History yields clues to Canada's most devastating cereal crop disease

from Western Grains Research Magazine
January 2004

Lessons from history are providing important clues to the causes and potential solutions for Fusarium Head Blight (FHB), Canada's most costly and challenging cereal crop disease, says a prominent Fusarium research pioneer.

"To the general public and to many producers, FHB seems to be a new problem, but that's not the case," says Dr. Bob Stack, a researcher and professor of plant pathology at North Dakota State University. "Fusarium is something producers throughout North America have dealt with for a very long time." Learning from this history, he says, is key to understanding and managing a cereal crop disease that scientists are calling remarkably complex and elusive.

For example, the increased production of corn in traditional small grain growing areas over the last 25 years has likely helped drive the spread of Fusarium into the Prairies, says Stack, who recently authored the historical chapter of a definitive new book on the disease, published by the American Phytopathological Society.

"All of the evidence that corn plays a role in FHB is circumstantial. As scientists, we would like to see experimental evidence that shows a direct connection. However, if we were in the legal system rather than in the scientific system, the weight of circumstantial evidence pointing to corn's role in Fusarium's rise would make it no problem to get a conviction."

This and more of Stack's observations on the history of FHB are the subject of a feature article in the January 2004 edition of Western Grains Research Magazine, available on the Western Grains Research Foundation (WGRF) Web site: www.westerngrains.com. Western Canadian wheat and barley growers are major investors in wheat and barley breeding research through the Wheat and Barley Check-off Funds, administered by WGRF. The Research Magazine offers "Ideas and issues for farmer research investors."

Over the past decade, FHB has risen from decades of obscurity to become the most costly and challenging grain disease of the past 100 years. Annual losses in Canada alone now range from $50 to $300 million annually, totaling over $1 billion since the early 1990s. As scientists struggle to get a handle on the disease and develop control options for growers, many fundamental questions remain. Where did it come from? Why has it spread? What is the secret to long-term solutions?

These are questions that history provides valuable perspective on, says Stack. For instance, past epidemics point to several contributing factors to Fusarium's modern rise.

"Historical outbreaks of FHB can be traced to several causes: widespread planting of highly susceptible cultivars, presence of colonized residue from previous crops, presence of corn in rotation with small grains, and weather favourable for infection," says Stack. "For many years, a strong enough combination of these factors to produce outbreaks has been absent. But today, the expansion of corn, reduced tillage and weather conditions have returned us once again to a more favourable environment for FHB."

As for the prospects of obtaining strong, sustainable solutions, Stack is cautiously optimistic.

"Not since the stem rust situation in the 1950s has such a concentration of effort been marshalled against one crop disease," says Stack. "Since the early 1990s, we now know quite a bit more about Fusarium resistance - the genetics of resistance and expression of resistance. Significant breeding progress has been made, but consistent delivery of resistant varieties will require a sustained long-term effort."

The key question, he adds, is whether or not this extensive research investment will pay off with resistant varieties farmers will want to grow. "The answer had better be 'yes.' And I think it will be. When one considers the millions lost to Fusarium every year, it's clear that any future resistant varieties that achieve significant acreage can make a large impact."

As one example of a success story, in North Dakota the moderately resistant variety Alsen was released in 2000. By 2002 and 2003, Alsen was grown on 0.9 and 1.1 million hectares, respectively. "This is evidence that farmers will grow FHB resistant wheats if such varieties are of acceptable yield and quality," says Stack.

Western Grains Research Foundation is funded and directed by Western crop producers, and allocates approximately $5 million annually to research through the Wheat and Barley Check-off Funds and a separate $9 million Endowment Fund.