(10/06/21) BATON ROUGE, La. — The LSU AgCenter Sweet Potato Research Station recently shared its 2021 field day video presentations.

“We’re excited about the research and extension programs, many of which focus on foundation seed production, virus testing, production research, pest management and a world-renowned breeding program,” said Tara Smith, Sweet Potato Research Station coordinator.

The entire series of presentations can be found at https://bit.ly/2YmL5Z8.

“The program in this field day highlights some of our research areas that we conduct to support the industry,” said Michael Salassi, AgCenter associate vice president and program leader for plant and animal sciences. “I’d like to thank the sweet potato industry — in particular, the Louisiana Sweet Potato Commission — for their tremendous support of the work we do.”

Don La Bonte, AgCenter sweet potato breeder, looked at some advanced lines harvested on producer Larry Fontenot’s farm in Ville Platte. These are selected from a long process that starts with tens of thousands of seeds and will continue with more years of testing and the potential of becoming a new variety:

— LA 19-20 has a little bit darker, redder skin than Orleans and Beauregard and deep orange flesh. It did well in baking trials last year. It had an amazing total yield of No. 1-rated potatoes, La Bonte said.

— LA 18-100 tastes great and has great color. It looks a lot like Orleans and Beauregard with a nice, deep orange flesh. It is close to becoming a new variety.

— LA 19-53p has deep purple flesh and tastes good, too. Researchers have been working on purples since the early 2000s, but they didn’t have good shape, flavor or color. This advanced line has given more of a mainstream No. 1 yield with a consistently nice shape. That’s something not seen in purples in the marketplace today, La Bonte said.

— LA 18-123 is another high-yield performer. It has a great shape and a lighter skin color similar to the Bellevue variety. It has nice orange flesh and is a good-eating sweet potato. It produced a good number of jumbos and No. 1s and not too many canners.

— LA 19-65 has snow-white flesh. The AgCenter is trying to develop varieties for different markets, and one of them is white-fleshed sweet potatoes. The Murasaki variety is a fabulous-tasting sweet potato, but it doesn’t grow well in heavier soils, so breeders are trying to create a white-fleshed variety that does. 19-65 may have some promise. It has more of a potato-like taste, but it has a very nice flavor and a good yield.

Some previously-released varieties developed by the LSU AgCenter continue to enjoy success:

— Bayou Belle is an early developer with well-sized roots and a nice blocky shape. It’s great for making sweet potato fries. It has a nice red skin, but it skins easily, meaning it’s not good for the fresh market. It has a sweet flavor and good disease resistance, and it grows well in heavier soils and sandy soils alike.

— Orleans is the standard fresh market variety. It has a beautiful root count and shape. It looks like Beauregard, but Orleans has a better shape and a higher grade-out of the No. 1 category. It also makes great fries.

Arthur Villordon, an AgCenter professor at the Sweet Potato Research Station, experimented with several concepts for establishing better plant yield and shape consistency.

He borrowed from a business model called 6 Sigma and applied it to sweet potato production. Transplant slips were cut from plant beds with uniform thickness, length and number of leaves compared to a row that didn’t apply these measures.

“Using the 6 Sigma approach, we had more uniform-sized No. 1 roots per hill compared to the other row where the number of roots were inconsistent in size,” Villordon said. “There’s more potential for the grower to expect higher economic return.”

Villordon also established nitrogen, phosphorus and potassium (NPK) reference strips to detect the effectiveness of using recommended nutrient inputs. Adding the recommended NPK resulted in a 57% increase in yields compared to rows with no inputs, while doubling the NPK resulted in a 15% decrease in yield.

“The results demonstrate the potential usefulness for NPK reference strips in validating fertilizer inputs and to provide guidance for future plantings,” Villordon said.

Christopher Clark, AgCenter plant pathologist, leads virus testing for the AgCenter sweet potato foundation seed program. The AgCenter Sweet Potato Plant Pathology Laboratory — which has been cleaning up foundation seed and working to prevent infection since 1999 — is part of the National Clean Plant Network for Sweet Potato (NCPN).

As part of NCPN economic studies, the AgCenter planted generation 1 (G1) seed and older generation seed from the Beauregard and Orleans varieties to accurately determine the yield and quality between the generations.

“We found older generation seed all had incidence of virus infections, but the Louisiana G1 seed was clean,” Clark said. “In other states, they already had some reinfection in their G1 seed.”

The AgCenter hopes to potentially shift and sell less clean seed storage roots and move to more greenhouse cuttings sold directly to growers. They will continue these studies for several years to see if they’re feasible.

“Over the last year, we’ve been trying an alternative to tissue culture propagation which is to use a modification of hydroponics which can be done in a lab environment so they won’t get re-infected,” Clark said. “Initially, the hydroponic plants seem to grow out a little more vigorously, but there’s a lot yet to be determined.”

Other sweet potato pathology work involves methods to improve accurate identification of micro-propagated plants and testing field plots to screen for resistance against at least 10 different diseases.

Josie Rezende, research associate with the AgCenter Department of Plant Pathology and Crop Physiology, reported collecting samples from 40 sweet potato fields in the past year. Fortunately, she did not find any guava root-knot nematodes, although research with that species continues.

“We found high levels of reniform nematodes and Southern root-knot nematodes,” Rezende said. “We do have varieties that are resistant to Southern root-knot nematodes and, although less work has been done for resistance to reniform, farmers can use nematicides and crop rotation to help manage these nematodes.”

Tristan Watson, AgCenter state nematologist, discussed the choices and effectiveness of various nematicides in two general categories: soil fumigant nematicides, which are more difficult to apply and expensive, and non-fumigant nematicides. His department also is currently evaluating the efficacy of newer nematicides and how they impact other aspects of the soil, such as the ability to preserve some beneficial soil organisms that protect against nematodes.

“The best way to detect a nematode problem is by collecting some soil samples at the time of harvest,” Watson said. “You can call the LSU AgCenter Nematode Advisory Service at 225-578-5724 for help with developing a management strategy to control the pests.”

The sweet potato weevil is the most destructive pest of sweet potatoes worldwide and it is most effectively managed through an Integrated Pest Management (IPM) approach.

“We use field level sanitation, judicious use of insecticide, clean seed, pheromone trapping systems and resistant varieties,” said Smith, an AgCenter entomologist. “Vermilion is an example of a promising recent variety that has some resistance to the sweet potato weevil.”

“Sex pheromones get the males in our traps, but we’re also trying to add volatiles, which are chemicals the sweet potatoes naturally produce so we can also get females for a better number count,” said Jeff Davis, AgCenter field crop entomologist. “In addition, we’re studying different insecticides and how they work when combined with entomopathogens — diseases that only insects get — and host plant resistance. We’ve found these combinations can almost zero out the number of sweet potato weevils on Murasaki and significantly reduce the number on Beauregard and Orleans.”

Donnie Miller, AgCenter weed specialist, described some of the best herbicide options currently available while emphasizing that there are currently no over-the-top options for sweet potatoes to take out broadleaves once they’ve emerged.

“It’s imperative to get excellent weed control before planting going into the back end of the season because we have nothing to clean it up with,” Miller said. “Valor and Reflex are the best pre-emergence options for broadleaf control, and the best choices for over-the-top coverage, immediately after slips are transplanted, are Command and Dual Magnum.”

The best time to control perennial weeds like johnsongrass and alligator weed is by applying a glyphosate herbicide once the crop is harvested, according to Miller. This provides more long-term control.

Cole Gregorie, research associate at the Sweet Potato Research Station, is working on a trial that looks at how soil phosphate availability may affect the overall root system architecture. The research pairs in-field tests with lab tests comparing negative soil phosphorus treatment of slips with positive soil phosphorus treatments.

“What we’ve seen so far is a really high correlation with increased root density with the positive soil phosphate contact,” Gregorie said.

Waana Kaluwasha, a graduate student in the AgCenter Department of Plant Pathology and Crop Physiology, presented her comparison of selective control treatments for the postharvest disease Rhizopus soft rot — the most common and destructive storage disease caused by wound-dependent fungus. For many years, Dicloran has been an effective preventative treatment, but concerns of potential pesticide residue were a reason to look for biological alternatives.

“There are some treatments that are promising and that seemed to be quite effective against Rhizopus soft rot and that are comparable to the Dicloran,” Kaluwasha said. “Bio-Save, a biological control applied as a dip or spray, works so far, and we are continuing to evaluate other options both alone and in other combinations.”

The Sweet Potato Research Station is the only facility in America whose sole purpose is to research sweet potatoes. The new varieties developed at the station are some of the most popular grown worldwide.

Arthur Villordon looks at sweet potato storage roots grown from uniform transplant slips compared to a row which didn’t apply uniform measures. The research was done on producer Larry Fontenot’s farm in Ville Platte and the results were recently presented as part of the 2021 Sweet Potato Research Station virtual field day. Photo by Randy LaBauve/LSU AgCenter

Tara Smith and Sarah Roberts take greenhouse cuttings at the Sweet Potato Research Station in Chase, Louisiana. The LSU AgCenter recently hosted the 2021 Sweet Potato Research Station virtual field day. Photo by Randy LaBauve/LSU AgCenter

AgCenter researchers dig up sweet potatoes in late September during trials of advanced lines done at the Larry Fontenot farm in Ville Platte. Initial impressions of these trials were recently presented as part of the 2021 Sweet Potato Research Station virtual field day. Photo by Randy LaBauve/LSU AgCenter

Don La Bonte evaluates sweet potatoes while Sarah Roberts collects samples during advanced line trials done at the Larry Fontenot farm in Ville Platte in late September. Advanced line LA 19-20, seen on the right row, produced an amazing number of No. 1 storage roots. Initial impressions of the harvest were presented as part of the 2021 Sweet Potato Research Station virtual field day. Photo by Randy LaBauve/LSU AgCenter