Despite complex regional patterns of projected climate change, significant decreases in food crop yields have been predicted using the 'worst case' CO 2 emission scenario (A1FI) of the Intergovernmental Panel on Climate Change. Overall, climate change is predicted to have a progressively negative effect on the yield of food crops, particularly in the absence of efforts to mitigate global CO 2 emissions. As with all species, plant pathogens will have varying responses to climate change. Whilst the life cycle of some pathogens will be limited by increasing temperatures, e.g. Puccinia striiformis f.sp. tritici, other climatic factors such as increasing atmospheric CO 2 , may provide more favourable conditions for pathogens such as Fusarium pseudograminearum. Based on published literature and unpublished work in progress, we have reviewed the qualitative effects of climate change on pathogens that cause disease of four major food crops: wheat, rice, soybean and potato. The limited data show that the influence will be positive, negative or neutral, depending on the host-pathogen interaction. Quantitative analysis of climate change on pathogens of these crops is largely lacking, either from field or laboratory studies or from modelling-based assessments. Systematic quantitative analysis of these effects will be necessary in developing future disease management plans, such as plant breeding, altered planting schedules, chemical and biological control methods and increased monitoring for new disease threats.

The need for pest and pathogen management will increase as the intensification of food production proceeds to feed the burgeoning human population. Climate is a significant driver of pest population dynamics, so climate change will require adaptive management strategies to cope with the altered status of pests and pathogens. A hierarchy of analytical tools is required to conduct risk assessments, inform policy and design pest management on scales from regions to landscapes and fields. Such tools include models for predicting potential geographical distributions, seasonal phenology, and population dynamics at a range of spatial and temporal scales. The level of sophistication of such models and databases will be determined by the economic importance of specific species. Many obstacles remain in the way of designing reliable adaptation strategies, and several issues that ensure continuing uncertainty are discussed. Holistic approaches that include nonclimatic drivers of change are needed to address the combination of global change variables. Changed patterns of crop production will determine the pests and pathogens that require greater effort to control. Linked crop-pest models offer the best opportunities for management of important pests and pathogens. Examples of risk assessments for pests and pathogens are illustrated mostly with cases from Australia, and guidelines for adaptation of pest and pathogen management are reviewed. The plethora of species and strains of pests and pathogens demands a parsimonious approach to risk assessment and adaptation, based on identified needs to inform management. Due to some intractable issues the best approach may often be scenario planning to design systems which will be resilient under any global change. 

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