Climate change disease risk
From the April 2007 edition of Agriculture Today.
Climate change could alter the nature and severity of plant pests and diseases affecting agriculture, according to a speaker at a symposium on cereal rust diseases.
Speaking at the NSW Centre for Animal and Plant Biosecurity symposium, CSIRO scientist Dr Sukumar Chakraborty said realistic pest risk analyses for agriculture must take into account the impact of elevated atmospheric carbon dioxide (CO2) levels.
Dr Chakraborty said it had been assumed that higher C02 could be good for plants, by having a fertiliser effect which enlarged canopies by 30 per cent and resulted in increased yields.
“However, none of this research has considered pests or pathogens,” he said.
Rust diseases, which are caused by fungi, are regarded as a serious threat to world food supplies.
Dr Chakraborty has reviewed research on 27 different plant diseases and found that the severity of the majority of diseases is higher with elevated CO2 levels, but many of the changes were specific to the host plant and pathogen.
“At this stage we cannot generalise,” he said.
“We know that changing temperature can also tip the balance between pathogen species and that climate change can activate sleeper pathogens, whilst others may cease to be of economic importance.”
Dr Chakraborty said higher CO2 can increase the fertility of fungi, which may produce more spores, and that once they penetrate plant tissue they grow much faster.
“The number of spores can be up to 15 to 20 fold higher, leading to a massive increase in the pathogen,” he said.
“You may get new strains developing, with adaptation occurring faster. Evolution may be accelerated.”
Of the 27 diseases examined under elevated CO2 levels, 13 caused higher crop losses than expected.
Ten of the diseases had a reduced impact, and four had the same effect as they do now.
Speakers at the symposium pointed out that the impact is likely to vary with different sites and cultivars – and be worse where crops were under stress.
Dr Chakraborty said the physical location of infrastructure like silos and roads would make it difficult for agriculture to move to where the climate was more conducive.
“This means many crops will be grown under chronic stress, which is likely to make them more vulnerable to pathogens.”
Dr Chakraborty said risk assessment tools were available and needed to be used to ensure climate change was taken into account when assessing the future risks of pests.
The NSW Centre for Plant and Animal Biosecurity is a partnership between the NSW Department of Primary Industries and the University of Sydney.
