1. The Global Occurrence and Economic
Consequences of Stripe Rust in Wheat
Philip Pardey, Yuan Chai, Jason Beddow,
Terry Hurley, Darren Kriticos and Hans Joachim-Braun
University of Minnesota, CSIRO, and CIMMYT
Second International Wheat Stripe Rust Symposium
Regional Cereal Rust Research Center, Izmir, Turkey
April 28, 2014

2. Stripe Rust: Bio-economic cum Policy Questions
 What is the global extent of this disease?
• Where is it likely to occur and persist?
 What share of global wheat area and production is susceptible to
the disease?
 What is the likely global losses in wheat production associated
with this disease?
 What are the global research investment implications of this
disease?

3. Losses Attributed to Wheat Rust
Will Stem Rust Destroy the World’s Wheat Crop?
“…it is unlikely that stem rust race Ug99 or its descendants will destroy the world’s wheat
crop”
Singh et al. (2008, p.305)
“This *stem rust+ is a time bomb…Ug99 is going to lie there, and then all of the sudden its
going to go boom.”
Quote attributed to Borlaug (Science 2009, p. 721.)
Implied losses in 2009/10 attributed to wheat stem rust: 43.2 to 302.4 MMT
Fisher et al. (Nature 2012, Table s1)
“*Stripe rust+ losses can be severe (50%) due to shriveled grain and damaged tillers. In
extreme situations, stripe rust can cause 100% losses.”
Roelfs et al. (CIMMYT 2002, p.2)

4. Stem Rust – Global Assessment Summary
Climate suitability
of stem rust
Suitable
Persists
Reported Occurrence

5. Source: Pardey et al. (2013) from USDA (various years)
Average 2.5% per year
Stem Rust – Global Assessment Summary
Stochastic Structure of U.S. Losses Attributed to Stem Rust
Average 0.29% per year

6. Stem Rust – Global Assessment Summary
Climate suitability
of stem rust
Suitable
Persists
A sustained investment of $51.1 million
per year (2010 prices) in stem rust
research could be justified economically

7. Historical and Current Stripe Rust Threats
• Historically, stripe rust has mainly been
endemic only in cool climate regions
• In recent decades, stripe rust has spread
rapidly to areas previously unaffected
Before 2000 After 2000
0 Not recorded, or no response
1 Rare
2 Localized in some seasons
3 Localized in most seasons
4 Widespread in some seasons
5 Widespread in most seasons
N = 29

8. U.S. Wheat Yield Losses Attributed to Stripe Rust

9. U.S. Wheat Yield Losses Attributed to Stripe Rust
1960
2012

10. Global Stripe Rust Occurrence

11. Modeling Pests and Diseases- A Spatial Approach

12. CLIMEX Modeled Suitability for Stripe Rust (Beta)
Suitable
Persists

13. Observed and Modeled Occurrence of Stripe Rust

14. Observed and Modeled Occurrence of Stripe Rust

15. Observed and Modeled Occurrence of Stripe Rust

16. Observed and Modeled Occurrence of Stripe Rust

17. Observed and Modeled Occurrence of Stripe Rust
Area Production
Region Suitable Persists Suitable Persists
(percent)
North America 59.9 16.9 63.1 18.6
sub-Saharan Africa 82.6 81.2 83.0 82.0
LAC 85.0 83.0 89.7 88.5
Asia 59.1 32.9 69.4 39.2
FSU 66.2 9.7 78.9 15.7
Australasia 53.3 45.9 55.6 48.0
World 72.0 42.0 79.4 51.2

18. Stochastic Structure of U.S. Losses Attributed to Stripe Rust
The changing structure of stripe rust epidemics
 1961-1984: significant yield losses
 1985-1999: use of resistant cultivars and fungicide
 Since 2000: new stripe rust pathotypes
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5 1961
1964
1967
1970
1973
1976
1979
1982
1985
1988
1991
1994
1997
2000
2003
2006
2009
2012
PercentLoss
Average 0.54% per year
Average 0.15% per year
Average 1.5% per year

19. Global Stripe Rust Losses Estimates
Reference
Period
Counterfactual
Loss
Average annual losses
(million metric tons)
Value of the annual losses
(million U.S. $ per year)*
1961-84 none 1.04 $186
1985-99 none 0.53 $95
2000-12 none 5.77 $1,032
Reference
Period
Counterfactual
Period
Losses Averted
(million metric tons)
Value of the benefits
(million U.S. $ per year)*
1961-84 1985-99 0.74 $132
1985-99 1985-99 0 0
2000-12 1985-99 5.15 $922
* 2010 average US wheat prices
No Loss Counterfactual
Low Loss (1985-1999) Counterfactual

20. Approach
 Estimate of annual investments to avert projected losses (costs) attributable to
stripe rust through to 2048
 Ninety five percent chance of realizing a modified internal rate of return of at
least 10 percent per year
Economically Justified R&D Spending (2010 prices)
 $36.8 million per year, or 17.1 cents per hectare (with a no loss counterfactual)
 $32.9 million per year, or 15.3 cents per hectare (with a low loss counterfactual)
Comparative (Stem rust) Information
• Economically justified investment in stem rust was $51.1 million per year
• U.S. wheat farmers spent $15.75 per hectare on seed
Economically Justifiable R&D Investment

21. Summing Up
 Earlier assessment suggests that around $50 million per year on average be
invested in research to avert prospective global losses from stem rust, double
what is being spent of late
 Evidence suggests a change in the spatial pattern and magnitude of wheat
yield losses attributable to stripe rust
• Around 72 percent of the world’s wheat area is susceptible to this disease
 Beta assessment suggests that around $35 million per year (about two-thirds
the corresponding stem rust research investment) be spent to alleviate global
losses from stripe rust, substantially more than would have been justified
several decades ago

22. Thanks