Wheat blast, a devastating fungal disease in wheat crops, has begun spreading from South America to new continents, now causing billions in losses.
- Climate change impacts like rising temperatures, extreme weather events and atmospheric carbon fertilization now drive the expansion of wheat blast globally.
- As wheat is the most widely grown food crop worldwide, supplying about 20% of all human calories, wheat blast poses an urgent threat to global food security if impacts escalate.
- Concerted international efforts in developing resistant varieties and early warning systems provide hope to contain wheat blast, but the disease exemplifies the unexpected challenges of global food production as climate risks multiply.
Understanding Wheat Blast
- Caused by the fungus Magnaporthe oryzae Triticum
- Also known as wheat head blight and can affect other cereal crops like barley, oats, rye
- Significantly reduces yields by damaging wheat spikes and turning kernels grey or black
- First discovered in Paraná, Brazil in 1985, later spread across South America’s wheat growing regions
- Recently identified in Bangladesh in 2016, followed by infections in Zambia and now Tanzania in Africa
- Very limited treatment options – major way to curb spread is through burning infected crops
Climate Factors Enabling Wheat Blast Emergence
Multiple climatic factors enable the rampant spread of wheat blast in new areas
- Rising temperatures: Optimal temperature range for wheat blast is 25-30°C during wheat heading stage. Heat stress amplifies crop susceptibility.
- Increased humidity: Wet, humid conditions spur spore growth and dispersal
- Extreme weather: Hail, flooding, cyclones and other events can damage plants and aid infection
- Elevated CO2 levels: More atmospheric carbon stimulates fungal growth and toxin production
Global Wheat Supplies at Risk
Wheat blast’s climate-driven spread now imperils supplies of the world’s most widely grown food crop
- Over 770 million tons of wheat produced annually on 220+ million hectares worldwide
- Supplies about 20% of global human caloric intake
- South Asia and China account for over 50% of production and demand
- Africa, South America also depend heavily on wheat imports
If wheat blast becomes endemic in major growing regions, multi-billion dollar losses ensue
- Conservative models estimate over 3% global yield declines resulting in $7 billion in annual losses currently
- Epidemics causing 50% crop loss could result in $3.5 billion lost in Bangladesh alone
- Just 1-2°C temperature rise makes South Asia’s wheat 50% more blast-prone, spurring wider yield declines
Projected Climate Change Impacts on Regional Wheat Blast Risk and Supply Threats
| Region | Changing Climate Factors | Blast Risk Projections | Potential Supply Impact |
| China | Rising temps, extreme rainfall in Yellow River region | High risk areas expanding from 8 to 20 million hectares by 2050 | 5-15% yield declines could severely impact global markets |
| India, Pakistan | Temps consistently >25°C during wheat season | 40% of crop area blast-conducive by 2050 vs 10% today | 10% production loss -> $2.5 billion annual impact |
| Bangladesh | Rising coastal humidity enables spore spread inland | 50% higher wheat blast risk, epidemic frequency | Wheat either rendered infeasible or requires fungicide regimen costing $70 million+ annually |
| Brazil, Argentina | Greater moisture variability aids epidemic emergence | Increasing epidemic frequency from higher humidity before dry spells | >30% yield losses observed in current outbreaks across millions of hectares |
| East Africa | Rising highland temperatures support pathogen range expansion | Yield declines up to 20% projected as wheat blast spreads to Ethiopia, Kenya, others | Further rising import dependency or shifts to alternate grains |
Pathways for Addressing the Threat
While wheat blast’s climate change-charged spread brings new threats to global food security, researchers emphasize building resilience through integrated approaches.
Early Warning Systems
- Deploying sensors and models to predict infection risk lets farmers alter planting dates, apply fungicides
- Satellites tracking hotspots of crop damage can direct emergency response
- AI tools to diagnose crop images support real-time alerts
Developing Resistant Varieties
- Conventional breeding and gene editing methods generating wheat varieties with durable blast resistance
- Biotech approaches engineering resistance genes from other plants
- FAO and CIMMYT-led global consortium fast-tracking resistant germplasm deployment
Crop Diversification
- Rotating wheat fields with non-host crops like maize, millet, soy can curb infection carryover year-to-year
- Shifting fractions of wheat acreage to alternate grains reduces reliance on wheat supplies
The climate-enabled emergence of wheat blast in new continents spotlights how global food production enters uncharted risk territory this century. While South America and South Asia have become hotspots for crop-decimating outbreaks, early incursions into Africa also loom as harbingers of potential calamities ahead as temperatures and moisture patterns shift.