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Impact of Permethrin Mosquito Control on Monarch Butterfly Larvae Survival

This study investigates the lethal effects of permethrin, a commonly used mosquito adulticide, on monarch butterfly larvae (Danaus plexippus). Conducted in 2003-2004, it assesses the mortality rates in larvae fed milkweed (Asclepias) treated with permethrin. The research examines variables such as timing of exposure to treated leaves and larval development stages. Results indicate that exposure to recently treated milkweed increases mortality and that larvae exposed to sublethal concentrations may experience slower development and reduced adult mass. Further studies are needed on the implications of adulticides for non-target insects.

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Impact of Permethrin Mosquito Control on Monarch Butterfly Larvae Survival

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  1. The Effects of Mosquito-Control Applications of Permethrin on Monarch Butterfly (Danaus plexippus) Larvae By Sara Brinda 2003-2004 http://www.hwcn.org/link/hmm/mbcat.JPG

  2. Background • Permethrin (Mosquito spray) • Pyrethroid pesticide • Sprayed in ULV form as mosquito adulticide • Applied to wooded areas, where milkweed can grow

  3. Background • Monarchs: non-target insect • Larvae (caterpillars) are terrestrial • Only eat milkweed (Asclepias) http://www.mbsf.org/news.html

  4. Background • Little research conducted on effect on non-target invertebrates • Only peer-reviewed field study (Jensen et al): immediate mortality in aquatic and night-flying insects

  5. Materials and Methods: Part I • Common milkweed (A. syriaca) collected from permethrin-treated areas • Larvae fed with treated milkweed leaves • Three variables • Days between spraying and initial exposure • Days spent on treated leaf • Beginning instar

  6. Hypotheses (Part I) • Milkweed collected from permethrin-treated areas will have lethal effect on monarch larvae • Larval mortality rates will be higher: • Leaves treated more recently with permethrin • Exposed to treated leaves for greater period of time • Exposed to milkweed during earlier instars (growth stages)

  7. Results (Part I): Overall larval mortality

  8. Results (Part I): Variables affecting mortality

  9. Materials and Methods: Part II • Leaves treated in lab with oil solution, 0.1% solution, or 0.5% solution • Leaves fed to monarchs for entire lifetime • Larval mass and instar monitored daily • Adult mass recorded

  10. Hypotheses (Part II) • Larvae exposed to sublethal solution will be affected: • Slower development time • Smaller adult mass • Oil diluent will have no effect

  11. Results (Part II): Total development time

  12. Results (Part II): Adult mass

  13. Further Study • Permethrin effectiveness on mosquitoes vs. nontargets • How effective • Effective for how long? • More research needed on mosquito adulticide effects on non-target insects

  14. Acknowledgements • Dr. Karen Oberhauser • Everyone who worked in the lab this summer • Metropolitan Mosquito Control District, especially Dr. Stephen Manwieler • Ms. Lois Fruen • Team Research • Beth Brinda

  15. The Effects of Mosquito-Control Applications of Permethrin on Monarch Butterfly (Danaus plexippus) Larvae http://www.hwcn.org/link/hmm/mbcat.JPG By Sara Brinda 2003-2004

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