Climate Change: Plant Disease Management

1. Climate Change: Plant Disease Management Stella Melugin Coakley Oregon State University Area in which I have been working for almost 30 years; mid 1970s, at the National Center for Atmospheric Research in Boulder Co where I became involved in questions of how climate change might impact plant pathogens…. …as part of larger conversation on provision of adequate food supplyArea in which I have been working for almost 30 years; mid 1970s, at the National Center for Atmospheric Research in Boulder Co where I became involved in questions of how climate change might impact plant pathogens…. …as part of larger conversation on provision of adequate food supply

3. 2003 Australasian Plant Pathology 32, 157-165 - Very likely = 90-99% chance. - IPCC 1996: projected range 1.0 to 3.5 C.- Very likely = 90-99% chance. - IPCC 1996: projected range 1.0 to 3.5 C.

4. Elements of Global Change Climate change--- temperature and moisture Atmospheric trace gases (CO2, O3, CH4, etc.) Land use/ land cover changes Invasive species Biodiversity loss Although tend to focus on impact of temperature and moisture on pathogens Trace gases may also directly impact host and pathogen life cycles…CO2 augmenting growth, 03 variously impacting host and pathogens Land Use/land cover changes may introduce stress factors that will increase likelihood of pathogen attacks Invasive species, in this case pathogens, may lead directly to biodiversity lossAlthough tend to focus on impact of temperature and moisture on pathogens Trace gases may also directly impact host and pathogen life cycles…CO2 augmenting growth, 03 variously impacting host and pathogens Land Use/land cover changes may introduce stress factors that will increase likelihood of pathogen attacks Invasive species, in this case pathogens, may lead directly to biodiversity loss

5. Examples from history Asian chestnut blight fungus Eliminated American chestnut and with it, several phytophagous insects In Australia, Phytophthora cinnamoni Converted large areas of Eucalyptus forest to monocot-dominated open savanna Eliminated potential nest sites and food for many animals Examples of how invasive species may impact biodiversity Pathogens cause problems not only for immediate hosts but also for associated fauna and ecological communitiesExamples of how invasive species may impact biodiversity Pathogens cause problems not only for immediate hosts but also for associated fauna and ecological communities

6. How may climate change impact disease management? Pathogens are very dependent on environment for disease development Pathogens often exist at low levels but erupt into epidemics rapidly under favorable conditions Prevention is preferable to management

7. Focus on climate warming with increased precipitation Influence pathogen Increased overwintering may > severity e.g. Mediterranean oak decline, Dutch elm disease, wheat stripe rust Influence host Rapid growth, increased canopy humidity Influence vectors of pathogens For sake of example, and to increase funding options, plant pathologists tend to think in terms of “greater disease” scenarios In truth, there will likely be increases in some diseases and decreases in others as a result of climate change Impact on Perennial crops Soil borne pathogens may be particular changesFor sake of example, and to increase funding options, plant pathologists tend to think in terms of “greater disease” scenarios In truth, there will likely be increases in some diseases and decreases in others as a result of climate change Impact on Perennial crops Soil borne pathogens may be particular changes

8. More rapid pathogen development Fungus on groundnut More rapid vector development Vector (Toxoptera sp.) of Citrus tristeza virus Increased overwintering of pathogen/vector Barley yellow dwarf, potato leafroll virus, yellows virus, Oak root rot Mechanisms of impact

9. Increased pathogen transmission Fusarium moniliforme on Capri fig Fungus on oilseed rape Increased host susceptibility Phytophthora on soybean Potato virus Y on potato Foliar rust on oats (resistance inactive) Mechanisms of impact (con’t)

10. Evidence of aphid vectors Aphids in Britain Suction trap network since 1964 First spring catch related to winter T Advance of spring flight phenology by 3 to 6 days in past 25 years (Fleming & Tatchell 1995) During same period, T increased by 0.4oC Data are for green peach aphid Aphid vectors important in virus disease transmissionData are for green peach aphid Aphid vectors important in virus disease transmission

11. Most severe and least predictable disease outbreaks When geographic ranges are altered by climate change Allows formerly disjunctive species and populations to converge Introduction of pathogen that spreads to new hosts (sudden oak death, Dutch Elm disease) Introduction of new plant which encounters pathogens native to area (wheat to Brazil, coffee to Asia) Unexpected convergence of a new host with a pathogen may lead to subsequent epidemics Diseases may exist at levels that do not attract attention until there are economic or aesthetic losses e.g. Sudden Oak Death present in wild and ignored because the tan oak species it was killing was a “weed” to forestersUnexpected convergence of a new host with a pathogen may lead to subsequent epidemics Diseases may exist at levels that do not attract attention until there are economic or aesthetic losses e.g. Sudden Oak Death present in wild and ignored because the tan oak species it was killing was a “weed” to foresters

12. Few standardized long-term data sets Overwhelming influence of management; unmanaged systems rarely monitored Few disease data sets that focus on phenology rather than disease intensity Overwhelming influence of localized variables (e.g. moisture) that may vary more under climate change Limited Prospects for Finding Climate Change “Fingerprints” for Plant Diseases Focus has been on butterflies, birds, plants -- taxa that are popular within the general public and are easily observed.Focus has been on butterflies, birds, plants -- taxa that are popular within the general public and are easily observed.

13. Uncertainty in climate change projections: IPCC 1996: ?T = 1.0 to 3.5oC by 2100 IPCC 2001: ?T = 1.4 to 5.8oC Nonlinear response: mean temperature insufficient to make accurate predictions Evolution: pathogens likely to adapt genetically Challenges for Modeling Effects of Climate Change on Plant Diseases Maximum and minimum changes may be more important Speed of change will impact ability of both the host/pathogen to evolve Stressed plant are more susceptibleMaximum and minimum changes may be more important Speed of change will impact ability of both the host/pathogen to evolve Stressed plant are more susceptible

14. Where should attention be focused? On introduction of new material History of host and pathogen populations at site of origin Prevention of pathogen introduction may not be possible but early intervention may prevent more extensive losses

15. Invasive Pests Are both cause and consequence of global change In US, cost $137 billion per year; 20% due to exotic plant pathogens (Pimentel et al. 2000) By 1991, 239 exotic plant pathogen species in US Rate of introduction: 1940-70: <5 per decade (NRC, 2002) 1990s: considerably higher - Happens globally - Anthropogenic - Has intensified over past 25 years - Has major impacts on natural and managed systems- Happens globally - Anthropogenic - Has intensified over past 25 years - Has major impacts on natural and managed systems

16. Exotic Plant Pathogens First Detected in the US in the1990s Field crops Sorghum ergot Soybean rust (Hawaii) Karnal bunt Forests Eurasian leaf rust of poplar Leaf spot of hybrid poplar Sudden oak death Needle blight of spruce Ornamentals Powdery mildew of Sedum Powdery mildew of Nandina Powdery mildew /f poinsettia Fruits and vegetables Cucurbit aphid-borne yellows virus Cucurbit yellow stunting disorder virus Powdery mildew of tomato Phytophthora rot of cabbage Plum pox virus Tomato yellow leaf curl Citrus canker Some likely introduced earlier Some pathogens are species specific, e.g. the powdery mildews Others have wide host ranges .Some likely introduced earlier Some pathogens are species specific, e.g. the powdery mildews Others have wide host ranges .

17. Temporary plateau is likely to be just thatTemporary plateau is likely to be just that

18. 1) Can Pest Invasions be Predicted? Based on life-history attributes of pest Based on invasibility of environment - - Successful invaders tended to be specialists- - Successful invaders tended to be specialists

19. Hybrids with combined host range of both parents: Melampsora ? columbiana on poplar [Newcombe et al. (2000) Mycol. Res. 104] Hybrids with new host specificity: Phytophthora sp. on alder, a hybrid between P. cambivora and a P. fragariae-like species [Brasier et al. (1999) PNAS 96] 2) Macroevolution Following Introduction of Exotic Pathogens

20. Conclusions Challenge will be rapid identification and management of new diseases Tools for management will change under changing global conditions, e.g. water quality issues may preclude use of certain chemical controls; phase-out of methyl bromide Important challenges remain in developing meaningful models of disease intensity and crop losses under climate change

21. Conclusions (con’t) Important lessons can be learned from studying patterns of pathogen invasions and pathogen evolution in response to global change Where hosts go, pathogens will follow Best management will be from exclusion or early detection and elimination where possible