Climate change could result in a positive outcome for the potato industry and possibly lead to potatoes becoming one of the top staple crops in the world, says University of Pretoria (UP) Potato Pathology Programme manager Dr Jacquie van der Waals.

She says potatoes appear to be the only crop which might thrive amid increasing carbon dioxide (CO2) emissions.

Most crops are negatively affected, or not affected at all by an increase in CO2 emissions, but more potatoes are produced when the crop is faced with higher CO2 emissions.

“As a result, we actually think the potato will [likely] become one of the top three staple crops in the world. “Currently, the top three staple crops are maize, wheat and rice, with potatoes at number four, but the current top three staples will be unaffected or negatively affected by the increase in CO2 emissions,” says Van der Waals.

However, she warns about the risk of some potato diseases increasing in intensity as a result of rising temperatures. The diseases would need to be overcome first to ensure the potato industry’s success.

The UP’s Potato Pathology Programme initiated a climate change project last year, in collaboration with other researchers at UP and the Wageningen University and Research Centre, in the Netherlands. Its aim was to model South Africa’s climate between 1960 and the present, and to determine how it is likely to change up to 2050, as well as the likely impact of climate change on potato diseases.

The Council for Scientific and Industrial Research provided modelled weather forecasts on which the study was based.

The results of the study were compiled over the past three to four months and will be published in September.

“We measured temperature and rainfall patterns to determine the likely changes in intensity of the five most common potato diseases and pests in South Africa,” Van der Waals explains.

The study concluded that South Africa’s temperature would rise by between 1.5 °C and 2 °C by 2050 in the inland regions, while the coastal areas will not warm as rapidly, owing to temperature regulation by the ocean.

In addition, it was determined that the total amount of rainfall will not drastically change, but rainfall patterns, however, will change with regard to timeframe and volume.

“The study analysed late blight, early blight, Pectobacterium and Dickeya, root knot nematodes and aphids (as vectors of Potato Virus Y) to determine whether they are likely to increase or decrease as a result of global warming. “This will enable potato farmers to adapt their management strategies accordingly,” Van der Waals states.

The five diseases were modelled in four different climates in three different regions – the Sandveld, in the Western Cape, with its dry summers and wet winters; the Limpopo area, with its dry winters; and the eastern Free State, with its wet summers.

Van der Waals says the researchers determined that the only disease not likely to increase in intensity is late blight – a devastating disease that was responsible for the Irish Famine between 1845 and 1852.

“The occurrence of late blight is likely to decrease in the eastern Free State because of the change in rainfall patterns and a rise in temperature, as it is a pathogen that likes cool weather conditions,” she points out.

However, the other four diseases are likely to increase in intensity, as the pathogens respond to warm conditions.

“We have already started to see an increase in the occurrence of these diseases over the past ten years. Except for late blight, and in terms of all of the diseases, global warming is not a good scenario for the agriculture industry,” Van der Waals stresses.

Potato diseases can have a devastating impact on farmers, as they either affect the foliage of the plants, which affects their ability to photosynthesise, or the appearance of the tubers, which reduces the market value of the produce.

“Researchers have to find ways to manage and control the diseases to increase the plants’ resistance to them and aid farmers in producing better crops,” says Van der Waals.

The UP’s Potato Pathology Programme focuses on research management strategies to help control the potential increase in these diseases and urges farmers to look at either planting resistant cultivars or changing their management options to combat early blight, Pectobacterium and Dickeya, nematodes and aphids.

“Methods to combat the effects of global warming will not put greater financial pressure on farmers, as they will only need to employ a paradigm shift,” she concludes.

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