Impact of climate change on diseases in sustainable arable crop systems: CLIMDIS

Abstract

Climate change is predicted to lead to milder, wetter winters and hotter, drier summers for the UK. Crops will advance growth, with current wheat cultivars flowering 2-weeks earlier and being harvested three weeks earlier than traditional. ‘Mediterranean-types’ of cereals could advance these growth stages by another 2 weeks. Elevated CO₂ concentrations will increase crop productivity, as long as diseases and pests are controlled. Crops will probably move slightly to the north, with potential new crops such as maize and sunflower grown in the south of England and many diseases will change in importance only slightly. However, the risk of newly introduced diseases establishing is increased by climate change so it is important to maintain or increase statutory crop monitoring, quarantine and surveillance and to ensure that crop genotype collections keep as much diversity as possible for future breeding programmes.

More extreme weather may make certain diseases (e.g. rusts and powdery mildews) more sporadic and encourage those that develop quickly in warm conditions. Insect vectored virus and phytoplasma diseases will increase due to greater vector activity. Many contradictory effects of climate change mean that some detailed knowledge of each pathogen’s life cycle and, ideally, climate-based disease-progress models are needed. We predict that rusts and powdery mildews will become more severe after mild weather in winter and early spring (assuming some dry days will allow dispersal) but less severe after particularly hot, dry weather in summer. Summer droughts may favour other pathogens that sporulate on debris due to reduced activity by molluscs and other invertebrates. A knowledge gap exists in understanding pathogen survival and the timing of spore release to infect subsequent crops as different responses to the climate by the pathogen and crop could lead to more or less infection. More research is also needed to understand impacts of climate change on soil microbes, particularly those that mitigate root diseases such as take-all.

Generally warmer conditions will increase severity of autumn- and winter-infecting root and stem rots, while spring-infecting root and stem rots will advance with earlier crop growth and so not change in relative severity. However, yield losses from these diseases will also increase due to greater and earlier transpiration stress caused by heat or drought. Effects of increased CO₂concentrations on plant pathogens also require further research. Increased CO₂will lead to denser crop canopies, which will encourage a range of foliar diseases. Due to milder winters that will advance both crop growth and disease epidemics, T0 sprays could increase in importance. Leaf production in mid-late spring may also become so rapid that the timings of T1 and T2 sprays (relative to growth stage) will need revision in order to achieve optimal protection.

Introductions of new pathogens (‘unknown unknowns’), changes in farm practices including new crops grown, complexities of climate change projections and the biotic responses to this make prediction of the future impact of climate change on plant diseases relatively uncertain. It is therefore also important to create funding mechanisms that can allow a rapid response to research new diseases. Climate change offers the opportunity to increase crop productivity and diversify cropping systems, and emphasises the need to produce arable crops with a low carbon-footprint, while maintaining a secure and stable food supply.