Global research to control stem rust disease saves wheat farmers losses

A study just published in Science by scientists from the University of Minnesota, CSIRO, the University of Sydney, the University of Queensland, and CIMMYT shows that research to control the wheat disease known as stem rust during 1961-2009 has added 6.2 million tons annually to world wheat harvests, worth US $1.12 billion per year at 2010 prices.

However, the emergence of Ug99, a virulent stem rust race first detected in Uganda in 1999, instigated a major problem for farmers. The disease is capable of killing wheat plants and small grain cereals, but more typically reduces foliage, root growth, and grain yields. After years of keeping stem rust at bay, Ug99 has spread from Africa to Iran, and the race is on to identify resistant genes, introduce these into locally adapted wheat varieties, and get the finished product into the hands of farmers.

Investments in breeding for resistance to stem rust have declined in recent decades, making the potential impact of Ug99 even more harmful, as most popular varieties are susceptible to the disease. A paper published in Science on 12 April 2013 presents the results of a global stem rust assessment study, which asked: Is increased investment needed for wheat stem rust research to avert crop losses from current and future strains? Using novel, probabilistic risk assessment methods, including climate suitability model s and long-term global loss data the authors estimated the economically justifiable investment in research and intervention strategies to avert future losses from stem rust.

The study found that, had there not been investment in stem rust research and ensuing effective global control during 1961-2009, losses in wheat production would have amounted to 6.2 million tons annually, or 1.3% of the total harvest. This equates to losses of US $1.12 billion per year at 2010 prices, or enough wheat to satisfy almost the entire annual calorie deficit of sub-Saharan Africa’s undernourished population. Whilst much lower than previous estimates, the losses are sizeable for the effects of just one disease on a staple food crop. This new study represents a major advance in disease-risk assessment as it accounts for variability of disease-induced crop losses over space and time.

The study concludes that “maintaining yield growth rates necessary to meet anticipated future demands will require a sustained effort to develop wheat varieties that are resistant to contemporary races of rust. This requires an investment strategy that supports sustained research programs geared to identifying and addressing ever evolving stem rust threats.” This investment strategy should amount to an economically justifiable US $51 million per year, according to the authors. Whilst this is double the value invested in recent decades, such measures are essential if we are to stop the spread of Ug99 and other new races of stem rust and improve food security for the millions of wheat-dependent consumers in developing countries.