The 2013 wheat harvest in Louisiana is only a few weeks from beginning, and experts aren’t sure how the crop will turn out.
“This has been a trying year,” LSU AgCenter wheat breeder Steve Harrison said at the 2013 Wheat and Oat Field Day on April 17.
Some research plots were never planted due to heavy rains in December, and some grower fields were under water for a period of time. These problems were compounded by a warmer-than-normal February, followed by cooler weather and a late freeze the last week of March.
Spring freeze damage is most severe when wheat plants are just headed or pollinating, which means that earlier-heading varieties and early planted fields sustain the most damage.
“The damage that occurs may be in the form of sterilized pollen or ovules, so the heads look normal but have very low seed set,” said Harrison.
“It’s difficult to look at a field and know if freeze damage occurred without peeling back the floral parts covering the seed. Growers are sometimes unpleasantly surprised at harvest because the crop looks normal but has very low yield because of poor seed set.”
Freeze damage to early varieties shows “you have to match varieties to planting date.” Cold weather in March will probably lead to harvest beginning two weeks later than normal.
The result for this year is that early wheat shows frost damage and late wheat will mature later than normal and may have low test weight due to maturation in high temperatures.
“Identifying and developing adapted wheat varieties for Louisiana is somewhat of a challenge because those varieties need good disease resistance coupled with the right combination of response to cold temperature and day length that allow them to head out at the right time,” Harrison said.
Wheat seed was in short supply last fall, and LSU AgCenter plant pathologist Clayton Hollier cautioned against planting varieties from other regions because they may not be adapted to Louisiana.
“Stripe rust is giving us fits,” he said. Researchers have identified at least three new races in the past five years. Leaf rust, on the other hand, is not much of a problem this year, although it’s starting to develop.
Fungicides have gotten cheaper and cheaper, which Harrison sees as creating a new approach to using fungicides.
Stripe rust historically has been a problem in cooler, higher-altitude climates, Hollier said. Recently, however, “the fungus has adapted to this area.”
Statewide conditions are hit-and-miss relative to wheat quality and disease pressure.
“Although it’s not too late for a fungicide application on some varieties, in many fields, we’re too late,” said Hollier. “AgCenter people are available to help growers make decisions.”
In field tests, AgCenter researchers are evaluating various application rates and timing of fungicides to develop recommendations for Louisiana growers.
“A tremendous amount of stripe rust gave us really good tests,” said Hollier. The tests are designed to help researchers understand the pros and cons of each product and to see how each affects the pests.
“We’re looking at yield, but not necessarily economics at this time,” Hollier said. “We try to get as much information so we can tell you what we find.”
LSU AgCenter researcher Josh Lofton talked about double-cropping soybeans after wheat and his current research on managing wheat residue for double cropping. It’s “a production system well adapted for Louisiana. The key is to manage wheat residue to minimize stress on the soybean plants.”
Lofton is investigating four management techniques: leaving harvest residue and planting soybeans no-till; leaving harvest residue and tilling before planting; mowing residue and planting no-till; burning residue and planting no-till. He reviewed the first-year data.
He also reviewed the certified burn manager program for growers who want to burn wheat residue and double-crop soybeans.
LSU AgCenter researcher Rick Mascagni presented information on a USDA-funded study on waterlogging effects on wheat.
Standing water affects the plants’ root systems, reducing available oxygen and causing toxicity from water-soluble elements in the soil. Mascagni’s study is looking for genetic markers in wheat varieties that tolerate waterlogging. Plant breeders can use these markers to identify potential new varieties with characteristics to withstand waterlogging.
In the first year of the study, Mascagni has already seen differences among the wheat varieties evaluated.
LSU AgCenter weed scientist Daniel Stephenson said that while it’s too late to do anything about weeds this year, it’s good to look at what has happened and what to do next year.
He offered several suggestions for products to use depending on the weed problem and time of year. “Let us know if you have weeds that weren’t controlled by herbicides.”
AgCenter recommendations are included in the weed management guide produced each year and available online here.
“Don’t wait until February for weed control on wheat,” he cautioned.
The Hessian fly, which looks like a mosquito, has been a problem in wheat for decades in other parts of the country, said LSU AgCenter entomologist Fangneng Huang. The insect, however, has caused little problem in Louisiana wheat this year. “In our area, the problem started in 2009. Use resistant varieties to manage Hessian fly in this state.”
Growers should be aware of insects such as stink bugs coming into wheat fields from nearby ryegrass, said LSU AgCenter entomology agent Sebe Brown. “It takes quite a bit of stink bugs to reduce yields in wheat.”
Louisiana wheat fields had few problems with aphids this year, said LSU AgCenter entomologist David Kerns. “We saw a few bird cherry-oat and corn leaf aphids, but no green bugs. There’s no threshold established for bird cherry-oat aphids in Louisiana. It takes huge numbers to cause problems.”