Pesticide-treated seeds harm earthworms, study finds

By Shannon Kelleher

Commonly used pesticides pose a toxic threat to earthworms, creatures considered crucial for the health of soil used to grow crops, according to a new study published Wednesday.

The study builds on evidence that a class of insecticides called neonicotinoids, or neonics, are harming a range of species important for planetary health. Neonics  have been banned in many countries but are popular with farmers in the United States.

The authors of the new study said they found that when earthworms were exposed to four different types of neonics, as well as the fungicide difenoconazole, they suffered damage to their mitochondrial DNA and gained significantly less weight than earthworms not exposed to the chemicals. The pesticides were especially damaging when the worms were exposed to a neonic plus the fungicide in combination.

The findings were published in the journal Environmental Science & Technology Letters.

“We need to re-evaluate the toxicity of neonics and the synergistic effects of neonics and systemic pesticides in those non-target organisms when they are applied to soil simultaneously,” said Chensheng (Alex) Lu, a professor at Southwest University in Chongqing, China and an author of the study.

“The contribution of earthworms to crop yields is as essential as pollination done by honey bees,” he added. “A healthy soil is simply not possible without the presence of earthworms.”