No hatches to match? What’s up with

Neonics?

“I remember there used to be huge fly hatches on my favorite trout stream,
but over the years there has been a noticeable decrease.”

You’ve probably heard something like this or told someone yourself- but it isn’t just in your head- a decrease in insects has been documented across the globe. In fact, the three major insect groups that fly anglers cherish – caddisflies, mayflies, and stoneflies – have already lost many species. Studies in the Midwest of have shown a 50-80% decrease in mayfly populations. Aquatic insects are key food sources for fish, and they also help to keep water bodies healthy by decomposing leaf matter, filtering water, and controlling erosion.

The causes of the aquatic insect decline are intertwined. They include habitat loss to agriculture, pollution, pesticides impacts, invasive species, disease, and climate change. However, research tells us that the 60 plus years of widespread and sometimes unwarranted use of pesticides in agriculture has caused most of the decline in aquatic insects. The use of synthetic pesticides, such as neonicotinoids, has been a major driver in recent years. Neonicotinoids (KNEE-oh-NICK-uh-tin-oids), or “neonics” (KNEE-oh-nicks) are the most used insecticides nationwide and likely the most ecologically harmful pesticides since DDT.

We’re worried about neonics- you should be too.

Neonics decimate aquatic ecosystems. Neonics are highly toxic to aquatic invertebrates that form the base of aquatic food webs. Introduction of neonics in Japan caused the collapse of a fishery within a year, and similar neonic levels are being detected in U.S. waters.

Neonics are pervasive. Neonics are “systemic,” meaning they are water soluble, and long lasting.  This allows them  to rapidly contaminate surface and groundwater and stick around for up to three years. Recent research in Minnesota showed neonics in 97% of water samples from rivers and streams, and 74% of groundwater samples, including at levels above the tolerance level of aquatic insects.

The majority of Neonic use is unregulated. Neonics are used to coat seeds.  Although neonics are regulated as a pesticide, a legal loophole means treated seeds are not regulated.  Most of the corn and soybean seeds sold in Minnesota are treated with neonics but escape regulation because of this loophole. When neonics are applied to seeds, they can be absorbed by the plant as it grows, providing systemic protection against pests. However, not all the neonics applied to seeds are taken up by the plant, in fact studies show that less than 10% generally is, leaving over 90% to remain on the surface of the seeds or in the surrounding soil. When it rains or when irrigation water is applied, these surface residues can be washed off the treated seeds and into the soil or nearby water bodies.

Neonics make no economic sense. Neonic treated seeds have not been shown to offer any economic benefit to farmers compared to untreated seeds. The increased cost of treated seeds is less than any marginal increase yield. Additionally, use of neonic on lawns and gardens is unnecessary. In contrast, trout fishing is an economic boon to southeast Minnesota and contributes nearly 1 billion dollars per year to the State’s economy.

What’s next?

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Want to Learn More?

Beketov, M. A., Kefford, B. J., Schafer, R. B., & Liess, M. (2013). Pesticides reduce regional biodiversity of stream invertebrates. Proceedings of the National Academy of Sciences, 110(27), 11039–11043. https://doi.org/10.1073/pnas.1305618110

Berens, M. J., Capel, P. D., & Arnold, W. A. (2021). Neonicotinoid Insecticides in Surface Water, Groundwater, and Wastewater Across Land‐Use Gradients and Potential Effects. Environmental Toxicology and Chemistry, 40(4), 1017–1033. https://doi.org/10.1002/etc.4959

Main, D. (2019, November 13). How the world’s most widely used insecticide led to a fishery collapse. Animals. https://www.nationalgeographic.com/animals/article/neonicotinoid-insecticides-cause-fish-declines-japan

Sánchez-Bayo, F., & Wyckhuys, K. A. G. (2019). Worldwide Decline of the entomofauna: a Review of Its Drivers. Biological Conservation, 232(232), 8–27. https://doi.org/10.1016/j.biocon.2019.01.020

Insecticide Seed Treatments Threaten Midwestern Waterways | Xerces Society. (n.d.). Www.xerces.org. Retrieved March 4, 2024, from https://www.xerces.org/publications/fact-sheets/insecticide-seed-treatments-threaten-midwestern-waterways

Is Your Food Killing Your Fishing? – Trout Unlimited. (2022, March 7). Www.tu.org. https://www.tu.org/magazine/conservation/stephenson-bugs/‌

Tell the EPA: Overuse of Pesticide-Treated Seed is a Threat to Waterways and Wildlife. (n.d.). Xerces Society. Retrieved March 5, 2024, from https://www.xerces.org/blog/EPA-comments-treated-seed