Neonicotinoid insecticides are a synthetic version of nicotine compounds produced by plants such as tobacco, tomatoes and potatoes. The synthetic version is used in agriculture to kill insect pests, and are the most widely used insecticides in Wisconsin, the U.S., and globally.

According to Ellen Voss, Climate Resilience Director with River Alliance of Wisconsin and co-coordinator of Wisconsin Neonicotinoid Workgroup, neonicotinoids are very good at killing insects, but aren’t specific to pests. In addition, Voss says, they are highly toxic, even more so than DDT.

Voss provided a presentation about neonicotinoids to a group of Prairie Enthusiasts Southwest on Saturday, March 14, at the Hildebrand Memorial Library in Boscobel. About 25 citizens attended the event.

“You might ask, what is a climate resilience director doing here. With climate resilience, we're talking about how we prepare, respond, recover and adapt to the changes that we know are coming in our warmer climates,” Voss told the group. “River Alliance’s mission started with a focus on protecting the waters, but my role has also evolved into protecting biodiversity – ecosystem, species and genetic diversity. Within genetic diversity may be things that give some members of species resistance to changing climatic factors.”

Biodiversity

Voss cited studies in global biodiversity by the World Wildlife Federation that overall diversity of marine, terrestrial and freshwater species had declined by 73% between 1970 and 2022. Freshwater species diversity had declined the most at 85%, followed by terrestrial at 69% and marine at 56%.

“We have really seen a dramatic decline in global insect populations,” Voss emphasized. “And, insects are really, really important for the health of the planet.”

Voss pointed out that insects provide a long list of what she calls “ecosystem services.” Those include pollination, dispersal of seeds, controlling populations of other insects, breaking down and dispersal of dead tissue, stimulating soil health, and more. She cites habitat loss, climate change, and indiscriminate use of insecticides are reasons for the decline.

“Use of pesticides in agriculture ramped up until about 1960, and then started to plateau in the 1980s,” Voss said. “That might seem like a good thing, but what you have to understand is that the pesticides used today are more potent and powerful, and much stronger at smaller volumes. The problem with neonicotinoids, which are used to coat almost all corn and soybean seeds today, is that their impacts are not specific to pest insects – they’re impacts are felt in beneficial insect populations as well. Neonicotinoids, for instance, are 7,000 to 10,000 times more toxic than DDT.”

Neonicotinoids

Voss said the names of the three most common neonicotinoids are imidacloprid , clothianidin and thiamethoxam. She emphasized that while their highest volume of use (90%) is in agriculture, they also appear in common household lawn and garden chemicals, as well as in treatment for fleas and ticks in common pet products. Household use sometimes creates urban hot spots.

“Neonics work as neurotoxins, they disrupt nervous systems, which make it hard for muscles, nerves and organs to communicate, and they bind permanently,” Voss explained. “Even when present at sub-lethal levels, they are still having damaging behavioral impacts on invertebrate species.”

Voss said nenonics have gained acceptance because they’re viewed as an easy, ‘one-and-done,’ prophylactic solution to pest control. But, she said that only about 20% of seed coatings actually stay to become available to the plant, with the rest either binding with soil or entering ground and surface waters, according to a study by Alford & Krupke (2017)/ Sur & Stork (2003).

According to WDNR’s Mike Miller, Water Resources Management Specialist, Division of Environmental Management for Water Quality, Monitoring Section, being water soluble means the remaining 80% results in high mobility to surface and groundwater.

“They’re very mobile in the environment, so they don’t really stay where you put them,” Voss explained. “They can persist anywhere from seven to thousands of days in the soil, and they move quickly and easily in water.”

Voss cited the decline in Mayfly hatches, which have been tracked by National Weather Service over the years. She said that it used to be the snowplows would be called out to remove Mayflies, but in recent years, NWS has described it as, “slight emergence, you’re just not seeing those giant patches like you used to.”

Widespread use

Voss said that with a lot of corn and soy, especially in the U.S, the increase in neonic use happened relatively quickly. She said that back in 2003 there wasn’t much use, but by 2006 there was quite a bit, and by 2009 basically the entire Midwest was covered.

Voss said there was a noticeable drop off in 2015, and said, “what happened that year?”

“Why did reported use go down so significantly? The answer is, it didn't. We just weren't measuring it anymore because, because a change happened to the 1972 Federal Insecticide, Fungicide and Rodenticide Act (FIFRA),” Voss reported. “In 2014, the ‘Treated Article’ clause was added, governing any pesticide that's applied to an article. A seed counted as an article, which means that they don't have as much regulatory oversight anymore. And, use of these insecticides have meant that in just 25 years, agriculture became 48 times more harmful to insect life.”

The tragedy

Voss explained that almost 100% of field corn seed is treated with neonicotinoids, and about 60% of soybean seeds.

“The tragedy here is that by the time key pest species appear in the cornfields, it's too late in the summer, so a lot of that concentration of the neonicotinoid seed coating isn't actually available to the plant - there's a mismatch in the timing, so it's not even helpful,” Voss shared. “They're being so widely used, and they're actually not providing in most cases, a benefit to the farmers. The take-home message is that the yield increases, if they happened at all, didn't offset the cost of the neonics that were used. It's expensive, and it actually isn't helping. There’s no difference in corn yield between treated and untreated seeds, and with soy, there is a decline in yield because neonics actually kill the beneficial insect predators of slugs.”

According to Syngenta and Bayer Crop Science, Wisconsin corn and soybean producers spend between $20,000,000 and $60,000,000 on seed-applied neonics each year.

Voss said that neonicotinoid treated seeds are doing more harm than good.

“A lot of money is going to chemical companies and it's actually not helping our yields,” Voss pointed out. “And, it's doing a lot of damage to the environment.”

WDNR’s Miller cited a study from China, The fate and transport of pesticide seed treatments and its impact on soil microbials, ‘Journal of Ecotoxicology and Environmental Safety,’ Vol. 290, 15 Ja., 2025. Kaiye Li a, Qing Cheng a, Chao Zeng a, Hong Shen a, Chensheng Luab, that documented that:

• most thiamethoxam applied in the seed treatment were retained in soil.
• Thiamethoxam in soil was mainly concentrated in the 0–10 cm layer from soil surface. [where it’s prone to runoff]
• Thiamethoxam modified the abundance of soil bacteria at the early growing stages.
• maize (corn) grown from pesticide-treated seeds did not lead to a higher overall yield.

Broader impacts

Voss pointed out to the group of gathered prairie enthusiasts that the persistence of the chemicals in soil can lead to problems with projects seeking to restore native prairie on former croplands.

“Any plant that comes in contact with contaminated soil will take up that chemical, and all parts of that plant will become toxic,” Voss pointed out. “So, if you're nurturing a beneficial milkweed plant in a field where corn that's been treated was grown, the plant that we know monarchs need to survive is now toxic to that monarch.”

Voss said that the further you look, you start to see impacts all across the board.

“It's pollinators, it's birds, it's people, it's deer, it's kind of everywhere,” she pointed out. “One sugar granule, which is very, very small, is enough to kill 125,000 honey bees. When you have exposure to neonics, you start to see some really big disruptions in their ability to function. They have decreased foraging effect when they're exposed to neonics, they have reduced ability to have floral learning, their ability to find the same food sources over and over again and share that information is diminished, and then also it impacts their ability to navigate. If they can't find their way to the right plants or the right food sources, that's going to have an overall impact on the amount of food that comes into the hive. And so that has impacts on reduced nursing, overall activity, and social interactions.”

Voss said that neonicotinoids have been implicated in the widely studied phenomenon of ‘colony collapse’ in bees, and is a significant factor. She said that while the impacts to honeybees has been studied more, the impacts to native bees is actually more severe.

“If we start to lose our pollinators, that has really big implications for a lot of things,” Voss said. “In terms of the global food supply, they're extremely important. So if we start to lose them, that will impact our ability to provide food for the world.”

Bird/aquatic impacts

Voss pointed out that birds are also on a rapid decline, not just in the U.S., but across the globe. She said that when researchers look at birds dependent on insects for food, the estimate is that three billion birds have been lost.

“American Bird Conservancy is one of the groups that's part of our neonic work group,” Voss told the group. “They shared the statistic that 96% of North American birds depend on insects at some point during their life cycle.”

“Neonics are showing up in our streams and in our groundwater, and that's not surprising, because they're water soluble - they like to travel in water,” Voss shared. “From a study that Mike Miller did in 2022, the ‘Statewide Stream and River Pesticide Survey,’ 72% of the sampling sites had neonic's in them, with results ranging from very low to pretty high.”

Voss pointed out that use isn’t just with corn and soy, but also with potatoes in the Central Sands Region, where sampling revealed acute toxicity levels. She said neonics are also used with other vegetable crops grown in Wisconsin.

“Mike’s study revealed that 138 different pesticides were detected in streams sampled statewide in 2022,” Voss said. “There were between 9-91 compounds detected per site, with an average of 28 compounds per site.”

Voss said that in the study, 29% of sites revealed pesticide levels chronically toxic to some aquatic invertebrates, and 10% revealed levels acutely toxic. A U.S. Geological Survey in 12 Midwestern states from 1999 to 2020 revealed that 62% of sites detected chothianidin, 41% detected imidacloprid, and 38% detected thiamethoxam.

In addition, a DATCP survey of neonics in groundwater and wells revealed that one or more neonics were detected in 17% of well samples, and 30% of the 1,137 groundwater samples taken.

“At the watershed scale of larger rivers like the Wisconsin or the Mississippi, I’m sure levels are very high,” Voss said. “We’re seeing impacts at that level, as well as at the level of our inner streams and rivers.”

Voss said that a study in Minnesota also revealed impacts to the deer populations.

“In 2019, 61% of the deer sampled had concentrations,” Voss reported. “In 2021, it was almost all the deer that they sampled, and at levels high enough to cause birth defects.”

Voss said that the chemicals are in humans too.

“We're exposed to neonics on a lot of different scales, all the time, through our private wells, through the food that we eat - some fruits and vegetables have actually have neonic levels that are above safety limits, and it's found in a lot of household products that we use in our homes. There's a study that I find pretty concerning in pregnant women, where 95% of women had detectable neonic levels, which is really scary to me.”

Is there hope?

Voss pointed out that the U.S. is really late to the game of regulating use of neonicotninoids compared to Europe and Canada.

“Back in 1999, France banned the use in food production, and more recently, in 2019, Canada has had some effective limitations put in place to curb the unnecessary use of these chemicals. What's been really effective is the ‘verification of need’ idea. In Canada, you can't just blindly apply it wherever you want. You have to prove that you need it. You almost need a prescription from an agronomist,” Voss pointed out. “In the U.S., New York has definitely led the way. They enacted an effort called the ‘Birds and Bees Protection Act.’ Starting in 2027, the law will prohibit lawn and garden uses, and by 2029 seed coatings on corn, soy and wheat will be prohibited. They're estimating that this will have an 80 to 90% reduction in levels of use.”

Similar legislation has been enacted in Vermont, and introduced in Minnesota. New Jersey, Maine and Nevada have banned neonic use in lawn and garden products. Restricted use laws are in place in California, Colorado, Connecticut, Maine, Massachusetts, Maryland, Mississippi, New Jersey, Rhode Island and Washington.

“In Wisconsin we have opportunities to address the problem,” Voss told the group. “This could be accomplished through establishing state groundwater standards through DHS and DNR, voluntary efforts such as preventing use on state-owned lands, and common sense legislation.”