By Jeanne Arnts, NC State Extension Master Gardener^SM volunteer of Durham County

There are 3 billion fewer breeding birds in North America than in 1970, which is one-third of the total bird population that existed 55 years ago.¹ Most of us enjoy songbirds, but their value is much more important than bringing joy into our lives; they are an indicator of the health of our environment and their drastically declining numbers raise an urgent alarm about the precarious health of our planet.² Just as canaries warned coal miners that conditions in mines were life threatening, the decimation of bird populations is warning us that our life on earth is at risk. Coal miners quickly left the mine when the canaries began keeling over but, unlike the coal miners who could exit the mine when conditions threatened their survival, we have nowhere else to go. Therefore, we need to take action.

Photo of chickadee with caterpillar. It requires 6,000-9,000 caterpillars to raise one brood of
chickadees to fledglings– (Image credit: New Hope Bird Alliance, Will Stuart)

And it is not just birds that are declining. In 2019, Biological Conservation reported that 40% of all insect species are declining globally and that a third of them are endangered.³ More recently, researchers established that insect populations worldwide have declined by 50%. Because 90% of terrestrial birds rely upon soft-bodied insects, mostly butterfly and moth caterpillars, to feed their nestlings (baby birds cannot digest seeds). This drastic decline in insects significantly affects bird populations as well as those of reptiles, amphibians, fish, and other wildlife that depend upon insects to survive. These startling statistics ring true to those of us who are old enough to remember “the windshield effect”. In the 1950’s and 60’s, insects would swarm around car headlights in the evening. At every stop at the gas station, the attendant would clean the windshield of the multitude of dead insects. In the 2020’s, the only time I clean my windshield is at the car wash.

Photo of Goldenrod Soldier Beetle-a beneficial insect. (Image credit: Jeanne Arnts)

Most researchers attribute bird and insect decline primarily to habitat destruction, climate change, and insecticide use. I am going to address just one of those issues: Insecticide use, specifically a class of fifteen systemic insecticides known as neonicotinoids (“neonics”). Introduced in the early 1990s, they are now the most widely used insecticide in the world; in the US, they are used on 150 million acres of agricultural land, including 90% of corn crops, 50% of soybean crops, and extensively” on cereal and oil crops, as well as on fruit and vegetable plants. S.D. Frank, an entomology professor at NCSU, noted that “transmission through simple food chains portends widespread, undocumented transmission into entire food webs” with disastrous consequences for the health of our planet. ⁴

When neonics were introduced, they were considered a panacea, as plants no longer had to be sprayed or dusted—the insecticide was embedded in the seed. Today, neonics are also applied as a spray to the leaves; as a soil drench around the base of the plant; or, by a trunk injection on trees. They can be applied along with other seed treatments and offer the advantage of being less expensive than using multiple treatments for pest control.

Effects of Neonicotinoids on Pollinators, Birds, and Other Wildlife

Most research has focused on the effect of neonics on pollinators and other insects, but neonics also affect bird populations. Birds eat the seeds of plants and they eat the insects that have sought
nourishment from the leaves. This is especially true in regard to caterpillars, which are the primary food source for terrestrial nestlings. In a review of 200 studies, including 2,800 pages of industry research obtained under the Freedom of Information Act (FOIA), the American Bird Conservatory concluded that a single seed treated with neonics is enough to kill a songbird. Smaller amounts can significantly reduce fat stores of birds as well as affect their migratory pathways and reproductive capacity.⁵

As systemic insecticides, neonics affect every part of the plant: the buds, leaves, pollen and nectar, with devasting neurotoxic effects on the caterpillars that eat the leaves of the plants, the pollinators that seek nectar from the plants, and the bee larvae that are fed the pollen.

Although neonics fed to bees in laboratory settings can kill them outright, the levels permitted in agricultural plants limit neonics to a subtoxic level in the pollen and nectar of the plants. Sub-lethal exposures, however, threaten bees—our primary pollinators in multiple ways. It reduces reproductive capacity, impedes their ability to find their way back to the nest, reduces larval survival rate, and reduces olfactory response, which is required for finding nectar-rich plants.

While regulations limit the toxicity of neonics used on food crops, ornamental plants may have as much as 30 times the limit allowed for agricultural crops. A 2017 study reported that 70% of ornamental plants are treated with neonicotinoids.⁵ A 2022 study reported that neonics were found in each of the 33 milkweed plants that were purchased from commercial nurseries across the US.⁶ Sadly, gardeners who planted milkweed to support dwindling Monarch populations were inadvertently contributing to their demise.

Eastern tiger swallowtail on Carolina lily (Lilium michauxii); Sparkling Jeweled Wing Damsel fly; Speared Dagger moth caterpillar (Image credit: Jeffrery Pippen)

The European Union placed significant restrictions on specific neonicotinoid chemicals in 2013 and in 2023 the European Court upheld the ban and eliminated loopholes that allowed for their continued use. Despite EPA research documenting the toxic effects of neonicotinoids, they are still used widely in the US on both agricultural crops and ornamental plants. However, since 2020, New York, New Jersey, Vermont, Maine, and California have placed some limits on neonic use.

Beyond neonics impact on terrestrial life, aquatic ecosystems have also become contaminated. Neonicotinoids are water-soluble and can leach from treated soils into streams, rivers, and groundwater. Once in aquatic environments, neonics harm aquatic insects that fish, frogs, and other amphibians rely upon, leading to the decline of those populations and disrupting the entire aquatic food web⁸.

Do Neonicotinoids Have Harmful Effects on Humans?

One reason for neonics’ widespread use is that they have been determined to have low mammalian toxicity. Bayer, a neonic manufacturer, issues company reports in which they espouse the effectiveness of neonicotinoids use on agricultural crops and report low toxicity of neonicotinoids to mammals and humans.⁸ Because neonics have been considered safe for human consumption, they are pervasive in our food supply. A study conducted by the American Bird Conservatory and the Harvard School of Public Health in 2015 found neonics in more than 90% of food samples tested from the US Congressional dining halls. According to the study, most foods contained multiple different neonics, with fresh squeezed orange juice and green peppers having the highest number.⁹

Unsurprisingly, the signs and symptoms of acute nicotinoid poisoning are like those of nicotine poisoning: nausea and vomiting, increased blood pressure and heart rate, and loss of muscle control, among other symptoms. The EPA has received over 800 reports of acute poisoning since 2018, but those are primarily limited to farmers and landscapers who have exposure through application of chemicals. There is rising concern, however, about the subtoxic effect of neuro-toxic chemicals on human health through food, especially its effects on neurological development. ¹⁰

A study published in an international environmental journal reported associations between chronic neonic exposure and the development of adverse neurological and developmental outcomes in young children.¹¹ Julie Daniels, PhD, an epidemiologist in the UNC Gillings School of Public Health, whose research has focused on neuro-developmental disorders in prenatal development, noted that it is not possible to implement the type of experiments on humans that have been done on insects to prove a causal effect. Dr. Daniels stated that given the pervasive use of neonics in agriculture and their persistence in the environment, there is cause for concern.¹² Most researchers agree that more studies are needed to fully understand their effects on human health.¹³

What can you do?

It seems unlikely that the US government will impose restrictions on use of neonics in the near future. Following are some suggestions of what we can do as consumers and as stewards of our
own yards and gardens.

• Buy organic fruits and vegetables when available and affordable.
• Buy vegetable plants, fruit trees, and ornamental plants that are organic or, at a minimum, free of neonicotinoids and other systemic pesticides. The New Hope Bird Alliance lists nurseries and retail stores that offer organic ornamental plants. See the link below.
• When shopping retail, ask if plants are treated with neonicotinoids. If they don’t know, don’t purchase the plant. If businesses receive multiple inquiries about neonics, especially if customers are walking out of the store, they may rethink buying from suppliers who do not grow plants free of systemic insecticides.
• Purchase seeds from organic sources. Three sources in NC include Sow True Seeds, Ernst Seeds, and Garrett Wildflower Seed.
• Avoid treating your garden with neonic products. The Center for Food Safety published a list at the link below of products produced with neonicotinoids.
• Never use pet collars that contain neonics, which may pose a risk to both children and pets.
• Contact your local legislators and urge the introduction of bills that limit neonicotinoid use.

(Image credit: NCSU Cooperative Extension.)

Notes:

1. K. Rosenberg, A. Dokter, et al.(2019) “Decline of the North American avifauna” Science Vol 366, Issue 6461, pp. 120-124.
2. John Fitzpatrick, Cornell Ornithology Lab; Peter Marra, Georgetown Environmental Initiative (2019) “A Crisis for Birds is a Crisis for Us All”, New York Times commentary.
3. Francisco Sanchez-Bayo, Kris A. G. Wyckhuys. (2019) “Worldwide decline of the entomofauna: A review of its drivers”. Biological Conservation, Volume 232, pp 8-27.
4. S.D. Frank and J. F. Tooker. (2020) “Neonicotinoids pose undocumented threats to food webs” Proceedings of National Academy of Sciences, 117 (37) 22609-22613.
5. Pierre Mineau, Senior Research Scientist at Environment Canada; Cynthia Palmer, senior editor, Environmental Health News (2013) “The Impact of the Nation’s Most Widely Used Insecticides on Birds” American Bird Conservancy pdf.
6. A. Lentola, A. David, et al. (2017) “Ornamental plants on sale to the public are a significant source of pesticide residues with implications for the health of pollinating insects”, Environmental Pollution Volume 304 pp. 297-304.
7. Christopher A. Halsch, L. Forister, Sarah M. Hoyle, et al. (2023) “Milkweed plants bought at nurseries may expose monarch caterpillars to harmful pesticide residues” Biological Conservation, Volume 273.
8. Nanda, A. Ganguly, M. Mandi, et al. (2024) “Neonicotinoid Contamination in the Aquatic Ecosystems—What We Know?” Springer Nature in Sustainable Landscape Planning and Natural Resources Management pp. 29-42.
9. bayer-neonicotinoids-report-2025-4-15-final.pdf.
10. Chi-Hsuan Chang,† David MacIntosh,† Bernardo Lemos, et al. (2018) “Characterization of Daily Dietary Intake and the Health Risk of Neonicotinoid Insecticides for the U.S. Population” J. Agricultural Chemistry Volume 66 , pp.10097-10105.
11. A. Cimino, A. Boyles, K. Thayer, M. Perry (2016) “Effects of Neonicotinoid Pesticide Exposure
    on Human Health: A Systematic Review” Environmental Health Perspectives Volume 125 pp.155-162.
12. Duo Zhang,  Shaoyou Lu (2022) “Human Exposure to Neonicotinoids and the Associated Health Risks: A Review” Environment International Volume 163 107131.
13. Personal Communication, Julie Daniels, PhD. September, 2025.
14. Darrin A. Thompson, Hans-Joachim Lehmler, et al. (2020) “A critical review on the potential impacts of neonicotinoid insecticide use: current knowledge of environmental fate, toxicity, and implications for human health” Environmental Science Process Impacts, Volume 22 Issue 6, pp 1315–1346.

Additional Reading and Resources

The Center for Food Safety provides a list of insecticides that contain neonics which affect bees and other pollinators. https://www.beyondpesticides.org/assets/media/documents/pollinators/documents/pesticide_list_final.pdf

The New Hope Bird Alliance lists sources for purchasing organic plants. https://newhopebirdalliance.org/bird-friendly-certification/native-plants/

Read about how the use of neonics caused the devastation of a lush, pollinator paradise in North Carolina: Restoring Eden: Unearthing the Agribusiness Secret That Poisoned My Farming Community, Elizabeth Hilborn, Chicago Review Press, 2023.

Short Link: https://wp.me/p2nIr1-6C0

Edited by Martha Keehner Engelke