Prairie Grains Nov 97 - Scab Rampage

Issue 10
November 1997
Scab On a Rampage: Where Do We Go From Here?

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Prairie Grains is the
official publication of
the Minnesota
Association of
Wheat Growers,
North Dakota Grain
Growers Association,
South Dakota Wheat,
Inc., and the
Minnesota Barley
Growers Association.

Scab in small grain crops is a huge problem worldwide, and apparently getting worse. No one expects a satisfactory solution anytime soon.
What researchers do hope is that incremental successes on a number of fronts-variety development, fungicide development, new crop production practices, improved methods of handling and marketing grain-will add up, eventually, to a workable strategy that farmers can use to outsmart the disease.
Meanwhile, millions of bushels of small grain production, and billions of dollars, are being lost throughout the world to the fusarium fungi that cause scab, a disease that simultaneously reduces yield and blasts grain quality by shriveling kernels and sometimes by inducing formation of vomitoxin.
In North Dakota alone farmers lost nearly $1 billion to scab between 1993 and 1997, according to estimates by the North Dakota State University Extension Service. Total direct and indirect losses to the state's economy due to scab during that period are estimated at nearly $3 billion.
Such losses inspire some to think that recent scab outbreaks are worse than they ever have been, and maybe so. But the disease isn't new. In 1919 scab caused an estimated loss of 80 million bushels of spring and winter wheat in the United States, and between 1928 and 1937 scab epidemics continued sporadically in this country.

A worldwide problem
Other parts of the world have likewise suffered stunning losses from scab. In the '60s, '70s and '80s durum producers in Argentina were hit by scab epidemics, and in 1987 a severe epidemic struck wheat crops all over Europe, prompting the Bavarian agriculture ministry to begin monitoring cereal grains for fusarium toxins. Recent severe outbreaks in Canada and Japan have led those countries to fund extensive studies on how to control the disease.
In China, the world's largest wheat producer, scab is endemic and scab losses large. As it happens, it is from a line of scab-resistant Chinese wheat that scab-resistant wheat varieties for North Dakota are now being developed.
Today scab looms so large in the Red River Valley that people have begun to doubt whether wheat and barley are still viable crops in certain areas. The primary cause is precipitation: a series of wet years, the kind of damp in which scab thrives. Yet there have always been cycles of wet years in the area. Could scab really be a bigger problem now than it was in the past?
Yes, say crop scientists.
They point out that in three ways the agricultural situation in much of the world is quite different now than it used to be: less tillage is done, more corn is grown, and wheat varieties that form dense canopies are commonplace. And they note that the fusarium fungus persists and multiplies in infected crop residues, thrives in corn stalks, and requires the moisture that short-stemmed and dense stands of semidwarf wheat may more readily retain than did the longer-stemmed and thinner wheat stands of yesteryear.
In short, increased conservation tillage practices, increased corn production and more dense canopies of grain heads now provide nurseries for fusarium fungi that didn't exist in the past.
"All over the world corn hybrids are being adapted to grow in areas where corn has never been grown before," says Marcia McMullen, plant pathologist for the NDSU Extension Service. "In North Dakota corn is now being grown as far north as the Canadian border-and no one would have even thought of such a thing 20 years ago. And the more corn in an area, the higher the risk of scab."
Duane Berglund, extension agronomist at NDSU, agrees with many agriculturists that conservation tillage could be a contributing cause. "Years back we didn't have the kinds of conservation tillage systems that we have today," says Berglund. "We had cycles of wet years, but we didn't have all that fungus inoculum out there in surface residue from the previous crop."
Richard Frohberg, a wheat breeder at NDSU, believes today's wheat and barley varieties may actually be more susceptible to scab than were varieties grown in years past. "People wonder if our varieties are more susceptible now," says Frohberg, "and maybe they are. All these semidwarf varieties have a dense and level canopy, and you can visualize-after dew or light rain- those heads staying wet just a little longer than if you had a less dense canopy and more chance for air movement."
If the precise causes of today's scab problem seem nebulous and uncertain, so do precise solutions.
Multitudes of experts can agree on what sorts of solutions are necessary, in general. But few dare predict how well or how quickly those solutions will work. Meanwhile, large numbers of farmers suffering big financial losses are asking a single question: "Where do we go from here?"
Reassuring answers to that question are hard to come by.
What researchers do seem to agree on is that no single approach can solve the scab problem satisfactorily in the Red River Valley-or anywhere else.

The Long-Range Objective
The obvious long-range objective of scab research, notes McMullen, is to find ways to raise high-quality, scab-free wheat even in wet years, and she says there are two ways to do this. One is find new production methods for raising current varieties while cutting scab losses; a necessary short-term approach. The other is to create wheat varieties that resist scab infection; this is the ultimate and preferred solution, but not a solution that will come soon.
Frohberg has been working to breed scab-resistant wheat varieties since 1988, long before most people in North Dakota had any notion that scab could be so huge a problem.
"Being optimistic," says Frohberg, "I'd say we will have a resistant wheat variety, or wheat varieties, to release three years from now, in the winter of 2000. We have about 20 advanced lines that appear to have an improvement in fusarium head blight resistance. So if we conduct three years of testing, the winter of 2000 is when the decision would be made to release any of those varieties-assuming they continue looking favorable in the tests."
Some people wonder, in light of the very bad scab situation at present, whether a decision to release one of the new varieties might be made after only two years of testing. Frohberg doesn't know. "That is a decision that will have to be made as we go along," he says. "We just can't say now. We need the scab resistance, but on the other hand we won't do our wheat growers any good if we produce a scab-resistant variety with poor quality characteristics that will affect our export market."
Frohberg's life would be a lot simpler if all he had to do was breed for scab resistance. In addition he must breed for all the other qualities that make a wheat variety attractive to both producers and buyers-shatter resistance, resistance to lodging, high yield potential, good milling characteristics and so on. Only extensive testing can assure that a prospective new variety really meets all those criteria and won't end up causing more problems than it solves.
It is worth noting that even if a new scab-resistant variety were released by NDSU in the year 2000, that variety will not be available in sufficient supply to meet grower demand until perhaps 2002 or 2003.
Meanwhile, farmers battered by scab need to take action.

Short-Term Solutions
Here is the short list of short-term approaches that NDSU extension and research staff suggest farmers might try to alleviate the scab problem.
Consider using fungicides - Crop response to fungicides, however, has been variable, and better application techniques are needed to improve response. Also, considering the current price of wheat, fungicides are expensive.
McMullen has done a preliminary check of 1997 NDSU fungicide field trial data. The data appear promising, yet are far from reassuring to financially strapped farmers who need a solution now.
"I'm seeing a 6- to 10-bushel yield response to fungicide application in some trials," McMullen says. "But if you get a 6- or 7-bushel yield improvement by applying fungicide, you're still barely breaking even at today's low wheat prices. I think there is promise for fungicides as one of the tools to use against scab, in conjunction with everything else, because the responses I've seen so far on this year's wheat trials have been pretty good.
"But again, fungicide is an investment that comes at the end of the season, an investment that farmers aren't always prepared to make."
Do more black tillage, burying scab-harboring residue - Until we get tolerant or resistant varieties," says Berglund, "it may be that tillage changes will need to occur. Fifteen or 20 years ago we did not farm like we do today; we had black tillage or used the plow-packer and pony drill system. The tradeoff, of course, is that you lose erosion control. But we have other ways of controlling erosion, such as putting a fall cover crop on land that's going to blow."
Plant over a longer period - This, in hopes that big portions of the crop will miss scab-spawning wet weather that may appear in July and August.
"A lot of people go out there with air seeders," says Berglund, "and plant 400 or 500 acres in two or three days. Instead they should stagger that planting a little more and spread out their risk. If they planted their wheat all through May they'd have a better chance of missing that wet spell if it should occur during the heading or pollination stage." "Planting in April when possible," adds McMullen, "would result in a better chance of the crop flowering prior to July rains."
Plant another crop - Give up on wheat? This is a tricky one, since in many traditional rotations small grains are essential for breaking up the cycle of white mold that attacks soybeans, edible beans, sunflowers, canola, potatoes and so on. "In many places the soil is now loaded with white mold," says Berglund, "and it is doubtful farmers can get by with abusing the rotation for very long."
Still, alternative crops to wheat and barley are being tried in many parts of the state.
Terry Gregoire, Devils Lake area cropping systems specialist for the NDSU Extension Service, says that farmers are already trying just about every solution that's been suggested for the scab problem.
"They've switched to better varieties," he says, "and they're planting them over a wide space of time. Some are even planting into June to avoid scab. Farmers are also planting alternative crops in bigger and better ways-500,000 acres of canola, 60,000 or 70,000 acres of field peas-and less wheat and barley."
The difficulty, he points out, is that in many cases the alternatives have not proven their economic viability over the long term.
"That's why I think," says Gregoire, "we're going to see more corn and soybeans going in up here. They're risky, but wheat has been enormously risky.
"What's really happened here is that the financial risk level for farmers has been elevated tremendously. And that kind of financial uncertainty is really hard on a person who has to go in and borrow $100,000 or $200,000 to put a crop in. The guy may have $80,000 or $100,000 in equity in his land, and every year he sticks it on the line."
Earlier this month scab researchers from around the world met to share research in Szeged, Hungary, at the fifth European Fusarium Seminar. McMullen was among them.
"Forty countries were represented," says McMullen, "including the United States, Canada, Saudi Arabia, Iran, Israel, India, the Phillippines, China, Japan and Australia, as well as most European countries, and countries of Central and South America."
The organizer of the event, wheat breeder Akos Mesterhazy of Hungary, recently supplied Richard Frohberg with parental plant material that Frohberg hopes will improve his lines of scab-resistant wheat. In return, Frohberg supplied Mesterhazy with his best resistant lines, which at present are based primarily on a Chinese variety of wheat.
"It's a worldwide problem," says McMullen.
And it is likely to take worldwide cooperation - and some time - to solve it.n

Copyright Prairie
Grains Magazine
November 1997

Issue 10 November 1997	Scab On a Rampage: Where Do We Go From Here?

Library Home E-Mail Back Prairie Grains is the official publication of the Minnesota Association of Wheat Growers, North Dakota Grain Growers Association, South Dakota Wheat, Inc., and the Minnesota Barley Growers Association.	Scab in small grain crops is a huge problem worldwide, and apparently getting worse. No one expects a satisfactory solution anytime soon. What researchers do hope is that incremental successes on a number of fronts-variety development, fungicide development, new crop production practices, improved methods of handling and marketing grain-will add up, eventually, to a workable strategy that farmers can use to outsmart the disease. Meanwhile, millions of bushels of small grain production, and billions of dollars, are being lost throughout the world to the fusarium fungi that cause scab, a disease that simultaneously reduces yield and blasts grain quality by shriveling kernels and sometimes by inducing formation of vomitoxin. In North Dakota alone farmers lost nearly $1 billion to scab between 1993 and 1997, according to estimates by the North Dakota State University Extension Service. Total direct and indirect losses to the state's economy due to scab during that period are estimated at nearly $3 billion. Such losses inspire some to think that recent scab outbreaks are worse than they ever have been, and maybe so. But the disease isn't new. In 1919 scab caused an estimated loss of 80 million bushels of spring and winter wheat in the United States, and between 1928 and 1937 scab epidemics continued sporadically in this country. A worldwide problem Other parts of the world have likewise suffered stunning losses from scab. In the '60s, '70s and '80s durum producers in Argentina were hit by scab epidemics, and in 1987 a severe epidemic struck wheat crops all over Europe, prompting the Bavarian agriculture ministry to begin monitoring cereal grains for fusarium toxins. Recent severe outbreaks in Canada and Japan have led those countries to fund extensive studies on how to control the disease. In China, the world's largest wheat producer, scab is endemic and scab losses large. As it happens, it is from a line of scab-resistant Chinese wheat that scab-resistant wheat varieties for North Dakota are now being developed. Today scab looms so large in the Red River Valley that people have begun to doubt whether wheat and barley are still viable crops in certain areas. The primary cause is precipitation: a series of wet years, the kind of damp in which scab thrives. Yet there have always been cycles of wet years in the area. Could scab really be a bigger problem now than it was in the past? Yes, say crop scientists. They point out that in three ways the agricultural situation in much of the world is quite different now than it used to be: less tillage is done, more corn is grown, and wheat varieties that form dense canopies are commonplace. And they note that the fusarium fungus persists and multiplies in infected crop residues, thrives in corn stalks, and requires the moisture that short-stemmed and dense stands of semidwarf wheat may more readily retain than did the longer-stemmed and thinner wheat stands of yesteryear. In short, increased conservation tillage practices, increased corn production and more dense canopies of grain heads now provide nurseries for fusarium fungi that didn't exist in the past. "All over the world corn hybrids are being adapted to grow in areas where corn has never been grown before," says Marcia McMullen, plant pathologist for the NDSU Extension Service. "In North Dakota corn is now being grown as far north as the Canadian border-and no one would have even thought of such a thing 20 years ago. And the more corn in an area, the higher the risk of scab." Duane Berglund, extension agronomist at NDSU, agrees with many agriculturists that conservation tillage could be a contributing cause. "Years back we didn't have the kinds of conservation tillage systems that we have today," says Berglund. "We had cycles of wet years, but we didn't have all that fungus inoculum out there in surface residue from the previous crop." Richard Frohberg, a wheat breeder at NDSU, believes today's wheat and barley varieties may actually be more susceptible to scab than were varieties grown in years past. "People wonder if our varieties are more susceptible now," says Frohberg, "and maybe they are. All these semidwarf varieties have a dense and level canopy, and you can visualize-after dew or light rain- those heads staying wet just a little longer than if you had a less dense canopy and more chance for air movement." If the precise causes of today's scab problem seem nebulous and uncertain, so do precise solutions. Multitudes of experts can agree on what sorts of solutions are necessary, in general. But few dare predict how well or how quickly those solutions will work. Meanwhile, large numbers of farmers suffering big financial losses are asking a single question: "Where do we go from here?" Reassuring answers to that question are hard to come by. What researchers do seem to agree on is that no single approach can solve the scab problem satisfactorily in the Red River Valley-or anywhere else. The Long-Range Objective The obvious long-range objective of scab research, notes McMullen, is to find ways to raise high-quality, scab-free wheat even in wet years, and she says there are two ways to do this. One is find new production methods for raising current varieties while cutting scab losses; a necessary short-term approach. The other is to create wheat varieties that resist scab infection; this is the ultimate and preferred solution, but not a solution that will come soon. Frohberg has been working to breed scab-resistant wheat varieties since 1988, long before most people in North Dakota had any notion that scab could be so huge a problem. "Being optimistic," says Frohberg, "I'd say we will have a resistant wheat variety, or wheat varieties, to release three years from now, in the winter of 2000. We have about 20 advanced lines that appear to have an improvement in fusarium head blight resistance. So if we conduct three years of testing, the winter of 2000 is when the decision would be made to release any of those varieties-assuming they continue looking favorable in the tests." Some people wonder, in light of the very bad scab situation at present, whether a decision to release one of the new varieties might be made after only two years of testing. Frohberg doesn't know. "That is a decision that will have to be made as we go along," he says. "We just can't say now. We need the scab resistance, but on the other hand we won't do our wheat growers any good if we produce a scab-resistant variety with poor quality characteristics that will affect our export market." Frohberg's life would be a lot simpler if all he had to do was breed for scab resistance. In addition he must breed for all the other qualities that make a wheat variety attractive to both producers and buyers-shatter resistance, resistance to lodging, high yield potential, good milling characteristics and so on. Only extensive testing can assure that a prospective new variety really meets all those criteria and won't end up causing more problems than it solves. It is worth noting that even if a new scab-resistant variety were released by NDSU in the year 2000, that variety will not be available in sufficient supply to meet grower demand until perhaps 2002 or 2003. Meanwhile, farmers battered by scab need to take action. Short-Term Solutions Here is the short list of short-term approaches that NDSU extension and research staff suggest farmers might try to alleviate the scab problem. Consider using fungicides - Crop response to fungicides, however, has been variable, and better application techniques are needed to improve response. Also, considering the current price of wheat, fungicides are expensive. McMullen has done a preliminary check of 1997 NDSU fungicide field trial data. The data appear promising, yet are far from reassuring to financially strapped farmers who need a solution now. "I'm seeing a 6- to 10-bushel yield response to fungicide application in some trials," McMullen says. "But if you get a 6- or 7-bushel yield improvement by applying fungicide, you're still barely breaking even at today's low wheat prices. I think there is promise for fungicides as one of the tools to use against scab, in conjunction with everything else, because the responses I've seen so far on this year's wheat trials have been pretty good. "But again, fungicide is an investment that comes at the end of the season, an investment that farmers aren't always prepared to make." Do more black tillage, burying scab-harboring residue - Until we get tolerant or resistant varieties," says Berglund, "it may be that tillage changes will need to occur. Fifteen or 20 years ago we did not farm like we do today; we had black tillage or used the plow-packer and pony drill system. The tradeoff, of course, is that you lose erosion control. But we have other ways of controlling erosion, such as putting a fall cover crop on land that's going to blow." Plant over a longer period - This, in hopes that big portions of the crop will miss scab-spawning wet weather that may appear in July and August. "A lot of people go out there with air seeders," says Berglund, "and plant 400 or 500 acres in two or three days. Instead they should stagger that planting a little more and spread out their risk. If they planted their wheat all through May they'd have a better chance of missing that wet spell if it should occur during the heading or pollination stage." "Planting in April when possible," adds McMullen, "would result in a better chance of the crop flowering prior to July rains." Plant another crop - Give up on wheat? This is a tricky one, since in many traditional rotations small grains are essential for breaking up the cycle of white mold that attacks soybeans, edible beans, sunflowers, canola, potatoes and so on. "In many places the soil is now loaded with white mold," says Berglund, "and it is doubtful farmers can get by with abusing the rotation for very long." Still, alternative crops to wheat and barley are being tried in many parts of the state. Terry Gregoire, Devils Lake area cropping systems specialist for the NDSU Extension Service, says that farmers are already trying just about every solution that's been suggested for the scab problem. "They've switched to better varieties," he says, "and they're planting them over a wide space of time. Some are even planting into June to avoid scab. Farmers are also planting alternative crops in bigger and better ways-500,000 acres of canola, 60,000 or 70,000 acres of field peas-and less wheat and barley." The difficulty, he points out, is that in many cases the alternatives have not proven their economic viability over the long term. "That's why I think," says Gregoire, "we're going to see more corn and soybeans going in up here. They're risky, but wheat has been enormously risky. "What's really happened here is that the financial risk level for farmers has been elevated tremendously. And that kind of financial uncertainty is really hard on a person who has to go in and borrow $100,000 or $200,000 to put a crop in. The guy may have $80,000 or $100,000 in equity in his land, and every year he sticks it on the line." Earlier this month scab researchers from around the world met to share research in Szeged, Hungary, at the fifth European Fusarium Seminar. McMullen was among them. "Forty countries were represented," says McMullen, "including the United States, Canada, Saudi Arabia, Iran, Israel, India, the Phillippines, China, Japan and Australia, as well as most European countries, and countries of Central and South America." The organizer of the event, wheat breeder Akos Mesterhazy of Hungary, recently supplied Richard Frohberg with parental plant material that Frohberg hopes will improve his lines of scab-resistant wheat. In return, Frohberg supplied Mesterhazy with his best resistant lines, which at present are based primarily on a Chinese variety of wheat. "It's a worldwide problem," says McMullen. And it is likely to take worldwide cooperation - and some time - to solve it.n
Copyright Prairie Grains Magazine November 1997

Scab On a Rampage: Where Do We Go From Here?

Copyright Prairie Grains Magazine November 1997

Copyright Prairie
Grains Magazine
November 1997