According to USDA research published this spring, the neonicotinoid insecticide clothianidin is a likely contributor to monarch butterfly declines in North America. Neonicotinoids are the most widely-used pesticides in the world. Their soluble molecules are capable of making their way into nectar and pollen from soil or seed treatments.
Experiments by USDA researchers showed that clothianidin can impact monarch caterpillar size, weight, and survival at doses as low as 1 part per billion (ppb). The lethal concentration was found to be 15 ppb. Though the caterpillars were exposed to clothianidin-treated food for only 36 hours, the researchers noted that in agricultural environments caterpillar exposure would likely be greater and include other pesticides, including other neonicotinoids. Samples of milkweed plants from corn-growing areas in South Dakota contained on average over 1 ppb clothianidin.
While neonics have been implicated in honey bee decline, the new report is the first to link the pesticides to monarch butterfly survival and reproduction. Cornucopia Farm and Food Policy Analyst Jérôme Rigot, PhD, noted that “although the lethal concentration of 15 ppb is a very low level, the implications are that much lower levels of neonicotinoids, as well as synergistic effects with other pesticides, would significantly and negatively affect caterpillars’ health.”
Neonicotinoid pesticides, which are neurotoxins, are partially banned in the European Union.
This appeared in The Cultivator, News from the Cornucopia Institute, Summer 2015
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