May 8, 2015
Northeast Texas wheat farmers who applied fungicides this spring could see as much as a 15 percent to 25 percent yield increase over untreated fields.
Test weights and stalk strength also will benefit from timely fungicide application, says Jim Swart, retired Texas AgriLife Extension integrated pest management specialist who is now a consultant for the Cereal Crops Research Inc. (CCRI).
West Texas wheat producers also will benefit from fungicide applications, according to Extension specialists. Oklahoma is picking up stripe rust and powdery mildew, with leaf rust at a lower level.
“After participating in two recent field days, I have observed that a fungicide (tebuconazole) application was a very good investment in wheat in Northeast Texas this year,” says Swart, who works out of Rowlett, Texas. “Most of the varieties we grow here have a significant amount of leaf and stripe rust on the uppermost leaves.”
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“Fungicide application is a big issue this year,” says Kenneth Wright, Hunt County producer. “Farmers who didn’t spray will regret it. We’ve had a lot of moisture.”
A tight window
Timely fungicide application has been problematic this spring. Wright’s son, Kendall, has a custom spray business and has worked long hours during brief dry spells to keep up with customers’ fields, as well as their own. Aerial applicators have also logged a lot of hours.
“We’ve had a very tight window to spray. We’re seeing some disease where we didn’t get good coverage,” says Collin County farmer Butch Aycock.
Over the past few years, Wright says, wheat has gained respect in Northeast Texas, to the point that comprehensive weed control, fertility and disease management make economic sense. “We used to treat wheat like a stepchild — now it’s a main crop.”
In some years, summer grains such as corn or grain sorghum might bring in more gross revenue. “But it’s the money you put in your pocket that matters,” Wright says.
Disease control has become an accepted practice, especially with the availability of a relatively inexpensive fungicide, tebuconazole.
A substantial return
“An inexpensive material like tebuconazole provides marginal benefits in wheat each and every year, regardless of disease pressure,” Swart says. “In a year with heavy disease pressure like this this one, foliar fungicides will provide a substantial return on investment. I expect to see yield increases of 15 percent to 25 percent in many of the fungicide-treated varieties being grown in this region.”
Improved yield is the most significant benefit of fungicide application, but Swart says other benefits also improve productivity.
“The fungicide treatment has multiple benefits in a year like this,” he says. “First and foremost, it allows the plant to produce more grain of a better quality — an increase in both yield and test weight. This is a direct value-added benefit at the elevator.
“Secondly, foliar plant diseases — leaf rust, stripe rust, and glume blotch — weaken the straw and increase the plant's propensity to lodge. So, it stands to reason that in wheat treated with a fungicide, straw has better standability and is less likely to lodge in a year like this.
“A third and often unnoticed benefit is that wheat treated with a fungicide can tolerate more armyworms than untreated wheat. Foliar plant diseases tend to destroy the lower leaves first, causing armyworms to move up the plants faster and threaten the flag leaves. Fungicides applied in a timely manner protect the lower leaves, allowing them to be the first food source of armyworms. If armyworms graze in the lower canopy and don’t move to the uppermost leaves, they cause no economic damage to the crop.”
Oklahoma wheat producers are also seeing disease infestations. In a recent blog post, Oklahoma State University Extension Plant Pathologist Bob Hunger reports an increase in stripe rust and powdery mildew (especially stripe rust) around Stillwater. Leaf rust also has increased, but not to the same extent (incidence or severity) as stripe rust.
“Dr. Brett Carver, OSU wheat breeder, saw significant stripe rust in his nurseries at Lahoma in north central Oklahoma. Gary Strickland, Jackson County Extension educator, also has observed an increase in stripe rust, and to a lesser extent, leaf rust, in far southwestern Oklahoma. My impression is that stripe rust has activated again with the cool, wet weather and continues to spread across Oklahoma.
“In far southern Texas, Dr. Amir Ibrahim, professor of small grains breeder/geneticist at Texas A&M AgriLife Research College Station, reports that in breeder nurseries near Castroville, he sees a mixture of stripe rust, leaf rust, bacterial leaf streak and some septoria.
“This has occurred because of back-and-forth switching between cool and warm temperatures, mixed in with lots of rain. To some extent, this also has occurred across Oklahoma during April.”
Viruses are prevalent
Mite-transmitted viruses also are prevalent in Oklahoma, Hunger says. “(Recently) in nurseries here at Stillwater I noticed occasional trapped heads scattered throughout the field.
“Using a dissecting scope in the lab, I found wheat curl mites associated with these trapped heads. Although only sporadic around Stillwater, the diagnostic lab has received multiple samples that they confirmed for presence of wheat streak mosaic virus, wheat mosaic virus (High plains virus), and/or Barley yellow dwarf virus. This includes samples from Grady, Noble, Grant, Texas and Woods Counties.”
More information on these mite-transmitted viruses can be found in EPP-7328, Wheat Streak Mosaic, High Plains Disease, and Triticum Mosaic: Three Virus Diseases of Wheat in Oklahoma.
Texas High Plains
Stripe rust and several viral pathogens have hit Texas High Plains wheat fields this spring, according to Texas AgriLife Extension and Research personnel in Amarillo.
“Stripe rust has been widespread,” says Jourdan Bell, Extension agronomist. “Because of recent rainfall, it will be cost effective to spray a fungicide.” Folicur is one good option, she says. “But we are seeing some fields with stripe rust and leaf rust, and producers may need mixed chemistry, such as Stratego.
‘We’re just suppressing disease with fungicide spray at this point,” she says. “We’re not removing it. We want to protect the yield potential.” That yield potential is variable, ranging from 20 bushels to 25 bushels on some dryland to significantly more on irrigated fields.
“We have some very good yield potential on irrigated wheat,” Bell says, “and could make some decent yields on dryland.” Spring rains came at a good time to increase potential for non-irrigated fields.
The crop has a month and a half to mature. “So far, we have had no widespread loss from hail or freeze damage, though we had one report of hail damage in Swisher County.” The crop is not in the bin yet, and Bell says farmers still remember the May freeze that caused significant injury several years ago.
Much of the High Plains wheat crop, she says, is dual-purpose, for grain and grazing. “Considering the price of wheat, feeding cattle may be a good option this year.”
Jacob Price, senior research associate under Dr. Charlie Rush at Amarillo, says they have identified “a high incidence of multiple wheat viral pathogens this season.”
Wheat streak mosaic virus and Triticum mosaic virus are the most prominent, with wheat mosaic virus at lower levels, he says. Those are transmitted by mites. An aphid transmits barley yellow dwarf, which has been detected in some locations, also at lower levels.
Price says wheat streak mosaic virus and Triticum mosaic virus are main targets this year. Those have been identified from the most northern counties of the Texas High Plains to as far south as San Angelo. “We typically find these pathogens in some locations every year, but this season has been especially bad,” he says.
The wheat curl mite is the vector for the mite-vectored viruses. “Both the mite and viruses survive between wheat seasons on volunteer wheat and some native warm season grasses,” he says. “Mites typically move from these areas after fall planting and transmit the pathogens during feeding.”
Control is a challenge. No treatment is currently available to stop the infection once it has occurred, and no miticide or insecticide is labeled to control the wheat curl mite.
Destroy volunteer wheat
Price says funding from the Texas Wheat Producers Board provides support for work on control measures. “At this time, our main recommendation is destruction of all volunteer wheat at least two weeks before planting, and also delaying planting date.
“However, we’ve found that in this area the wheat curl mite can move from areas of volunteer wheat and is capable of transmitting these pathogens during the winter, even after delayed planting. Destruction of volunteer wheat is the most important means of management.”
Another challenge is that early symptoms resemble drought and nutrient stress. “After infection, it’s very common for producers to apply valuable and expensive inputs such as irrigation and fertilizer to infected crops. This added cost only compounds the losses, which makes early detection even more important.”
Producers should send samples to the diagnostics lab at the Texas A&M AgriLife Research and Extension Center in Amarillo for pathogen testing during mid-October and again as wheat comes out of dormancy in mid- to late February.
“We have also created a Wheat Virus Early Detection System that alerts produces when these pathogens are first detected during the season,” Price says. “Our Early Virus Detection website contains information on pathogen identification, sample submission and management of wheat viral disease.”
Interested producers may become members of the system by signing up at the Texas Wheat Producers Board website, or by e-mailing Jacob Price at [email protected]
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