What’s happening? The fungal disease wheat blast could reduce global production of the staple crop by 13% per year by 2050, according to research by international scientists. The analysis, which is the first to model how the disease will spread, warned that wheat blast could affect the world’s food security. The disease was first observed in 1985 and has since spread from South America to Bangladesh and Zambia. The researchers found that South America, southern Africa and Asia will be the worst affected regions in the future. The disease could also spread to parts of the US, Australia, China and Europe. (World-Grain.com)

Why does this matter? Wheat is one of the world’s most important crops, providing over 20% of global calories. According to the new study, wheat blast disease, which is caused by the fungus Magnaporthe oryzae, is set to spread to such an extent that up to 75% of the area under wheat cultivation in Africa and South America could become vulnerable. The disease could also spread to previously unaffected countries and regions including Uruguay, Central America, East Africa, and India. It is also likely to spread further in areas that have as yet been only slightly affected, such as Argentina, Zambia and Bangladesh. Such expansion poses a risk to global food security and the agricultural sector.

Top consumers – China is the leading global consumer of wheat by overall volume, followed by India. Both countries consume approximately 65 kg of wheat per capita. The US comes third, consuming less wheat in total, but having a higher per-capita consumption of almost 82 kg per person.  According to the new research, all three of these countries could potentially be affected the spread of wheat blast disease. However, in the US and China outbreaks are likely to be limited to these countries’ southeastern areas. In India, some parts of the country could actually become less susceptible to the infection if dry conditions combine with more frequent high temperatures of 35C or above. However, whilst they may lower the risk of wheat blast disease, such high temperatures could result in terminal heat stress, lowering yields.

Climate change impact – Under current climate conditions, 6.4 million hectares of arable land are already potentially at risk from wheat blast disease, according to the study. If climate change causes an increase in temperatures and humidity, the area vulnerable to the infection is set to rise, particularly in the Southern Hemisphere, while global wheat production could fall by 69 million tonnes per year, or 13%, by 2050.  Climate change could also see the proportion of wheat growing areas vulnerable to the disease in Oceania and North America rise from their current low levels to 5% and 12%, respectively. European regions, including Italy and parts of southern France and Spain, could also develop climates favourable to the fungus.  

Myriad threats – Wheat blast disease is far from the only threat to wheat production. Previous studies have shown that wheat yields in the Southern Hemisphere are also likely to be negatively affected by rising temperatures, variations in precipitation and higher levels of atmospheric CO2 concentrations. A study from June 2023 also found that winter wheat crops in the US Midwest and northeastern China could be damaged by an increase in extreme weather conditions linked to climate change. Russia’s invasion of Ukraine has also disrupted wheat supplies and increased prices of the grain. Prior to the start of the war in 2022, the two countries were responsible for nearly a third of global exports of wheat and barley.  

Solutions? – One way of mitigating the impact of wheat blast disease on crops could be to intensify the development of blast-resistant wheat varieties.