1. 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, Minneapolis, MN

2. 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

3. Source: Hutchison et al. (2010)

4. % Acres Triple Stack Bt Corn in 2009 (Based on Biotech Endorsement Crop Insurance)
> 40%
30%-40%
20-30%
10%-20%
< 10%

5. Source: http://www.ers.usda.gov/briefing/biotechnology/chapter1.htm

6. Bt Corn Adoption Rate by State

7. ECB Population Data 1940 to 2009

8. ECB Population Data Since 1990

9. 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 ( ), rising to $1.05 billion once include tech fees

10. Cumulative Benefits MN, WI, IL

11. With Tech Fee, Total Cumulative Benefit about $8
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

12. 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 means more corn acres (less CRP, pasture and cereals)
Working on broader model for more definitive estimate of price effects
%DQ
Elasticity
%DP DP 3%
-0.40
-7.5%
-0.53
-0.33
-9.1%
-0.64
-0.25
-12.0%
-0.84 5%
-12.5%
-0.88
-15.2%
-1.06
-20.0%
-1.40

13. 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

14. “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

15. Insect Resistance to Bt Toxin
Populations with confirmed field resistance to Bt toxin in a Bt crop
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

16. 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”

17. 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

18. 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

19. 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

20. 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?

21. 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

22. RIDL Graphics (Alphey et al. 2007)
F2: Lw x ww
50% Lw, all females die
50% ww, all females live
F3: Same outcome F1
Figure 1 in Alphey et al. (2007)

23. 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

24. 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

25. 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”

27. 0% refuge

28. 10% refuge

29. 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)

33. 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

34. 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?

35. Questions and Comments
Paul D. Mitchell
UW-Madison Ag & Applied Economics
Office: (608)
Cell: (608)

36. References
Gould, F Broadening the application of evolutionarily based genetic pest management. Evolution 62(2):
Alphey et al Managing Insecticide Resistance by Mass Release of Engineered Insects. J. Econ. Entomol. 100(5):
Alphey et al Combining Pest Control and Resistance Management: Synergy of Engineered Insects With Bt Crops. J. Econ. Entomol. 102(2):
Thomas et al Insect population control using a dominant repressible lethal genetic system. Science 287:
GM Mosquito Trial Alarms Opponents, Strains Ties in Gates-Funded Project. Science 330: