New crop loss study underscores urgent need for resistant varieties

By Joan Conrow

February 20, 2019

Plant pests and diseases are significantly reducing yields of five major food crops across the globe, underscoring the critical need to develop new resistant varieties, according to a new study.

Some 137 pathogens and pests cause losses of 10 to 40 percent in the staple crops — wheat, maize (corn), soybeans, rice and potatoes — that provide about 50 percent of the calorie intake among the world’s humans, according to the study published in Nature, Ecology & Evolution.

“For chronic pathogens and pests, we need to redouble our efforts to deliver more efficient and sustainable management tools, such as resistant varieties,” said study co-author Neil McRoberts, who is a professor in the Department of Plant Pathology at the University of California, Davis, and co-leader of UC’s Agriculture & Natural Resources Sustainable Food Systems Strategic Initiative. “For emerging or re-emerging pathogens and pests, urgent action is needed to contain them and generate longer term solutions.”

Plant researchers across the globe are using genetic engineering to develop pest-resistant varieties, such as potatoes resistant to late blight disease. The drought-tolerant and pest-resistant varieties of TELA (WEMA) maize developed for sub-Saharan Africa show resistance to the new scourge of fall armyworm. Conventional breeding is also being used. The Durable Rust Resistance in Wheat Project, an eight-year international collaboration, resulted in the release of 63 varieties of stem rust-resistant wheat in 10 at-risk nations.

Many other research efforts are under way. The study authors underscored the need for haste, as diseases and pests destroy a substantial amount of food at a time when the world is struggling to feed a growing population in the face of climate change challenges to agriculture.

Meanwhile, pests and pathogens continue to rapidly adapt and spread, “amplified by globalized exchanges over continents,” the researchers wrote.

The researchers surveyed several thousand crop protection experts in 67 countries that together grow 84 percent of the five staple crops. They also focused on agricultural “hotspots” that are critical to global food security: Northwest Europe, the plains of the US Midwest, Southern Canada and China, the Indo-Gangetic Plains of South Asia, Southern Brazil and Argentina, Southeast Asia and sub-Saharan Africa. Losses tended to be lower in “hotspots” that produced a surplus, and higher in “hotspots” located in food insecure regions, the researchers found.

“The highest losses appear associated with food-deficit regions with fast-growing populations, and frequently with emerging or re-emerging pests and diseases,” McRoberts said.

The crop losses range from 10 to 28 percent in wheat, 20 to 41 percent in maize, 11 to 32 percent in soybeans, 25 to 41 percent in rice and 8 to 21 percent in potatoes, resulting in “substantial economic losses and [reduced] food security at household, national and global levels,” the authors wrote.

Also contributing to the study were lead author Serge Savary, chair of the International Society for Plant Pathology committee on crop loss; epidemiologists Paul Esker of Pennsylvania State University and Sarah Pethybridge of Cornell University; Laetitia Willocquet at the French National Institute for Agricultural Research in Toulouse, France; and Andy Nelson of the University of Twente in The Netherlands.