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A week's difference in heading date can alter the risk of blight.

Forrest Laws

May 8, 2020

6 Min Read
wheat1-steve-harrison-lsu.JPG
Water is misted over these wheat varieties at the Winter Wheat Misted Nursery at the LSU AgCenter’s Macon Ridge Research Station during flowering to create ideal conditions for the development of Fusarium head blight. The whitish wheat heads in the lower left of the photo are more susceptible to FHB or wheat scab than othersSteve Harrison, LSU AgCenter

Normally, Steve Harrison would be preparing to welcome farmers, seed company representatives and Extension agents to the annual Wheat and Oats Field Day at the Macon Ridge Research Station in Winnsboro, La., in mid-April.

But these are not normal times, and Harrison, wheat and oat plant breeder for the LSU AgCenter, has been recording his remarks for a first-ever virtual field day online. (www.bit.ly/deltacrops.)

University research and Extension personnel in almost every state have been working remotely to the extent they can, communicating through Zoom conferencing and adopting other safety measures to prevent the spread of the COVID-19 virus.

“We’re practicing social distancing by sending our graduate students and research associates to different fields to take notes, make selections of superior lines and do other work in preparation for harvest,” said Harrison, a professor in the School of Plant, Soil and Environmental Sciences at the Louisiana State University main campus in Baton Rouge.

“The rub will come when we start harvesting test plots in about three weeks,” he said. “I don’t know how you practice social distancing in the cab of a plot combine. We can harvest single heads and selected plants with minimal contact, but harvesting bags of seed on a plant combine is a different challenge.”

The pandemic is not the only challenging event LSU researchers have encountered in 2020. Unusually warm winter weather in Baton Rouge resulted in many of the varieties being tested on the Central Station Ben Hur Research Farm not receiving enough cold days (vernalization) to flower.

“I don’t know if you can call it climate change or not,” he said. “But about 30% of the varieties at Baton Rouge did not head out. The plots at the Dean Lee Station in Alexandria and at the Macon Ridge Research Station, which are further north, look good, in comparison.”

Fusarium head blight

What hasn’t changed this spring is the emphasis by LSU AgCenter scientists on trying to reduce the impact of Fusarium head blight or wheat scab on the state’s wheat crop, a problem shared by most of the Mid-South states.

Wheat scab, low prices and adverse weather conditions at planting time have taken a toll on Louisiana wheat farmers who have planted as many as 400,000 acres of winter wheat (in 2008). Wheat acres have now dropped so low USDA has stopped reporting them for Louisiana.

“Fusarium head blight is still a big problem across the entire region of the Mid-South,” said Harrison. “And it is consuming a lot of attention on the part of breeders who are working with resistant varieties.”

Unlike rust and other diseases in wheat, which can show up almost every year, the presence of fusarium head blight can be difficult to predict from one year to the next.

“The disease is most damaging when infection occurs at flowering and weather is warm and wet,” says Boyd Padgett, a plant pathologist at the Dean Lee Research Station. “I have seen severe scab in some fields, and, in other fields, it’s very low. This is probably due to weather conditions at flowering.”

“A week's difference in heading date can push the same variety from a weather window with high scab risk to one with a much lower risk,” Harrison said.

Wheat breeders and plant pathologists have been working hard to evaluate reaction of commercial varieties and incorporate and incorporate genetic resistance into breeding lines to develop even greater scab resistance. Information on reaction of wheat varieties to Fusarium head blight in Louisiana can be found at https://www.scabsmart.org/Louisiana_SWW.

FHB7 gene

USDA’s Agricultural Research Service recently announced the discovery and cloning of a gene known as FHB7 that can be used to develop varieties of wheat that will be more resistant to Fusarium head blight.

“Dr. Herb Ohm, a retired professor of plant breeding at Purdue University, is getting a lot of credit for that work,” said Harrison. Ohm, head of the wheat breeding program at Purdue for 41 years, retired after suffering a stroke in 2012. To learn more, visit https://ag.purdue.edu/stories/purdues-herb-ohm-sees-decades-of-work-come-to-fruition/.

FHB7 is one of a series of genes that scientists have been working with in commercial wheat varieties. “We’ve just been working with the FHB5 gene in the last couple of years,” said Harrison. “And we’re beginning to see a lot of crosses with FHB1, a gene source that came out of China.

“There are also a number of effective genes that we refer to as ‘native' that exist in our traditional breeding base,” he said. “The challenge is to use molecular markers linked to these genes in a way that lets us stack several resistance genes into one variety so that the cumulative effect is a greatly reduced infection.”

Scientists have also begun to see advances in fungicides to help with FHB. LSU researchers have been working with applications of an older fungicide, Tebuconazole, followed by a new product called Miravas Ace, which now has a label in wheat.

“Tebuconazole is active on some of the earlier wheat diseases, such as rust, and Miravas Ace is labeled on Septoria leaf spot, several other diseases and Fusarium head blight,” he said. “Miravas Ace is expensive compared to Tebuconazole, which only costs $2 or $3 an acre for the product. Miravas Ace or other fungicides with good scab activity must be timed to go on within a few days of 50% head emergence.”

Growers can go to http://www.wheatscab.psu.edu/ to see the risk of a scab epidemic in their field for a specified level of varietal resistance when their wheat is expected to begin heading. “This lets growers make informed decisions about the need to spray their fields,” said Harrison. “The website is a product of the U.S. Wheat and Barley Initiative.

“There are growers who spray fungicides prophylacticly,” he said. “But a material like Miravas Ace, which can cost upwards of $20 per acre, can have a big impact on a budget for wheat.”

Better varieties

Harrison said the varieties available to farmers now are much better from the standpoint of resistance to Fusarium head blight than they were five years. Researchers are using molecular markers along with the new genetic resistance to develop commercially acceptable varieties for their regions.

“When you combine 40 to 50% control with these split fungicide treatments with the resistant genes now available, you can grow some pretty good wheat,” says Harrison.

Another plus: Wheat researchers are collaborating more closely than ever before. Harrison and other LSU researchers are participating in the SunGrains Group, which consists of wheat breeders from the University of Florida, University of Georgia, Clemson University, North Carolina State University, University of Arkansas, Louisiana State University and Texas A&M University, he said.

“We’re constantly texting each other and sharing information each day,” he said. “The SunGrains breeders share a lot of breeding material, have uniform trials and work together closely to help each program more effectively serve growers.”

These are good times to be involved with wheat. “With wheat futures trading at $5.60 a bushel, it’s looking better than some of the other crops. Six months ago, all anybody talked about was gluten. Now everyone is at home, baking bread.”

About the Author(s)

Forrest Laws

Forrest Laws spent 10 years with The Memphis Press-Scimitar before joining Delta Farm Press in 1980. He has written extensively on farm production practices, crop marketing, farm legislation, environmental regulations and alternative energy. He resides in Memphis, Tenn. He served as a missile launch officer in the U.S. Air Force before resuming his career in journalism with The Press-Scimitar.

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