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Timing proves crucial to wheat management

Foliar fertilizer applications probably will not be enough to pull wheat out of late-spring nitrogen deficiencies. Seed treatments are not working to control Hessian fly infestations. Proper timing for nitrogen topdress and fungicide applications are critical for crop success. And farmers typically plant too many wheat seeds per acre in Northeast Texas.

That’s the gist of information picked up recently during an impromptu tour of wheat applied research plots.

Texas Extension IPM Agent Jim Swart, who works out of Texas A&M-Commerce, learns a lot from the test plots he has scattered across Northeast Texas in cooperative farmers’ fields.

This spring he’s looking at Hessian fly management systems, including resistant varieties, planting date and seed treatments. He’s also evaluating seeding rates, nitrogen application rates and timing and fungicide programs, primarily for leaf rust and stripe rust.

Swart recently updated Ron French, Extension plant pathologist, from Amarillo, on fungicide research plots and invited Southwest Farm Press to tag along.

Swart said Northeast Texas wheat farmers have relatively little damage from Hessian fly this spring. Last year, infestation was heavy across the area, resulting in hundreds of thousands of dollars in damage.

Big difference this year is planting date. Swart says most farmers delayed planting until November and missed the peak fall fly emergence.

“If I could pick one day to plant all my wheat in this area it would be November 1,” Swart says. “Farmers sometimes want to get in earlier, in October, to get ahead of the fall rains, but we try to keep them out of the field as long as possible.”

Swart looked at other Hessian fly management techniques this year, including seed treatments.

“Seed treatments are not effective for controlling Hessian fly,” he says. He stopped by a test plot where he evaluated several seed treatments and variety tolerance. None of the treatments on susceptible varieties escaped severe damage. “We were hoping to get some control from seed treatment.”

“Resistant varieties did well,” Swart says. “We planted three, two soft and one hard variety.”

He says an older AgriPro variety, Crawford, shows good resistance to Hessian fly. “It also looks good agronomically.” An experimental variety from Texas A&M shows promise for Hessian fly resistance, too. An Oklahoma selection is also resistant, but it may not be as adapted to this region as the soft wheats.

Swart says the resistance plots showed “a stark contrast between tolerant and susceptible varieties. I’ve never seen that strong a contrast in anything I’ve done in 25 years.”

A resistant variety may be a good option for growers in fields with a history of Hessian fly infestation.

Swart says growers were beginning to see evidence of stripe rust in mid-April and expected leaf rust to show about two weeks later. “The key is to get ahead of the disease,” he says. “Don’t get behind it.”

He says applying fungicides too late allows the disease to disrupt photosynthesis and reduce yield potential.

If stripe rust comes in early, two fungicide applications, at a half rate each, and about three weeks apart, show best results. He says growers can wait longer on leaf rust and take it out with one fungicide application around heading.

“Stripe is a colder season disease and gets started earlier,” he says. “We sometimes need two applications to take care of it.”

Seeding rate plots demonstrated differences among planting rates as low as 30 pounds per acre and as high as 240 pounds per acre. “We look at 30, 60, 90, 120 and 240 pounds per acre,” Swart says. “A 90-pound per acre seeding rate produces the most grain, although we typically don’t make enough extra wheat over the 60 pound rate to pay for the cost of quality seed.”

He says growers typically want to plant 120 bushels per acre. “We’ve demonstrated that anything more than 90 pounds is a waste of seed. And at rates over 120 pounds, the stand is so thick plants compete against each other. Wheat becomes a weed.”

Swart’s nitrogen tests show that a late spring sidedress application of about 100 pounds per acre is best for optimum growth. He says an earlier application, Feb. 1, begins to show nitrogen deficiency by mid-April.

“Most years, 100 pounds of nitrogen is enough,” he says. “If we follow corn or grain sorghum with wheat we may need 50 to 60 pounds of nitrogen to get the crop going and to help the residue decompose. Following a heavy residue crop, our standard practice is 50 to 60 pounds in January and another 100 pounds in early March. If we follow soybeans, we see no advantage to adding more than 100 pounds of nitrogen.”

He says if he could apply nitrogen on only one day, March 1 would be his choice.

Swart says some growers have seen nitrogen deficiencies this year, following several heavy rains that caused denitrification losses, especially in heavier soils.

“With a lot of big rains some fields have run out of nitrogen. The heavier the soil the more nitrogen loss.”

Foliar nitrogen application may not help. “I don’t think foliar application of nitrogen will be the solution to severe nitrogen deficiency. I’ve also asked wheat specialists about diluting 32 percent nitrogen with water. They say it’s not likely to be effective without the potential to burn the wheat.”

Swart also stopped by a weed control plot where he’s used Axial herbicide to take out ryegrass, which has developed herbicide resistance.

“Axial was available for the first time last year,” he says, “ and it looks like it’s a good product for ryegrass.”

He says one application, in January after weeds have emerged, is adequate.

Swart says the Northeast Texas wheat crop looks very good this spring. “We have good moisture.”

He says acreage will at least equal last year. “We had a good open fall to plant.”

Farmers have had to push to get corn planted before the insurance deadline, April 15. “A lot of farmers want to plant corn because of the price,” he says. “But we may see some milo in fields where they couldn’t plant corn on time.”

He says milo may come with a few problems, especially in fields where wheat was abandoned last year. “A lot of those have grown up in rhizome Johnsongrass,” Swart says. “Johnsongrass is trouble in grain sorghum.”

French says leaf and stripe rust are not big problems so far this spring in the High Plains. Virus diseases may be more prevalent. He says irrigated wheat looks very good but dryland production has suffered from prolonged drought.

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