The Effects of Mosquito-Control Applications of Permethrin on Monarch Butterfly (Danaus plexippus) Larvae By Sara Brinda

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

Background Monarchs: non-target insect Larvae (caterpillars) are terrestrial Only eat milkweed (Asclepias)

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

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

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)

Results (Part I): Overall larval mortality

Results (Part I): Variables affecting mortality

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

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

Results (Part II): Total development time

Results (Part II): Adult mass

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

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

The Effects of Mosquito-Control Applications of Permethrin on Monarch Butterfly (Danaus plexippus) Larvae By Sara Brinda