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Scab answers needed to restore wheat as cash crop

Samantha Phillips, Aaron Beaubouef, Paul Sheffield, Steve Harrison and others at Wheat Field Day
Steve Harrison, right, talks with Aaron Beaubouef, white shirt, an agricultural teacher who brought his Agronomy Team from Natchitoches Central High School in Natchitoches, La., to the field day. The team, which includes Bradley Scott, left; Samantha Phillips, Beaubouef, and Paul Sheffield, are preparing for the Agronomy Team competition at the National FFA Convention.
Louisiana State University Extension specialists searching for answers for scab dilemma in state's remaining wheat acres.

Soft red winter wheat has been a good crop for Mid-South producers. Although it rarely commanded as high a price as its cousin, hard red winter wheat, it helped pay bills when it was harvested in spring and kept a cover on barren fields in winter.

No one knows what the decline in winter wheat acres has done to the Mid-South farm economy, which was already in dire straits, but if you figure Louisiana is down about 100,000 acres with a 2016 average yield of 45 bushels and $3.50 wheat, that’s nearly $16 million in lost revenue.

Multiply that by the five states or parts of states in the Delta and pretty soon you’re approaching $100 million. So you can see why researchers, Extension specialists and growers in the region are trying to find ways to help growers return to growing wheat – profitably.

“Over the last three years, we’ve had a tremendous reduction in acreage,” said Boyd Padgett, director of the LSU AgCenter’s Central Region in Alexandria who is doubling as the state’s Extension wheat specialist. Louisiana growers planted 16,000 acres of wheat last fall, 24,000 less than the previous year, which was the lowest it had been in 37 years.

The wheat specialist and Paul “Trey” Price, Extension plant pathologist for the LSU AgCenter, say Louisiana growers “just don’t have a good taste for wheat in their mouths right now.

Scab the worst

“Over the last two years, we’ve had poor prices, environmental problems at planting or at harvest and scab,” said Dr. Padgett, speaking at the LSU AgCenter’s Wheat and Oat Field Day at the Tom Scott Research Center. “Scab is the worst it’s been in the last three years.”

Scab or Fusarium head blight was rarely seen in Louisiana until three years ago. It was primarily a disease for the northern Midwest wheat growing region, although farmers in North and South Carolina had a bout with it about 10 years ago.

“We’ve seen damage to 25 to 30 percent of the farmers’ fields in the state,” said Dr. Price, who also spoke at the field day in Winnsboro, La., in mid-April. “It’s probably in 20 to 25 percent of producers’ fields in Louisiana.”

Fusarium head blight produces the mycotoxin called deoxynivalenol. Even relatively low levels of DON, as it’s called for short, can cause problems for livestock. Hogs are most sensitive to DON, or vomitoxin, and may refuse to consume grain containing the toxin, resulting in reduced weight gain.

The symptoms include premature bleaching of the wheat heads. From the turn-row, the wheat appears ready for harvesting, but it’s not. Infected kernels will have a pinkish color and become shriveled and have a “tombstone-like” appearance.

90-percent infestation

“The pinkish color is the fungus sporulating on the plant,” said Dr. Price. “Later on they’ll turn black and you’ll see black specks in the wheat. It’s really been a devastating diseases for our state and, again, one of the main reasons our acreage is down.”

“It’s in almost every field I go to,” said Dr. Padgett. “I’m working with a grower in another parish, and probably about 90 percent of his crop is affected by this disease. It is wheat grown behind corn, which means it is at a higher risk for getting the disease.”

Part of the grower’s wheat is also grown behind grain sorghum, which is another host for the pathogen, Fusarium graminearum. One of the grower’s fields is a modified no-till and another is on a prepared seedbed, and he has scab in both. (To watch a video of Dr. Padgett’s presentation, visit

“As Trey mentioned, we don’t have any effective management practices,” said Dr. Padgett. “A combination of whatever resistance we can find, and a well-timed fungicide application is going to be your best bet. But it’s not going to eliminate it. We do have some new fungicides that may be a little better, but the verdict is still out.”

“We’re looking for varieties with resistance in cooperation with Dr. Steve Harrison (director of the LSU AgCenter’s Wheat and Oat Breeding Program),” said Dr. Price, who talked about the block of test plots containing resistant varieties from Harrison and other breeders across the South during the Wheat Field Day. (To watch a vide of Dr. Price’s presentation, visit

Three locations for trial

“We have three locations for this trial throughout the state; one’s in Crowley and one’s in Baton Rouge (in addition to the trial in Winnsboro),” he said. “We inoculated this trial. We isolate the fungus, grow the fungus out on corn actually and then we spread the fungus out across the entire trial.

“We do that because all of these varieties differ in maturity so we want to have conditions for scab the entire time across all the maturities and across all these entries out here.”

Dr. Price also is conducting a fungicide screening trial at the Tom Scott facility. The trial includes a number of triazole fungicides that have been shown to have some activity on Fusarium head blight.

“The tricky part is you have about a five-day window to make an application for scab in wheat,” he said. “The fungus infects during flowering, and it likes warm and wet conditions, and that’s a problem because you usually can’t put a fungicide application out when it’s warm, and it’s raining.

“Under the best conditions, our triazole fungicides will provide 50 percent control of scab, and when you have 90 percent scab that really doesn’t help us very much.”

New fungicide entry

The triazoles that have been most effective, he said, have been Caramba and Prosaro. “Proline has been somewhat effective, and Syngenta has a new product called Miravis Ace, an SDHI compound plus propaconazole, so that would be Adepidyn plus Tilt.”

The LSU AgCenter scientists say the search for more sources of resistance to Fusarium head blight is critical.

“I don’t think we’re going to be able to grow wheat in this state if we keep getting scab every year,” says Dr. Price. “This is the third year in a row it has just killed us and our acreage is way down.”

Wheat growers have also encountered difficulties because of the decidedly warmer temperatures of the last winter, which have interfered with the vernalization of some varieties. And there’s the price, which has plummeted because of large stocks of all types of wheat in other parts of the world.

But scab is the deal-breaker for most growers. Until researchers can find a breakthrough that will help them achieve greater control of the disease, wheat acres are likely to remain depressed in Louisiana and other Mid-South states.

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