Effects of climate change on fungal diseases of trees

 

Climate change: Impacts on UK forests - Chapter 7
By David Lonsdale and John Gibbs

Key findings

• The effects of predicted climate change on fungal diseases of trees can, to some extent, be judged by analysing the existing roles of climate and of fluctuations in weather; it is, however, more difficult to predict the effects of climate change on host–pathogen relationships than on the individual organisms.
• The impact on those pathogens whose reproduction or dispersal is clearly affected by temperature is relatively predictable. 
• Warmer summers may in particular favour certain thermophilic rust fungi on poplar, which are currently rare or non-native in Britain; this has important implications for poplar breeding programmes. 
• Insect vectors of pathogens such as the fungi causing Dutch elm disease are likely to respond to warmer summers by extending their geographic ranges and hence the ranges of disease incidence. 
• The likely effects of higher year-round temperatures have been modelled in the case of Phytophthora cinnamomi, a very widespread fungus which causes root and stem-base diseases of a wide range of broadleaved and coniferous species. The models show a probable significant increase in the activity of this fungus across the UK and Europe in general. 
• Warmer winters may increase the activity of some weak pathogens, such as Phacidium coniferarum, which are active only when the host is dormant. 
• An increased incidence of summer drought would probably favour diseases caused by fungi whose activity is dependent on host stress, particularly root pathogens and latent colonisers of sapwood. 
• A reduction in the number of summer rain-days may reduce the incidence of various foliar diseases such as Marssonina leaf spot of poplar. Generally, however, it is difficult to predict the impact of climate change on pathogens whose reproduction or dispersal is strongly affected by rainfall or humidity. 
• The protective effects of mycorrhizas against various root diseases may be altered by changes in the relative fitness of different mycorrhizal fungi under conditions of altered soil temperature or moisture regime.

Next: Chapter 8 - Climate change implications for insect pests

Previous: Chapter 6 - Climate change and the seasonality of woodland flora and fauna