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) Stripe Rust (Nature Plants 2015) Leaf Rust (Forthcoming 2015/16?) Leaf Rust (Forthcoming 2015/16?)

Rust and R&D Rust 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 vulnerable Seasonally vulnerable

Stripe Rust Climate Suitability Persistently vulnerable Seasonally vulnerable

Leaf Rust Climate Suitability Persistently vulnerable Seasonally 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

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 Average annual percent loss

Spatio-temporal Variation Stripe Rust Average annual percent loss

Spatio-temporal Variation of Leaf Rust Average annual percent loss

Characterizing the Temporal Variability of Losses, % 0.45%

Characterizing the Temporal Variability of Losses Fitted Beta Distribution

Characterizing the Spatial Variability of Losses 1 S2 Y 3 L 4 SYL 1 S 2 Y 4 SYL 3 L 5 SY 6 YL 7 LS Disjoint Concordant Overlapping World Shares (percent) No rust 3.2 One rust 6.9 Two rusts 27.1 Three rusts 62.7 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 Production Loss Consequences of Wheat Rusts Annual Average Losses, Mill. Tons

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 $ 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 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 million wheat hectares)

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