By Olivia McClure, LSU AgCenter
MANSURA, La. – The Louisiana 2016 sweet potato harvest, which was delayed by flooding rains in August, yielded 35 percent fewer bushels than the year before, farmers were told on Jan. 18 at a meeting of the Louisiana Sweet Potato Association.
On average, farmers harvested 290 bushels of sweet potatoes per acre — considerably less than the 450 bushels per acre harvested in 2015, said LSU AgCenter extension associate Myrl Sistrunk.
“We were set up to have an excellent crop as far as yield all over the state,” he said. “It was shaping up to be good until the rains impacted us.”
Poor weather conditions also delayed planting, with many farmers unable to finish until July.
Sistrunk said some farmers struggled to find labor to plant and harvest their crop. And they will soon face stricter requirements from the U.S. Environmental Protection Agency on how they train workers who handle farm chemicals.
Louisiana had 9,296 acres of sweet potatoes in 2016, only a slight decrease from 2015’s 9,309 acres. Roughly half that acreage is located in Franklin and West Carroll parishes, Sistrunk said.
The AgCenter-developed varieties Beauregard, Orleans and Bayou Belle account for the vast majority of acreage.
AgCenter sweet potato breeder Don La Bonte said Orleans — a recent variety that shares many qualities of the popular Beauregard, which was released in the 1980s — offers consistently shaped potatoes and more that are No. 1 grade.
Among the other selections La Bonte has been studying is LA 14-31, which offers an earlier harvest to send to the fresh market and processors. A recently released variety, Bellevue, has high yields, holds up well in storage and is ideal for late shipping and sales. The red-skinned Burgundy also has high yields along with an excellent flavor, La Bonte said.
Before a variety is released, it is screened for resistance to several key diseases, said AgCenter plant pathologist Chris Clark. Two diseases that were once important are rarely seen now because all modern varieties are resistant to them, he said.
In some cases, susceptibility to a disease does not automatically disqualify a variety. It may have several good qualities, he said.
Other traits breeders look for include how well potatoes hold together when canned — something the Beauregard and Bayou Belle do well, said Paul Williams, root crop buyer for a Del Monte plant in Arkansas that uses those two varieties.
Williams said his plant had its best year so far in 2016, packing more than 60 million pounds of sweet potatoes — double the amount from previous years. Much of the plant’s supply comes from Louisiana, he said.
Thomas Proger, manager of the Lamb Weston plant in Delhi, Louisiana, said demand for sweet potatoes is growing. The Delhi facility makes 750 million servings of more than 70 products in a year, he said.
Many big-name restaurants now serve sweet potato fries and other products, especially during fall and winter as seasonal offerings, Proger said. And exports of Lamb Weston potato products to Europe have increased.
Attendees of the meeting also heard from AgCenter researchers about studies on management practices and pest control.
AgCenter agronomist Arthur Villordon explained how factors besides variety traits help determine the shape, length and number of sweet potatoes.
Too much phosphorous can reduce yields, so farmers should find out how much is in their soil before applying more, he said. And sweet potatoes grown in loose soils without a hardpan a few inches below the surface tend to become very long and thin before they start swelling outward.
“They will grow until they reach the end of the growing zone, and you’re looking at a potentially longer growing season,” he said.
Tara Smith, director of the AgCenter Sweet Potato Research Station, said insecticides such as Belay and Lorsban that are applied prior to planting can help manage sweetpotato weevils and cucumber beetles, two of the most prevalent insect pests. Pre-plant soil insecticides alone can reduce insect injury by up to 20 percent, she said.
Rain prevented many farmers from making timely applications of the Telone nematicide in 2016, and some reported heavy losses due to root knot nematode infestations. Smith encouraged farmers to sample for nematodes in the fall and use an integrated management approach.
AgCenter weed scientist Donnie Miller said two new technologies that use the 2,4-D and dicamba herbicides are expected to be available soon. Though they will offer farmers much-needed tools to combat glyphosate-resistant weeds, they may cause damage to neighboring crops if not applied correctly.
Carefully following label instructions and cleaning equipment will be critical, Miller said, because as little as one-tenth of an application rate of the herbicides remaining in spray equipment can cause severe damage and yield reductions in sweet potatoes. In a study this summer, he found that damage was worse when the herbicides were applied later in the growing season because plants had more leaf area to intercept the chemicals.