Putting Science into Action to Address Threats to Food Security Caused by Crop Diseases

Crop diseases are a dangerous and recurring threat to food production that are poorly recognized by the general public or lost in the big picture by global priority setting organizations, such as the World Bank and United Nations. Moreover, disease incidence is on the rise due to increasing food production needs, climate change, and expanding international trade and travel. In developing countries, up to 80% of people are involved in farming (World Bank) under conditions of limited resources, and they are especially vulnerable to damage from crop disease. With more than 2.2 billion additional people to feed by 2050, the demands on modern agriculture are enormous, and preventing losses caused by plant diseases is a key factor for ensuring global food security. The most infamous crop disease episode in history was the Irish Potato Famine, caused by the water mold, Phytophthora infestans, whose name means the "Plant Destroyer". More commonly, the disease it causes is known as Late Blight. The severe multi-year Late Blight outbreak and the political conditions of the 1840s resulted in famine and the deaths of more than one million people and the emigration of more than another million. To this day, the population of Ireland has not returned to pre-Late Blight levels. Outbreaks of Phytophthora and numerous other plant pathogens continue around the world, causing average losses of 15% of global food production every year. Of particular concern are diseases that can cause pandemics and entire crop failure, such as wheat stem rust, wheat blast, bacterial wilt of banana and late blight of potato. Disease losses can be limited with agronomic management, agrochemicals, and breeding for varieties with disease resistance. Unfortunately, farming practices designed to maximize production efficiency and yield create opportunities for pathogens to spread, mutate, and overcome chemical sprays and genetic resistance based on single genes as seen with numerous fungal and bacterial pathogens. Disease resistance is a major goal of conventional breeding, because genetic resistance is the most effective means of disease control. Yet developing finished varieties that balance multiple yield, flavor, and other traits while achieving disease resistance is very challenging, and durable examples are few. And though the global crop protection industry develops agrochemicals to aid in disease control, in 2014 growers spent more than $14 billion on crop protection compounds to control diseases, however these were only partially effective. Whereas the combination of improved seeds and chemistry has generally produced reliable harvests in developed countries, serious unmanaged diseases of crops exist today in these areas, including stripe rust of wheat (Puccinia striiformis), citrus greening (Candidatus liberibacter asiaticus), corn stalk and ear rots (many different pathogens), and Xylella. Additionally the world's 500 million smallholder farmers, who feed one third of the world's people, have insufficient resources and access to these tools to address their very serious disease threats, including late blight of potato, maize lethal necrosis disease, and cassava brown streak disease.