Solving the RIDL of
Sustainable Bt Corn Use:
Stepping Off the
Biotechnology Treadmill
Trends in Corn IPM Research:
NCB ESA Symposium
Paul D. Mitchell and Zhe Dun
Ag & Applied Economics, UW-Madison
March 14, 2011 Minneapolis, MN
Overview
 Benefits and impacts of Bt corn
 Biotechnology Treadmill, IRM and the need
for resistance mitigation research
 Genetic Pest Management
 Release of Insects carrying a Dominant
Lethal (RIDL)
 Preliminary exploratory model results
Source: Hutchison et al. (2010)
% Acres Triple Stack Bt Corn in 2009
(Based on Biotech Endorsement Crop Insurance)
> 40%
30%-40%
20-30%
10%-20%
< 10%
Source: http://www.ers.usda.gov/briefing/biotechnology/chapter1.htm
Bt Corn Adoption Rate by State
80%
70%
Bt Corn Adoption Rate
60%
IL
MN
WI
IA
NE
50%
40%
30%
20%
10%
0%
1995
1997
1999
2001
2003
2005
2007
2009
ECB Population Data 1940 to 2009
450
WI
IL
MN
2nd Genr. ECB larvae/100 plants
400
350
300
250
200
150
100
50
0
1940
1950
1960
1970
1980
1990
2000
2010
ECB Population Data Since 1990
450
WI
IL
MN
2nd Genr. ECB larvae/100 plants
400
350
300
250
200
150
100
50
0
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
2010
Bt Corn in the USA
 $2.5 billion cumulative Bt corn benefit for Bt acres in
MN, WI, IL, IA & NE since 1996
 $1.7 billion cumulative Bt corn tech fees paid for Bt
corn in MN, WI, IL, IA & NE since 1996
 Widespread planting of Bt corn has suppressed the
European corn borer (Ostrinia nubilalis: ECB)
population in Midwest


$4.3 billion cumulative Bt corn benefit for non-Bt acres in
MN, WI, IL, IA & NE since 1996
63% of Bt benefit to farmers went to non-Bt acres due to
ECB suppression
 $920 million annual average for farmers (2007-2009),
rising to $1.05 billion once include tech fees
Cumulative Benefits MN, WI, IL
4,000
Cumulative Benefit ($ Million)
3,500
Bt
non-Bt
Total
3,000
2,500
2,000
1,500
1,000
500
0
1995
1997
1999
2001
2003
2005
2007
2009
With Tech Fee, Total Cumulative Benefit about
$8.5 Billion in MN, WI, IL, IA, and NE, with Bt
and Non-Bt Each about Half
9,000
Cumulative Benefits ($ Million)
8,000
7,000
Non-Bt
Bt + Tech
Total
6,000
5,000
4,000
3,000
2,000
1,000
0
1995
1997
1999
2001
2003
2005
2007
2009
Price Effects of Bt corn
 Bt corn has increased corn supply and so reduced
market price of corn:
 10-25% lower corn prices due to Bt corn
 With a base price $7/bu, means $0.50 to $1.40/bu
 Higher corn prices
%DQ Elasticity %DP
DP
means more corn
3%
-0.40
-7.5% -0.53
acres (less CRP,
3%
-0.33
-9.1% -0.64
pasture and cereals)
3%
-0.25
-12.0% -0.84  Working on broader
model for more
5%
-0.40
-12.5% -0.88
definitive estimate of
5%
-0.33
-15.2% -1.06
price effects
5%
-0.25
-20.0% -1.40
Main Point
 Bt corn is popular
 Bt corn is valuable





Bt corn farmers
Seed/Biotech companies
Non-Bt corn farmers
Consumers
Environment
 Losing Bt corn more costly than many realize
“Biotechnology Treadmill” and Insect
Resistance Management
 High-dose/Refuge strategy for delaying
insect resistance to Bt crops

Successful? Compare Bt crops to RR crops
 Recent changes to lower refuge amounts,
seed mixtures and pyramided traits

Has IRM become riskier? Onstad et al. (2011)
 Can only avert the inevitable for so long
 IRM goal has always been to delay
resistance, not to prevent resistance
 IRM only slows speed of the biotechnology
treadmill – it does not stop the treadmill
Insect Resistance to Bt Toxin
 Populations with confirmed field resistance
to Bt toxin in a Bt crop
1.
2.
3.
4.
Fall Armyworm (Spodoptera frugiperda) in
Puerto Rico to Cry1F in Bt corn
Stem Borer (Busseola fusca) in South Africa
to Cry1Ab I Bt corn
Cotton Bollworm (Helicoverpa zea) in AR/MS
to Cry1Ac in Bt cotton
Cotton Bollworm (Helicoverpa armigera) in
China to Cry1Ac in Bt cotton
 More in lab and others in non-GM uses
Resistance Mitigation
 Product Registration in US requires remedial
action plans once field resistance confirmed
 Use of alternative modes (chemical, cultural)
that year and in subsequent years
 End sales of product in the area

Used in Puerto Rico for FAW
 Develop “Case-Specific” Mitigation Action Plan

Really no details except “potentially including
layering of technologies”
Trends in Corn IPM Research:
Resistance Mitigation Research
 Little research on Resistance Mitigation for
chemical insecticides or for Bt crops



Most practices and plans rely on mixing and/or
rotating modes of action and use of synergists
Goal is to reduce survival of resistant insects
Doesn’t stop the treadmill, just slows it down
 More research now is a good idea, to get ready
for problems with Bt crops (and other MOA)


Cost to register new pesticides quite high and
growing, harder to find new modes of action
Larry Buschman’s presentation: Oviposition
deterrence
Trends in Corn IPM Research:
Resistance Mitigation Research
 Which strategies are most effective for
mitigating resistance under what conditions?
 Which strategies are most economical for
mitigating resistance under what conditions?
 Are there new strategies that we can use?
 Is it possible to stop the “biotechnology
treadmill” and have sustainable Bt use?
 Start addressing these questions, before we
lose some valuable Bt crop technologies
Trends in Corn IPM Research:
Genetic Pest Management (Gould 2008)
 Sterile Insect Technique (SIT): beginning of
genetic methods for managing pests


Irradiate males so progeny die as eggs, then
release enough to swamp native male
population
SIT successes: screw worm, Medfly, etc.
 More sophisticated methods explored
theoretically & implemented on small scales



Vanderplank and tsetse fly in Tanzania
Several explore “underdominance” systems
No practical applications of these to SIT
Trends in Corn IPM Research:
Genetic Pest Management (Gould 2008)
 Molecular biology developed new methods:
 Medea Element: ZZmale x ZMfemale normally
gives pM = 25% allele frequency, but with
Medea Element, only ZM survive, so pM ≈ 50%
 Link to other genes to drive useful alleles to
higher frequencies in population:



Focus on insect-vectored diseases: drive
refractory gene into insect population
Reduce fitness of pest populations
Why not Bt susceptibility?
Trends in Corn IPM Research: RIDL
Release of Insects carrying a Dominant Lethal
 Series of papers associated with Luke Alphey
starting in 2000 in Science
 RIDL: release homozygous dominant lethal
(LL) into population of wild types (ww)
 RIDLmales(LL) x Wildfemale(ww)



F1: all Lw so 100% F1 females die
F2: Lw x ww so 50% F2 females die
F3: Lw x ww so 50% F3 females die
RIDL Graphics (Alphey et al. 2007)
F2: Lw x ww
50% Lw, all
females die
F1
Figure 1 in Alphey et al. (2007)
50% ww, all
females live
F3: Same
outcome
Trends in Corn IPM Research: RIDL
 SIT: release males causing fatality of
progeny, but does not introgress useful genes
 RIDL: Use L alone to manage population, but
with smaller release rates than SIT
 Alternative: Link desired allele(s) to the L
allele and introgress useful genes
 Insect vectored disease refractory genes

Oxitec (Alphey) transgenic mosquito releases
in Caribbean in Sept 2009 for Dengue Fever
 Bt toxin susceptibility: JEE 2007, 2009
RIDL for Sustainable Bt Corn Use
(Alphey et al. 2007, 2009)
 Theoretically, use RIDL to get any desired
resistance allele frequency and population
 Choose refuge % and RIDL release ratio,
based on pest ecology, population dynamics,
and genetic parameters
 Can step off the “Biotechnology Treadmill”
 No economics in the analysis
Preliminary Exploratory Model
 Building Alphey et al. model to replicate
results and then do new work
 Basic model working




Bt and non-Bt patches, random mating,
relative fitness, dominance, etc.
Start at 10% resistance allele frequency (i.e.,
field resistance observed)
Only releasing ss adults, not LLss adults
Not true RIDL yet, just mass release
 “Mass Released Refuge”
0% refuge
10% refuge
Preliminary Economic Analysis
 Revenue minus costs from Bt and non-Bt
crop and for releasing RIDL insects
 Revenue = PY[b(1 – lb) + (1 – b)(1 – ln)]
 Cost = K + bT + Cridl(dN)
 P = price, Y = pest free yield, b = % Bt
 l = % yield loss, Subscript b for Bt, n for non
Bt, depends on pest population on each
 K = cost, T = tech fee
 Cd(dN) = cost per RIDL insect (convex)
Preliminary Results
 Conceptually, can use mass release for sustainable
management of pest population and resistance
 Pulsed release of ss/RIDL insects




Initially knock down resistance, then use RIDL to
manage population
Threshold (when) and how many to release depend on
biological and economic parameters
Lower optimal release ratio than for SIT
Pulsing comparable to Onstad’s presentation idea of
using Bt corn every 2 or 3 years instead of continuously
 Many practical and technical issues to address
Some of the Questions to Address
 What is the cost to raise enough ECB or
CRW for mass release?
 What is cost to engineer RIDL ECB/CRW?
 How do we mass release ECB/CRW?
Aerially? On the ground? Spacing?
 What are the legal, social, ethical issues for
releasing ss CRW/ECB? What about
transgenic RIDL adults?
 Is RIDL more economical for managing
resistance mitigation?
Questions and Comments
Paul D. Mitchell
UW-Madison Ag & Applied Economics
Office: (608) 265-6514
Cell: (608) 320-1162
Email: pdmitchell@wisc.edu
References
 Gould, F. 2008. Broadening the application of




evolutionarily based genetic pest management.
Evolution 62(2):500-510.
Alphey et al. 2007. Managing Insecticide Resistance
by Mass Release of Engineered Insects. J. Econ.
Entomol. 100(5):1642-1649.
Alphey et al. 2009. Combining Pest Control and
Resistance Management: Synergy of Engineered
Insects With Bt Crops. J. Econ. Entomol. 102(2):717732.
Thomas et al. 2000. Insect population control using a
dominant repressible lethal genetic system. Science
287:2474-2476.
GM Mosquito Trial Alarms Opponents, Strains Ties in
Gates-Funded Project. Science 330:1030-1031.