Louisiana-named fungus troubles wheat crop

(04/23/19) WINNSBORO, La. — While Louisiana can boast of many things — great food, fun festivals and places famous for history and hospitality — having a Louisiana-named fungus is not likely to top the list.

Fusarium louisianense is a fungal species found in Jefferson Davis Parish and is only one of many species that can wreak havoc on wheat, said LSU AgCenter plant pathologist Boyd Padgett.

“Not a good thing necessarily, but from a pathology perspective, it is pretty interesting,” he said.

Padgett was one of several AgCenter experts who spoke with approximately 50 producers, agents and industry representatives attending the wheat and cover crop field day April 12 at the LSU AgCenter Tom H. Scott Research, Extension and Education Center in Winnsboro.

Fusarium graminearum is probably the most important wheat pathogen in the country and historically the primary culprit for Fusarium head blight, or wheat scab, said AgCenter plant pathologist Trey Price.

For three of the past four seasons, it has been responsible for 15% to 25% of the wheat yield and quality losses in Louisiana, he said.

The fungus produces the mycotoxin deoxynivalenol, also known as DON, a vomitoxin that causes problems for animals that ingest it.

“In a bad scab year, you can’t sell your crop,” Price said, adding that many crops in 2017 were turned away at the elevator.

Price oversees 1,200 wheat entries in the Fusarium head blight nursery at the research station where sprinklers are set on timers overnight to create a high disease pressure environment by emulating the rainy conditions favorable for the disease. The trial area is also inoculated with the pathogen to encourage disease development.

AgCenter researchers work with pathologists and breeders across the country to identify the best variety selections by screening and rating wheat germplasm for resistance to scab disease.

Wheat research at the station includes all statewide variety trials as well as entries from the U.S. Department of Agriculture Uniform Southern Regional Nursery trials that are tested across 12 states along with the SunGrains Cooperative Breeding Program with six other universities, said AgCenter wheat breeder Steve Harrison.

About 50% of the wheat breeding resources used in the past 10 years have gone toward developing Fusarium head blight resistance, Harrison said.

“We can control leaf rust, stripe rust and lots of other things with a fungicide application. Scab, on the other hand, is whole other ballgame,” he said.

Harrison led a tour of the wheat breeding yield trials at the station where crews will soon begin to harvest about 40,000 wheat heads that exhibit good disease resistance and are the right height and maturity for use in next season’s field trials.

“Although wheat acreage is down in Louisiana, we are still contributing to advances in wheat production across the southern United States,” Price said.

Wheat acreage in Louisiana is estimated at about 25,000 acres for 2019, a slight increase of 5,000 acres from last year, Padgett said.

“Intentions were higher than that, but producers were unable to plant due to wet conditions in the fall,” he said.

A sudden drop in temperatures in early March threatened early-maturing wheat stands when plants were at the boot growth stage to head emergence, but later-maturing varieties were less affected, Padgett said.

“To our surprise, we sustained very little freeze injury overall,” he said.

AgCenter soil microbiologist Lisa Fultz said significant increases in both soil organic matter and soil microbial enzyme activity are found in results from a five-year research study on cover crops in a no-till continuous corn production system.

Improvement in the soil microbial community aids in breaking down organic material, releasing nutrients from the biomass residue and making them available for uptake by the future crop, Fultz said.

AgCenter crop scientist Josh Copes said seeding rates, planting dates and termination methods are important considerations when planting cover crops.

“Try to plant at optimal times to get a good stand,” he said, adding that risks increase with delayed planting.

Target cover crop burndown about four to six weeks from planting for corn and soybeans, he said.

AgCenter conservation agronomist James Hendrix said cover crops have to be managed like a cash crop to be successful.

Select varieties that are adapted to the area, will germinate quickly and can be easily terminated, leaving residue that can be managed for optimum benefits to soil fertility, he said.

AgCenter entomologist Sebe Brown said using seed treatments is critical for planting any crop in Louisiana because insect pressure and weather cannot be predicted.

Cover crops provide a reservoir for year-round feeding on the green biomass by both beneficial and pest insects, especially below-ground pests, and a robust seed treatment or in-furrow insecticide application will boost below-ground protection, Brown said.

Mild winter temperatures will likely result in an increase in redbanded stink bug populations that have already been spotted as early as two months ago in central Louisiana, he said.

Brown recommended budgeting for two to three insecticide applications to control stink bugs this season. “We can’t let these insects go,” he said.

AgCenter Associate Vice President Rogers Leonard encouraged field day participants to introduce themselves to legislators and educate them on the importance of agriculture to Louisiana.

“There likely will be many new faces in the state Legislature after this fall’s election cycle, and they need to understand the challenges facing producers,” Leonard said.

Agriculturalists in the state have a tremendous opportunity and challenge to remind leaders of the specific needs of the industry and its importance to the state, he said.

AgCenter regional director Melissa Cater said applications are under review and interviews will be scheduled soon to potentially fill positions for an entomologist and a soil scientist in northeast Louisiana.

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LSU AgCenter small grains breeder Steve Harrison, left, talks about plant diseases during a field day at the LSU AgCenter Tom H. Scott Research, Extension and Education Center in Winnsboro April 12. AgCenter plant pathologists Boyd Padgett, center, and Trey Price also spoke during the session. Photo by Karol Osborne/LSU AgCenter

4/23/2019 4:49:06 PM
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