Presentation delivered by C.Bahlai at Entomological Society of America Meeting Nov 16, 2014, Portland, Oregon

1. Dual regime shifts in dynamics of an
invasive predator
are linked to the invasion and insecticidal
control of its prey
Christine A. Bahlai1, Wopke vander
Werf2, Matthew O’Neal3, Lia
Hemerik2, Douglas A. Landis1
1 Michigan State University
2 Wageningen University
3 Iowa State University

2. Regime shifts
 Substantial, persistent changes in function of an
ecosystem function or process
 Example: Zebra muscles in Great Lakes drive
dramatic shifts phytoplankton communities
 Dynamics of prey can dramatically
shift the population dynamics in
predatory species
USGS
Scheffer, M., S. Carpenter, J. A. Foley, C. Folke, and B. Walker. 2001. Catastrophic shifts in ecosystems. Nature 413:591-
596.
Strayer, D. L. 2008. Twenty years of zebra mussels: lessons from the mollusk that made headlines. Frontiers in Ecology and
the Environment 7:135-141.

3. Population regulation in Harmonia
Knapp, A. K., et al. 2012. Past, present, and future roles of long-term experiments in the LTER Network. Bioscience 62:377-
389.

4. Model selection
 Fit Ricker model to population
time series
 Allow K and r to vary
 Use AIC to determine best fit
Population this year
푵 풕 + ퟏ = 푵 풕 풆풙풑 풓 ퟏ −
푵 풕
푲
Population next year
Per capita rate of increase
Bruce E. Kendall, W. M. Schaffer, C. W. Tidd,
and Lars F. Olsen. The Impact of Chaos on
Science and Society (UNU; 1997; 394 pages)
Carrying capacity

5. 1996
1995
0.6
0.4
1994
2001
1997
1998
2000
1999
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
0.2
0.0 0.2 0.4 0.6
N(t)
N(t+1)
phase
A
B
C

6. Harmonia dynamics
0.6
0.4
0.2
0.0
1995 2000 2005 2010
Year
Average captures per trap
phase
A
B
C
Same r and
K?
 Arrival of soybean aphid (2000) induced shift in Harmonia’s
dynamic regime
 r +20%, K +40%
 What caused return to previous regime after 2005?

7. Soybean aphid
State
2000
2001
2002
2003
2004
2005
2006
2007
2008
No more major
outbreaks in MI
2009
2010
2011
2012
Michigan
Iowa
Illinois
Wisconsi
n
Low Spotty Moderate High
No aphids Widespread outbreaks

8. Pesticide use
0.004
0.003
0.002
0.001
0.000
Cyhalothrin-lambda
2000 2004 2008
0.003
0.002
0.001
0.000
Esfenvalerate
2000 2004 2008
0.020
0.015
0.010
0.005
0.000
Imidacloprid
2000 2004 2008
0.015
0.010
0.005
0.000
Thiamethoxam
2000 2004 2008
State
Year
kg active ingredient per hectare
2008
2008
2008
Stone, W. W. 2013. Estimated Annual
Agricultural Pesticide Use for Counties of
the Conterminous United States, 1992–
2009. U.S. Geological Survey Data Series
752:http://pubs.usgs.gov/ds/752/.
2008
State
IA
IL
MI
WI
Foliar Seed applied

9. Seed treatments and soybean aphid
 Seed treatments: limited window of efficacy
(~40DAP)
0 DAP 40 DAP
 Early season suppression leads to regional control?
Aphid populations
Time
EIL
Johnson, K. D., M. E. O'Neal, D. W. Ragsdale, C. D. Difonzo, S. M. Swinton, P. M. Dixon, B. D. Potter, E. W. Hodgson, and A.
C. Costamagna. 2009. Probability of cost-effective management of soybean aphid (Hemiptera: Aphididae) in North America.
Journal of Economic Entomology 102:2101-2108.

10. Aphid infestation vs pesticide use
0.004
0.003
0.002
0.001
Cyhalothrin-lambda
Low Spotty Moderate High
0.0025
0.0020
0.0015
0.0010
0.0005
0.0000
Esfenvalerate
Low SpottyModerate High
0.020
0.015
0.010
0.005
0.000
Imidacloprid
Low Spotty Moderate High
0.010
0.005
0.000
Thiamethoxam
Low SpottyModerate High
Aphid infestation
kg active ingredient per hectare

11. Conclusions
 Soybean aphid is less abundant at a regional scale
since the introduction of neonicotinoid seed treatments
 Harmonia dynamics are indistinguishable from their
dynamics before soybean aphid’s arrival.
 Agricultural management has driven a regime shift

12. Implications
 Neonicotinoid regulation-a
changing landscape?
 Can we maintain
landscape-level
suppression of two
invasives?
 Resistant soybean Rag
genes- season long
suppression
Myers, C. and E. Hill. 2014. Benefits of neonicotinoid seed treatments to
soybean production. United States Environmental Protection Agency.
http://www2.epa.gov/pollinator-protection/benefits-neonicotinoid-seed-treatments-
soybean-production.
Hallmann, C. A. et al . 2014. Declines in insectivorous birds are associated
with high neonicotinoid concentrations. Nature advance online
publication.
Blacquière, T., G. Smagghe, C. M. van Gestel, and V. Mommaerts. 2012.
Neonicotinoids in bees: a review on concentrations, side-effects and risk
assessment. Ecotoxicology 21:973-992.

13. Metadata
 @cbahlai
https://github.com/cbahlai/LTER_Ladybeetle_Ricke
r
 Data sources:
 Cooperative Extension (MSU, ISU, UI, UW- aphid
scouting data)
 Doug Landis, Stuart Gage, Manuel Colunga-Garcia
(MSU-ladybeetle data)
 Wesley Stone (USGS- Pesticide data)
 USDA-NASS (Crop production data)

14. Acknowledgements
 Data creators
 J. Megan Woltz and Julia Perrone
 Funding agencies