Attendees of an Aug. 20 field day check out sweet potato varieties being grown in LSU AgCenter test plots at Black Gold Farms in Delhi. Photo by Olivia McClure/LSU AgCenter

LSU AgCenter sweet potato breeder Don LaBonte talks about variety development at a field day on Aug. 20 at Black Gold Farms in Delhi. Photo by Olivia McClure/LSU AgCenter

LSU AgCenter horticulturist Arthur Villordon tells field day attendees about nutrient management in sweet potatoes on Aug. 20. The sweet potatoes on the left have shorter roots because of a nitrogen deficiency. Photo by Olivia McClure/LSU AgCenter

DELHI, La. – Despite a rainy spring that delayed sweet potato planting, the 2015 season is shaping up well, growers learned at a field day on Aug. 20 at Black Gold Farms in Delhi.

Myrl Sistrunk, LSU AgCenter extension associate, said he expects Louisiana sweet potato acreage to reach 10,000 this year, up from last year’s 8,500. Planting in northern Louisiana finished in mid-July, putting the crop two to three weeks behind schedule.

Excessive rain this spring hampered work in fields. Nutsedges, pigweed, groundcherry and some grass weeds have been problematic because the rain kept growers from making timely herbicide applications, Sistrunk said.

Attendees of the field day also heard about the latest AgCenter sweet potato research. About 150 people, including groups from Australia and Jamaica, attended.

AgCenter sweet potato breeder Don LaBonte said he is working to identify early-maturing varieties. One promising variety is LA 13-48, which has a durable skin and great shape.

“As we continually compress our planting season, that also really bunches up getting everything harvested,” he said. “There’s a need now more than ever to get an early variety in 90 days so we can start a couple weeks early.”

Beauregard continues to dominate Louisiana farms, but the newer Orleans variety is gaining popularity because of its more consistent shape. That amounts to a 10 to 15 percent increase in harvestable yield over Beauregard, LaBonte said.

The 06-52 variety, known as Bellevue, has a smooth copper skin, outstanding root consistency in all soils and stores well. “There’s very little that’s not marketable,” LaBonte said.

Growers should test their soil and adjust fertilizer applications appropriately, said AgCenter horticulturist Arthur Villordon. He showed attendees how calcium, iron and nitrogen deficiencies can negatively affect root development of sweet potatoes.

“Those are signaling compounds,” Villordon said. “We have the power to regulate what turns on and off during the crop cycle. We can turn on root development and root expansion at a certain stage by regulating our fertilizer inputs.”

Jason Chandler, of Black Gold Farms, said he is studying using 38-inch rows instead of 42-inch rows, which are more common, especially for potatoes grown for the fresh market. The smaller rows allow more efficient use of water and land, he said.

Charles Malveaux, a biological and agricultural engineering graduate student, demonstrated two types of drones, which can help identify plant health problems.

Tara Smith, resident coordinator of the AgCenter Sweet Potato Research Station, told attendees about her work to identify treatment options for nematodes. The reniform nematode, found throughout Louisiana, is most damaging to sweet potato yields and quality, but root knot nematode is also problematic.

Chris Clark, AgCenter plant pathologist, talked about his research on reducing viral infections in sweet potatoes. He said the National Clean Plant Network, which strives to ensure healthy planting stocks of specialty crops, now includes sweet potatoes and is providing the AgCenter funds to evaluate new virus detection methods.

Donnie Miller, AgCenter weed scientist, said transgenic technologies that allow row crops to tolerate 2,4-D and dicamba herbicides should be commercially available next year, which presents potential concerns for drift damage to sweet potatoes.

“We need to make sure we’re cleaning out our sprayers properly, or if you have a diversified operation, have a sprayer dedicated only to sweet potatoes,” said Miller’s graduate student, Tommy Batts, adding that as little as one-tenth of a rate can damage crops.

AgCenter entomologist Julien Beuzelin said sugarcane beetles typically appear from April to July, and again in September and October, when producers typically harvest and place roots in storage. There are few effective management options, he said.

Beuzelin said he has seen some cucumber beetles, which can be remedied with pre-plant and foliar insecticides such as Belay.

Beuzelin’s graduate student, Jie Chen, discussed her research on sweet potato weevil damage. Fewer weevil eggs hatch when laid on Murasaki sweet potatoes — a variety commonly grown in California — while the Beauregard and Evangeline varieties see more damage.

An updated budget that provides projected per-acre costs and returns for sweet potatoes is now available online, said AgCenter economist Kurt Guidry. The document, which includes cost estimates for mother beds and three harvest strategies, can be found by going to lsuagcenter.com and searching for “sweet potato budget.”

Rogers Leonard, AgCenter associate vice president, said partnerships with farms like Black Gold are critical to research.

“Many of our scientists work in greenhouses, laboratories and small plots on research stations to develop tools and technologies,” Leonard said. “Until we get them on a real farm and commercial acreage, we really don’t know how they’re going to perform.”

Funding from the state Sweet Potato Commission also benefits numerous projects, he said.

“The work at the LSU AgCenter not only benefits Louisiana, but in sweet potato-growing areas around the country,” said Rene Simon, director of the Sweet Potato Commission. “It makes me proud that we’re able to fund it.”

Olivia McClure