Clothianidin & imidacloprid

Clothianidin and Imidacloprid are the most harmful to monarch butterflies from the sample due to their toxicity as neonicotinoid insecticides, which impair monarch survival and reduce their milkweed food source.

Clothianidin and Imidacloprid are significantly worse for monarch butterflies compared to Chlorpropham based on their classification and known effects:

• Clothianidin and Imidacloprid (neonicotinoids) are highly toxic to monarchs, impacting their reproduction, navigation, and survival even at low doses. They also reduce the availability of milkweed by being systemic, meaning they can be absorbed by plants, including milkweed, the monarch's primary larval food source.

• Chlorpropham is primarily a herbicide, used mostly on potatoes to suppress sprouting. While it could indirectly affect monarchs by reducing the availability of some plants, it is not directly toxic to them like neonicotinoids are. Chlorpropham doesn't have the same systemic toxicity or direct harmful effects on pollinators as Clothianidin and Imidacloprid.

In comparison, Clothianidin and Imidacloprid are much more harmful to monarchs than Chlorpropham, which has only an indirect impact through habitat modification rather than direct toxicity.