Phillp Pardey, University of Minnesota

1. The Global Occurrence and Economic
Consequences of Stripe Rust in Wheat
Philip Pardey, Yuan Chai, Jason Beddow,
Terry Hurley and Darren Kriticos
University of Minnesota
BGRI 2014 Technical Workshop
Ciudad, Obregon Mexico
March 24, 2014

2. Stem Rust – Global Assessment Summary
Climate suitability
of stem rust
Suitable
Persists

3. 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

4. Implications for Stripe Rust
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?

5. 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

6. Survey Responses—Causes of Expansion in Wheat
Area with Losses Attributed to Stripe Rust
Survey Questions
Aggressiveness
change
Climate change
Susceptible
wheat
Pathogen
adaption
Other
reasons*
Aggressiveness change 15
Climate change 11 13
Susceptible wheat 13 12 16
Pathogen adaption 10 9 10 11
Other reason* 3 4 5 3 5
*Other reasons proposed by survey respondents include cropping system, lack of crop rotation, presence of green
bridge, poor management, and insufficient control strategies.
N = 29 respondents

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

8. Worldwide Stripe Rust Vulnerability (Beta version)
Persistently vulnerable area
Seasonally suitable area
Unaffected area
Area Share Output Share
Suitable Persists Suitable Persists
(Percentage)
North America 41 0.9 46 1.2
Australia 31 8.8 38 12
Sub-Saharan Africa 24 23 19 18
China 84 13 85 11
India 2.5 1.3 0.9 0.5
World 50 17 58 25

9. Source: Pardey et al. (2013)
Average 2.5% per year
Stochastic Structure of U.S. Losses Attributed to Stem Rust
Average 0.29% per year

10. 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

11. Global Stripe Rust Losses Estimates (Beta version)
Reference
Period
Counterfactual
Loss
Average annual losses
(million metric tons)
Value of the annual losses
(million U.S. $ per year)*
1961-84 none 0.88 $157
1985-99 none 0.34 $61
2000-12 none 4.74 $848
Reference
Period
Counterfactual
Period
Losses Averted
(million metric tons)
Value of the benefits
(million U.S. $ per year)*
1961-84 1985-99 0.62 $111
1985-99 1985-99 0 0
2000-12 1985-99 4.45 $797
* 2010 average US wheat prices
No Loss Counterfactual
Low Loss Counterfactual

12. 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
1961-84 Stochastic Loss Structure
$8.0 million per year, or 4 cents per hectare
2000-12 Stochastic Loss Structure
$27.8 million per year, or 12 cents per hectare
Comparative 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 (Beta estimates)

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

14. Changing Spatial Structure of Losses
•Before 1959: no reported losses attributed to stripe rust
•1959-1984: wheat stripe rust caused significant yield losses in the Pacific North-West (PNW) region
•1985-1999: yield losses were generally low because of the use of resistant cultivars and the
application of effective fungicide (Chen 2005)
•Since 2000: stripe rust epidemics became increasingly important in PNW, south central states and
the central Great Plains, causing severe damage.
0
5
10
15
20
25
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
%
U.S. Wheat Yield Losses: Pacific North West (PNW) vs. Non-PNW
PNW&CA % Loss
Non PNW&CA % Loss

15. Summing Up
 Earlier assessment suggests that around $50 million per year 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
 Beta assessment suggests that around $28 million per year be spent to
alleviate global losses from stripe rust, substantially more than would have
been justified several decades ago
 On-going work is assessing the interplay between the spatial pattern of losses,
the spatial extent of those losses, and the research investment implications of
these more recent changes

16. Thanks