A Global Bio-economic Assessment of the Production and Research Implications of Wheat Rusts

Philip Pardey Yuan Chai, Jason Beddow, and Terry Hurley

University of Minnesota

ICW2015

Four Seasons Hotel, Sydney September 22, 2015

What do we Know About Wheat Rust Losses?

“The wheat rusts, historically, have been diseases of great

importance. The losses caused by…the three wheat rusts

worldwide over the centuries have been substantial….

Unfortunately, in many instances, recording and

quantification of the rust diseases and the losses attributed

to them have not been adequate. All too often, references to

their occurrence appear in obscure publications and only

when an epidemic is unusually severe."Roelfs, Singh and Saari (Rust Diseases of Wheat, CIMMYT 1992)

Wheat Rust Bio-Economic Evidence

Stem Rust (Science 2013)

Stripe Rust(Nature Plants 2015)

Leaf Rust(Forthcoming 2015/16?)

Rust and R&DRust and the Red Queen’s Race

"Well, in our country," said Alice, still panting a little, "you'd generally get to somewhere else—if you run very fast for a long time, as we've been doing."

…. said the Queen. "Now, here, you see, it takes all the running you can do, to keep in the same place. If you want to get somewhere else, you must run at least twice as fast as that!“

Lewis Carroll (Through the Looking Glass, 1871)

Ruttan and Rust“If the research effort required to maintain productivity is a positive function of the productivity level, it seems apparent that maintenance research will rise as a share of the research budget…..”

Vernon Ruttan (Agricultural Research Policy, 1982)

Resistance Genes as Biological Capital“Breeding new crop varieties with resistance to the biotic stresses that undermine crop yields is tantamount to increasing the amount and quality of biological capital in agriculture.

However, the success of genes that confer resistance to pests induces a co-evolutionary response that depreciates the biological capital embodied in the crop, as pests evolve the capacity to overcome the crop's new defences.

Thus, simply maintaining this biological capital, and the beneficial production and economic outcomes it bestows, requires continual reinvestment in new crop defences.”

Beddow et al. (Nature Plants, September 2015)

Stem Rust Climate Suitability

Persistently vulnerableSeasonally vulnerable

Stripe Rust Climate Suitability

Persistently vulnerableSeasonally vulnerable

Leaf Rust Climate Suitability

Persistently vulnerableSeasonally vulnerable

Note: Suitability prediction based on growth index (GI) values from the CLIMEX model

Three Rusts—Seasonally Vulnerable

Two rust types

Three rust types

One rust type

Note: Suitability prediction based on the ecological index (EI) values from the CLIMEX model

Three Rusts—Persistently Vulnerable

Two rust types

Three rust types

One rust type

Vulnerability to Wheat Rusts Worldwide

Stem, Leaf and Stripe Rust Vulnerability

None Only One Only Two All Three(Percentage of output, all farms)

Western Europe 0.0 0.0 0.7 99.2

North America 2.2 12.5 37.1 48.3

Australia 0.0 10.3 17.8 71.9

Sub-Saharan Africa 11.0 3.6 13.9 71.6

China 0.0 0.0 11.5 88.5

India 6.3 18.8 72.5 2.5

World 3.2 6.9 27.1 62.7

Estimating Global Losses

Jointly address

Highly variable nature of the losses over time

Spatially variable nature of the losses (across the rusts, production systems, and time)

Spatio-temporal Variation of Stem Rusts

1918-1959

1960-2014

Average annualpercent loss

Spatio-temporal Variation Stripe Rust

1918-1959

1960-2014

Average annualpercent loss

Spatio-temporal Variation of Leaf Rust

1918-1959

1960-2014

Average annualpercent loss

1918

1922

1926

1930

1934

1938

1942

1946

1950

1954

1958

1962

1966

1970

1974

1978

1982

1986

1990

1994

1998

2002

2006

2010

2014

0

5

10

15

20

25 Leaf RustStripe RustStem Rust

Perc

ent L

oss

Characterizing the Temporal Variability of Losses, 1918-2014

21.4%

0.45%

Characterizing the Temporal Variability of Losses

0.00% 5.00% 10.00% 15.00% 20.00% 25.00%0

0.10.20.30.40.50.60.70.80.9

1

Observed FrequencyBeta Distribution

Proportional Losses

Cum

ulati

ve F

requ

ency

Fitted Beta Distribution

Characterizing the Spatial Variability of Losses 1 S 2 Y 3 L

4 SYL

1 S 2 Y

4 SYL

3 L

5 SY

6 YL7 LS

Disjoint

Concordant

Overlapping

World Shares (percent)

No rust 3.2

One rust 6.9

Two rusts 27.1

Three rusts 62.7

Production Loss Consequences of Wheat Rusts

Probability of loss in each epidemiological zone

Magnitude of loss (proportionate terms)

Geographic extent of loss

• Wheat area

• Wheat yields

Factors Affecting Loss Estimates

15.04 Mill. Tons

High Input Area All Area -

2,000,000.00

4,000,000.00

6,000,000.00

8,000,000.00

10,000,000.00

12,000,000.00

14,000,000.00

16,000,000.00

3,911,976.61 4,874,573.89

1,565,063.71 1,869,170.85

6,989,273.63

8,300,559.19

LeafStripeStem

Production Loss Consequences of Wheat RustsAnnual Average Losses, 1961-2050

12.47 Mill. Tons

High Input Area

All Area $-

$20,000,000.00

$40,000,000.00

$60,000,000.00

$80,000,000.00

$100,000,000.00

$120,000,000.00

$28,004,658.3

5

$34,991,655.6

6

$11,203,818.1

4

$13,417,661.5

7

$50,034,097.7

5

$59,584,758.6

9 LeafStripeStem

Global Research Implications of Wheat Rusts

Economically Justifiable Investments 95% chance that investments in wheat rust research will exceed MIRR of 10% per year

$89.24 mill

$107.99 mill

Take Home Messages Almost all of the world’s wheat crop is susceptible to infection from wheat rusts

• Globally only 3.2 percent of the crop is grown in areas not susceptible to infection

• 62.7 percent of the crop is in areas that are vulnerable to all three rusts

Losses at any particular location or point in time are NOT representative of the average annual global losses worldwide over the longer term

Using a Monte Carlo probabilistic approach applied to 15 epidemiological zones with variable vulnerability to the rusts we find that:

• Global losses from all three rusts average at least 15.04 million tons (552.8 million bushels) per year. This is equivalent to an annual average loss of around US$2.9 billion (2010 prices) per year.

• The economically justifiable investment in wheat rust R&D is conservatively estimated to be $108 million per year (effectively in perpetuity!)

o This is equivalent to an annual investment of $0.51 per hectare per year (across the world’s 212.38 million wheat hectares)

Thanks

www.instepp.umn.edu