The Effects of Mosquito-Control The Effects of Mosquito-Control Applications of Permethrin on Monarch Applications of Permethrin on Monarch

Butterfly (Butterfly (Danaus plexippusDanaus plexippus) Larvae) Larvae

By Sara Brinda

2003-2004

http://www.hwcn.org/link/hmm/mbcat.JPG

BackgroundBackground

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

grow

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http://www.mbsf.org/news.html

BackgroundBackground

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

BackgroundBackground

• 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 IMaterials 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

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Hypotheses (Part I)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 Results (Part I): Overall larval mortalitymortality

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1st instar 2nd instar 3rd instar

Beginning instar

Proportion dead

Control

Treated

81

111 153

32

136 21

Results (Part I): Variables Results (Part I): Variables affecting mortalityaffecting mortality

Variable Coefficient Std. error p-value

Beginning instar -0.8220 0.3661 0.0248Days on treated leaf -1.2589 0.3279 0.0001Days since spraying -0.0106 0.0595 0.8578

Materials and Methods: Part IIMaterials 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

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.

Hypotheses (Part II)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 Results (Part II): Total development timedevelopment time

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Beginning instar

Mean development time (days)

Control

Oil

0.1% Solution

0.5% Solution

4 6 6 7 4 5 2 8 9 8

Results (Part II): Adult massResults (Part II): Adult mass

Variable Coefficient Std. Error p-value

Beginning instar -0.0101 0.0314 0.2639Oil 0.0024 0.0089 0.8935

0.1% Solution -0.0242 0.0182 0.19130.5% Solution -0.0864 0.0418 0.0436

Further StudyFurther Study

• Permethrin effectiveness on mosquitoes vs. nontargets– How effective– Effective for how long?

• More research needed on mosquito adulticide effects on non-target insects

AcknowledgementsAcknowledgements

• 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 The Effects of Mosquito-Control Applications of Permethrin on Monarch Applications of Permethrin on Monarch

Butterfly (Butterfly (Danaus plexippusDanaus plexippus) Larvae) Larvae

By Sara Brinda

2003-2004

http://www.hwcn.org/link/hmm/mbcat.JPG