(Beyond Pesticides, April 23, 2020) Pesticide spray drift from adjacent farmlands expose butterfly larvae to lethal pesticide concentrations, according to research published in Environmental Toxicology and Chemistry by Iowa State University (ISU). Lack of previous experimental pesticide toxicity data makes it unclear as to what degree insecticides impact monarch butterfly (Danaus plexippus) productivity in milkweed (Asclepias spp.) habitats near pesticide-treated pasture. This study adds weight to the idea that pesticides are playing a role in the ongoing decline of this iconic butterfly, as researchers find insecticide drift from adjacent fields to be strongly associated with larval mortality. Future monarch butterfly conservation efforts should consider risks stemming from pesticide exposure when developing butterfly rehabilitation efforts, according to advocates. As co-author Niranjana Krishnan (ISU graduate student) states, “In order to make the best decisions about how and where to plant milkweed, we first need to find basic toxicity and exposure data.” ISU researchers established monarch butterfly colonies by collecting larvae from roadside milkweeds, which they then reared in the laboratory for incubation. To analyze the relative toxicity of various insecticides on monarch butterflies, researchers applied normal field-application rates of each pesticide at different larval development stages. Scientists used a bioassay to measure the […]
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