Monarch Butterfly (Danaus plexippus) Life-Stage Risks from Foliar and Seed-Treatment Insecticides
Krishnan N, Zhang Y, Aust ME and others. Environmental toxicology and chemistry, May 2021.
Go to the paper May need a subscription · doi:10.1002/etc.5016
What this paper is about
Restoring monarch habitat in the corn and soybean landscape means putting milkweed next to fields that get sprayed. This study measured the toxicity of the insecticides actually used there.
It covers eggs, larvae and adults, by diet and by direct contact, so the risk can be assessed for each stage rather than for the species as a whole.
Summarised here from the abstract below. Not the authors’ words.
Abstract
Conservation of North America's eastern monarch butterfly (Danaus plexippus) population would require establishment of milkweed (Asclepias spp.) and nectar plants in the agricultural landscapes of the north central United States. A variety of seed-treatment and foliar insecticides are used to manage early- and late-season pests in these landscapes. Thus, there is a need to assess risks of these insecticides to monarch butterfly life stages to inform habitat conservation practices. Chronic and acute dietary toxicity studies were undertaken with larvae and adults, and acute topical bioassays were conducted with eggs, pupae, and adults using 6 representative insecticides: beta-cyfluthrin (pyrethroid), chlorantraniliprole (anthranilic diamide), chlorpyrifos (organophosphate), imidacloprid, clothianidin, and thiamethoxam (neonicotinoids). Chronic dietary median lethal concentration values for monarch larvae ranged from 1.6 × 10-3 (chlorantraniliprole) to 5.3 (chlorpyrifos) μg/g milkweed leaf, with the neonicotinoids producing high rates of arrested pupal ecdysis. Chlorantraniliprole and beta-cyfluthrin were generally the most toxic insecticides to all life stages, and thiamethoxam and chlorpyrifos were generally the least toxic. The toxicity results were compared to insecticide exposure estimates derived from a spray drift model and/or milkweed residue data reported in the literature. Aerial applications of foliar insecticides are expected to cause high downwind mortality in larvae and eggs, with lower mortality predicted for adults and pupae. Neonicotinoid seed treatments are expected to cause little to no downslope mortality and/or sublethal effects in larvae and adults. Given the vagile behavior of nonmigratory monarchs, considering these results within a landscape-scale context suggests that adult recruitment will not be negatively impacted if new habitat is established in close proximity of maize and soybean fields in the agricultural landscapes of the north central United States. Environ Toxicol Chem 2021;40:1761-1777. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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Milkweed USA. (2026). Monarch Butterfly (Danaus plexippus) Life-Stage Risks from Foliar and Seed-Treatment Insecticides (listing). Retrieved DATE, from https://milkweedusa.com/research/monarch-butterfly-danaus-plexippus-life-stage-risks-from-foliar-2021/
"Monarch Butterfly (Danaus plexippus) Life-Stage Risks from Foliar and Seed-Treatment Insecticides (listing)." Milkweed USA, 2026, https://milkweedusa.com/research/monarch-butterfly-danaus-plexippus-life-stage-risks-from-foliar-2021/. Accessed DATE.
Milkweed USA. "Monarch Butterfly (Danaus plexippus) Life-Stage Risks from Foliar and Seed-Treatment Insecticides (listing)." Last modified 2026-08-01. Accessed DATE. https://milkweedusa.com/research/monarch-butterfly-danaus-plexippus-life-stage-risks-from-foliar-2021/.
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title = {Monarch Butterfly (Danaus plexippus) Life-Stage Risks from Foliar and Seed-Treatment Insecticides (listing)},
author = {{Milkweed USA}},
year = {2026},
url = {https://milkweedusa.com/research/monarch-butterfly-danaus-plexippus-life-stage-risks-from-foliar-2021/},
note = {Accessed DATE}
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