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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
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BackgroundBackground
• Permethrin (Mosquito spray)– Pyrethroid pesticide– Sprayed in ULV form as mosquito adulticide– Applied to wooded areas, where milkweed can
grow
C
H
3
C
H
3
Cl
Cl
O
O
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http://www.mbsf.org/news.html
BackgroundBackground
• Monarchs: non-target insect• Larvae (caterpillars) are terrestrial• Only eat milkweed (Asclepias)
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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
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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.
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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)
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Results (Part I): Overall larval Results (Part I): Overall larval mortalitymortality
0
0.2
0.4
0.6
0.8
1
1st instar 2nd instar 3rd instar
Beginning instar
Proportion dead
Control
Treated
81
111 153
32
136 21
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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
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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.
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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
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Results (Part II): Total Results (Part II): Total development timedevelopment time
0
5
10
15
20
25
30
35
2nd instar 3rd instar 4th instar
Beginning instar
Mean development time (days)
Control
Oil
0.1% Solution
0.5% Solution
4 6 6 7 4 5 2 8 9 8
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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
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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
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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
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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