen damage to Michigan fish worth noting according to Cleyo Harris, a DNR fisheries technician.

“It's not something that's on our radar as far as sampling it. If we did anything, it would just be collecting fish for EGLE to test,” he said.

The 2025 Michigan Health and Human Services Eat Fish Safe Guide doesn’t list neonics as a contaminant found in any fish across the state. The guide lists mercury (usually a runoff chemical from golf courses and lawns), PFOS, and PCBs. MDHHS tests filet samples of fish taken from Michigan’s lakes and rivers to find out which fish are safer to eat. The Eat Safe Fish Guide lists the fish that have been tested, along with the safe amount to eat.

“The history of pesticide use shows that we keep replacing pesticides with better options. That’s really the truth. We used to use arsenic as our first pesticide. We continue to replace, replace, replace. And now we have neonics, which don't have many of the health effects on humans. However, they cause pollinator issues and may enter water, affecting non-target insects due to their widespread use. And why are they so broadly used? Because they replaced many harmful substances on large areas of land. So, we need to keep that perspective in mind. We do our best to replace bad with better but better isn't always best. We're always working toward that,” DiFonzo said.