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 MexicoMarch 24, 2014

Stem Rust – Global Assessment Summary

Climate suitabilityof stem rust

Suitable

Persists

Stem Rust – Global Assessment Summary

Climate suitabilityof stem rust

Suitable

Persists

A sustained investment of $51.1 million per year (2010 prices) in stem rust research could be justified economically

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?

Historical and Current Stripe Rust Threats

• Historically, stripe rust has mainly beenendemic only in cool climate regions

• In recent decades, stripe rust has spreadrapidly 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

Survey Responses—Causes of Expansion in Wheat Area with Losses Attributed to Stripe Rust

Survey QuestionsAggressiveness

changeClimate change

Susceptible wheat

Pathogen adaption

Other reasons*

Aggressiveness change 15Climate change 11 13Susceptible wheat 13 12 16Pathogen adaption 10 9 10 11Other 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

U.S. Wheat Yield Losses Attributed to Stripe Rust

Worldwide Stripe Rust Vulnerability (Beta version)

Persistently vulnerable area

Seasonally suitable area

Unaffected area

Area Share Output ShareSuitable Persists Suitable Persists

(Percentage)North America 41 0.9 46 1.2Australia 31 8.8 38 12Sub-Saharan Africa 24 23 19 18China 84 13 85 11India 2.5 1.3 0.9 0.5World 50 17 58 25

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

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

4.519

61

1964

1967

1970

1973

1976

1979

1982

1985

1988

1991

1994

1997

2000

2003

2006

2009

2012

Perc

ent L

oss

Average 0.54% per year

Average 0.15% per year

Average 1.5% per year

Global Stripe Rust Losses Estimates (Beta version)

Reference Period

CounterfactualLoss

Average annual losses(million metric tons)

Value of the annual losses (million U.S. $ per year)*

1961-84 none 0.88 $1571985-99 none 0.34 $612000-12 none 4.74 $848

Reference Period

CounterfactualPeriod

Losses Averted(million metric tons)

Value of the benefits(million U.S. $ per year)*

1961-84 1985-99 0.62 $1111985-99 1985-99 0 02000-12 1985-99 4.45 $797

* 2010 average US wheat prices

No Loss Counterfactual

Low Loss Counterfactual

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)

U.S. Wheat Yield Losses Attributed to Stripe Rust

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 theapplication of effective fungicide (Chen 2005)

•Since 2000: stripe rust epidemics became increasingly important in PNW, south central states andthe central Great Plains, causing severe damage.

0

5

10

15

20

25

1961

1962

1963

1964

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1966

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1968

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1970

1971

1972

1973

1974

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1976

1977

1978

1979

1980

1981

1982

1983

1984

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

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1997

1998

1999

2000

2001

2002

2003

2004

2005

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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

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

Thanks