Climate Change and Crop Diseases

1. Climate Change and Crop Diseases RP Thakur ICRISAT, Patancheru, AP, India University of Mysore, 16 Sep 2010

2. Outline • Introduction • Impact on agriculture • Effects on crop diseases & management • Conclusions

3. Introduction • 1896: Svante Arrheinus (Swedish Chemist-Nobel laureate) : role of CO2 in regulating global temp; doubling of CO2 trigger rise of 5-6 C • 2006-07:IPCC 4th report &Al Gore’s “An inconvenient truth”- Oscar award and Nobel prize • 2006- numerous public debate,political discussions and global/regional/national conferences

4. Introduction Some definitions Climate: statistical description for means and variability of key weather parameters for a given area over a period of time – usually 30 years Climate change: any change in climate over time, whether due to natural variability or as a result of human activity Coping strategies: peoples’ long experience in dealing with seasonal variation of weather factors Food system: activities related to production, processing, distribution, preparation and consumption Food security: an operative system that can provide safe and nutritious food to all people, at all times at affordable price for leading active healthy lives

5. Introduction IPCC predictions • Increase in temperature globally • Extreme changes – more frequent higher temp, less frequent lower temp • Increased/decreased intensity of precipitation events in some regions • Changes in storm patterns – influence global movement of pathogens • Icreased precipitation in both summer and winter in high latitude regions • In Asia precipitation will increase in summer

6. Introduction Facts about Global Food Security • World population is 6.8 billion; 9.2 billion by 2050 • 80% live in developing countries, where the population increases 1.9% per year • >800 million people do not have adequate food • 1.3 billion live on less than $1 a day • 50% of poor live in Asia, 25% in Africa, 12% in Latin America in marginal land and fragile ecosystems • Global food production 5 billion tons/yr; required 10 billion tons by 2050

7. Impact on Agriculture Food production under severe threat due to: -higher average temperature - changing rainfall pattern and rising sea levels - more intense extreme events- drought, flood, hurricanes - rise of 2C likely to have severe impact on environment- natural ecosystem-agriculture - change in monsoon rains, melting of glaciers, increased water salinity - all these affect crops and their diseases

8. The cost of climate change By 2050 • 25 million more children malnourished • Wheat yields reduced by 30% and rice yields by 15% in developing countries • Prices increase by 90% for wheat, 35% for maize and 12% for rice • US$7 billion/yr needed to prevent/reduce these impacts Source: IFPRI, 2008

9. Impact on Agriculture • Variable and uncertain weather - the greatest challenges to small-scale farmers and other resource managers • New technologies and knowledge - hardier crops and better ways to manage trees, livestock, water, soil and fish • Need to address both mitigation of and adaptation to climate change.

10. Impact on Crop Production • Wheat production will increase in northern Europe and Canada, while there will be decline in the Indo-Gangetic plain (where 15 %) of the world’s wheat is grown • Wheat production will shrink by more than half by 2050- threat to the food security of 200 million people • Maize production to drop by >15% by 2020 in much of sub-Saharan Africa and in most of India- estimated loss to Africa at $2 billion a year

11. Impact on Crop Production • Countries in the Sahel region of West Africa need to switch to more heat- and drought-tolerant crops, such as sorghum and millet • Rice yields in Bangladesh will decline by more than 20% by 2050 and 50% by 2070 • Temperature rise by 2.3 to 3.8 C and increased rainfall by 2050 will affect: >20% decline in farm income in Andhra Pradesh >30% reduction in sugarcane yield in Maharashtra >12% decline in rice production in Orissa

12. Impact on factors influencing crop production Climate change Farming practices Crop health Crop pest/diseases Development & Deployment of cultivars/transgenics Crop production & Productivity Organic farming Soil health

13. Plant responses to climate change • Lack of adaptation time in altered climate • Change in population genetic structure of plant species • Change in abundance of particular plant species • Certain species may succumb to diseases and pests • Problem in maintaining traditional land races/varieties • Likely loss of biodiversity • Shorter useful life of resistance genes • Need for development of cultivars with wider adaptation

14. Effects on host and pathogens • Changes in plant architecture may affect microclimate and thus risk infection • Increased plant density-increased leaf surface wetness duration- more foliar pathogen infection • Increased frequency of heat and drought may contribute to disease susceptibility/resistance • Elevated CO2 levels - change plant structure- increased leaf area, increased leaf thickness, more number of leaves, higher total leaf area, higher plant biomass- all these would influence infection by pathogens • Elevated O3 can change the leaf surface structure- affecting physical topography and chemical composition, structure of epicuticular wax- may influence pathogen infection- likely enhanced infection by necrotrophic pathogens and root-rot fungi

15. Effect on plant diseases • Alter stages and rates of pathogen development • Modify host resistance • Change the physiology of host-pathogen interactions • Availability and use of chemical pesticides • Specific to pathosystem • Specific to locations

16. Effect on plant diseases • Direct, multiple effects on plant disease epidemiology: survival of primary inoculum, the rate of disease progress during a growing season, and the duration of epidemics • Changes in the spectra of diseases • Increase in abiotic diseases associated with environmental extremes • Interactions between biotic and abiotic diseases more pronounced • Changes in plant disease management strategies • Opportunities for introduction of new crops and cultivars • Need for effective systems to detect new pathogens • Forest trees slow to adapt- new strategy for forest management plans

17. Studies of climate change on plant diseases Climate change studies relate to influence of -temperature, -precipitation, -carbon dioxide, -ozone, -ultraviolet (UV) radiation Greater knowledge required of how these factors affect the physiology of the host plant and the host–pathogen interaction

18. Effect on plant diseases Abiotic factors & host resistance • Drought- lower infection by foliar pathogens • Temperature – influences R-gene expression and vir genes • CO2 can prevent induced resistance • O3 can weaken physical structure and alter chemical composition- increased infection

19. Effects on plant diseases Pathogen-vector responses • Many pathogens have limited range of temperature for overwintering/oversummering • Abrupt changes in temperature range will influence their survival abilities and reproduction potential • Similarly, vector population will get affected

20. Effects on pathogen Virulence, aggressiveness or fecundity • Temp governs the rate of reproduction for many pathogens • Increased T duration – more number of generation- more recombinants – new virulence, more aggressive pop • Increased migration in to new areas

21. Effect on Host-pathogen interaction • CO2 favours increased disease severity by biotrophic pathogens and some necrotrophs • CO2 increases pathogen load on C3/C4 plants/grasses • Drought can aggravate the effects of soilborne diseases, like Macophomina, Fusaria and others • Temp can also influence HPI

22. Effects on Plant disease management • Delayed/adjusting planting dates less effective • Increased vulnerability to biocontrol agents • Reduced efficacy of chemical control • Risk of movement of invasive pathogen species • Reduced effectiveness of durable resistance • uncertainty for management method decision making • Changing disease management strategy

23. Models for disease prediction • Empirical models- regression models with climate variables as predictors and epidemic parameters as response variables • Simulation models based on theoretical relationships • Problems with use of such models: • Model inputs have high degree of uncertainty • Nonlinear relationships between climatic variables and epidemic parameters • Potential for adaptation of plants and pathogens • General circulation models (GCM)- based on fixed changes in temperature or precipitation has been used to predict the expansion range of some diseases- not successful

24. Effects on ecosystem Pathogen characterization might shift with climate change • Pathogen effect on host survival, physiology and reproduction • Life stages of host vulnerable to a pathogen • Proportion of individual/biomass infected at a site • Spatial distribution of infection • Rate of pathogen effects on host in relation to response and recovery • Functional similarity of infected individuals versus replacements • Frequency and duration of pathogen impact

25. Key issues with crop/disease modeling Relationship between historical climate data- seasonal forecast data - microclimate data Relationship between environment- inoculum- disease- yield Integration of crop model and disease model Interdisciplinary collaboration of agroclimatologist, modelers, agronomist, pathologist, entomologist, economist and others.. International collaboration Institutional support

26. Climate information-Disease risk management Microclimate data Crop yield model Plant disease model Met station data Historical climate dataSeasonal climate forecast Crop-disease risk model Econ input Disease risk management tool Econ benefit Crop Management advisory system A conceptual framework

27. Conclusions.. • CC first affects the disease by increasing/decreasing the encounter rates between host and pathogens by changing the ranges of the two species • Disease severity-positively correlated with increased virulence and aggressiveness of pathogens which are mediated by host resistance that is affected by climate change • CC will affect plant diseases in relation to other global change phenomena- new species, new vectors, shifts in land use, expansion of tropical/temperate areas, loss of biodiversity etc.

28. Conclusions Increased focus needed on: • How a changing environment affects host-pathogen evolution - pathogen characteristics, such as frequency of generation and proportion of sexual reproduction affect the rate of adaptation - host characteristics, such as life span affects rates of adaptation of both host and pathogen populations • Are invasive plant species better able to adapt to CC and move to new areas rapidly? • Are new invasive plant pathogens and vectors able to adapt quickly? • Local, regional and international cooperation and collaboration needed to understand the problem and find solutions