The first line of defense against diseases that often turn a promising wheat crop into a bad dream may be the wheat itself.
“Resistance should be our first priority,” says James Swart, Extension integrated pest management specialist who works with farmers in the Texas Blackland production area.
Variety selection in the region, the northeast corner of the state, took on added importance in recent years with emergence of stripe rust, a disease that appeared only rarely until four years ago and which can result in significant yield loss.
Stripe rust infections pushed Swart and others to screen most commonly used wheat varieties as well as experimental lines. A summer crop tour, centered on plots near the Texas A&M-Commerce campus, featured variety trials as well as tests on fungicide timing, nitrogen management, and seeding rates.
Trials include both hard and soft varieties. Among the soft red winter wheat selections, Swart said Pioneer 25R37, “shows promise. It's a late-maturing variety with leaf rust and stripe rust resistance. Also, 25R47 shows good leaf and stripe rust resistance and may hold promise for the future.”
He said 25R49 is a late variety that had been productive in the past, but has shown susceptibility to the current races of leaf rust in the area. It would be a risky choice for 2004 planting. Pioneer 25R54, he said, also does not appear to carry enough leaf rust resistance to be viable in the area.
Turn to 25R57
Most farmers here have turned to 25R57. “That's the most commonly planted variety,” Swart said. “It's a little earlier than the others and is good on stripe rust but weak on leaf rust. Fungicide application may be a good bet.”
Agripro offers Natchez, a variety with high yield potential and leaf and stripe rust resistance. “Natchez has been a good yielder but it is a little on the early side,” Swart said.
Some of Syngenta's Coker varieties also may find a fit in the area. Swart said Coker 9375 has good leaf and stripe rust resistance but may be a little early for the area. “A late frost could hurt yield potential,” he said. “But this variety produced excellent yields this past year in our trials. For a tall wheat, it has excellent standability.”
Swart said they had to expand their research program to include hard red winter wheat varieties as well as soft red varieties. “Growers have asked us to try to find one or more hard red wheats that are adaptable to this region. The discounted loan price for soft wheat has make hard wheats more attractive here than they have been in the past.”
Hard red winter wheat varieties in the trial included Agripro's Jagalene, which Swart described as “topping yield tests. It has moderate resistance to leaf rust and is resistant to stripe rust. We have seen some powdery mildew problems this year, but it was an unusual year for mildew.”
Cutter, another Agripro selection, is described with “good dryland yield potential, similar to Jagalene, but straw strength is questionable for North Texas conditions. It is resistant to stripe rust but susceptible to mildew.”
Extension small grains specialist Gaylon Morgan said Ogallala shows resistance to stripe rust but may not be adaptable to Northeast Texas. He said Stanton, a variety developed for the High Plains shows resistance to Hessian fly, an occasional problem in some Blackland wheat areas, but is susceptible to both stripe and wheat rust. “It's probably not suited to this area, either,” he said.
An Agripro experimental variety, recently name Fannin, “has resistance to all three diseases (stripe and leaf rust and powdery mildew). It's one of only a few varieties resistant to mildew,” Morgan said. “Yield is comparable to Jagalene and Cutter. It was developed for the Rolling Plains and the Blacklands.” Certified seed will not be available until fall of 2005.
Swart said other soft wheats include Crawford, an Agripro selection with stripe and leaf rust resistance. “But it's an early maturity wheat so it's at risk for late frost damage.” Mason, he said, “also shows good potential but is too early for Northeast Texas. It's a good wheat for grazing and produces twice as much early forage as some of the varieties that the growers are currently planting.”
Swart said Coker 9152 has shown, “marginal resistance to stripe rust but is good on leaf rust. Coker 9295 is susceptible to stripe rust.”
He said Coker 9663, a tall wheat, still offers good yield potential, but that Coker 9375 might be a better choice.
Pioneer 25R78, he said, “looked like a world beater several years ago with good tolerance to stripe rust, but in the past two years, it has shown susceptibility to it. 25R78 continues to have good leaf rust resistance. This variety produced 100-bushel wheat this year in some of our research plots. We are considering planting some 25R78 in our student farming projects this fall, and spraying it for stripe rust if it becomes necessary. If it were not for the stripe rust susceptibility, it would be as close to the ideal variety for this region as anything we have seen.”
Uniform Variety Test
Morgan discussed results from a Uniform Variety Test, conducted on soft wheat in the Blacklands of Northeast Texas.
Progeny, he said, was not holding up for leaf rust resistance and was also susceptible to mildew. “It's not a fit here,” he said.
Ranger has leaf rust resistance and is OK on stripe rust. “Yield is still a question mark.”
He said Crawford shows resistance to the Southeast biotype Hessian fly. “We've seen four or five races of the fly,” Swart said.
Morgan said Dixie 900 shows moderate leaf rust resistance, is susceptible to powdery mildew and is OK on stripe rust.
Delta King's 1551 has moderate resistance to leaf rust. “It has the most potential of any Delta King variety for the area.”
Hard wheat selections tested included Jagalene, which shows good yield potential and holds up against stripe rust but is susceptible to leaf rust. “Be ready to spray,” Morgan said.
Overly, a Kansas State variety, is an early maturing wheat with resistance to leaf rust and powdery mildew. “But it broke for leaf rust this year,” Morgan said.
Swart said many Northeast Texas farmers grow soft red winter wheat because of the high potential for disease infection in the more humid conditions and the availability of varieties with resistance to some of the most damaging pathogens.
“But the higher price for hard wheat is attracting attention,” he said.
Swart also discussed fungicide application timing. He said early treatment works best for stripe rust and late application is better to combat leaf rust.
Variety selection is playing a role, he said. “From 60 percent to 70 percent of the acreage in the area is 25R57, but it's susceptible to leaf rust. A lot of leaf rust came in late this year and farmers who opted to spray a fungicide saw a yield advantage compared to fields not treated. This was the worst leaf rust infection we've seen in several years.”
Swart said leaf rust needs little moisture to thrive. “Morning dew provides enough moisture to trigger and infection cycle,” he said. “Leaf rust doesn't need rainfall.
He said a fungicide treatment may be justified under some conditions.
He suggests spraying for stripe rust at Feekes growth stage 8, when the flag leaf emerges. The optimum timing to spray for leaf rust is later, generally around Feekes 10 (boot). “Growers should stay away from the most susceptible varieties, but the perfect wheat variety does not exist.”
Swart said the fungicide timing trials are in their third year. Much of the wheat research is funded by producer check off monies, administered by the Texas Wheat Producers Board. Cereal Crops Research Inc. (CCRI), a nonprofit grower organization, also contributes generously to the research program. According to Swart, CCRI has donated over half a million dollars since the organization was formed in 1987.
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