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Neonicotinoids began dominating the agricultural market in the early 2000s, after being referred to as the “perfect” insecticide.

Indeed, the compound made of synthetic nicotine, acts as a neurotoxin on insects and their toxicity allows less active ingredients to be used. Compared with older classes of insecticides, they also appeared to have relatively low toxicity to vertebrates, particularly mammals.

Neonicotinoids are the most used insecticides on the planet and can be sprayed, applied to the soil or used to coat corn, soybean and other crop seeds. They are also found in lawn chemicals and even flea and tick collars for pets.

But they have long been known to be devastating to bees and other pollinators, which led the European Union and some states to ban or heavily restrict their use.

Now, as more and more study is done on them, neonicotinoids are raising alarms about the dangers to much more than pollinator populations.

Minnesota biologists recently announced that the pesticides have been found in 94% of deer spleens collected from road kill and sent in by hunters last fall. And two-thirds of those deer had higher concentrations of the chemicals than a threshold found to potentially lower fawn survival and cause bone and genital deformities in a captive deer study.

A South Dakota researcher found that fawns with higher levels of neonicotinoids in their spleens were much more likely to die than those with lower levels. Similar problems have been found in pheasants.

Other researchers have found that neonicotinoids went from treated plants to pollinators and from plants to pests to natural enemies. The alarming studies show that their transmission through food chains pose a broad risk to biodiversity and food webs.

A recent finalized report from the U.S. Environmental Protection Agency concluded that the three most commonly used neonicotinoids are likely to adversely impact nearly three quarters of species listed as endangered in the United States.

Some farmers are beginning to move away from neonicotinoids, mainly because of their costs versus effectiveness.

While research continues, it is clear that neonicotinoids’ deadly consequences for pollinators and likely problems for a wide variety of other plants and animals means the pesticides’ use needs to be dramatically curtailed.

— Mankato Free Press, Sept. 13