Other sweet potato research projects under way in Mississippi include:

Ÿ· ŸŸŸA study by Ramon Arancibia, assistant research professor at the Pontotoc Flatwoods Experiment Station, on variety resistance to tip/end rot. The 2011-2012 study on the station showed that current commercial varieties are among the most tolerant to the diseases, Meyers says.

“In on-farm studies, he found ethephon, which some growers have expressed interest in using to help set the skin on the sweet potato root, increased the incidence of tip rot, but not end rot. He also found that fast curing (85 degrees at 85 percent humidity for five days) reduced both tip and end rot.

ŸŸ· ŸŸŸAnother study on-farm and at the station from 2010-2013 looked at the effectiveness of biofungicides to reduce the incidence of tip and end rots. Arancibia dipped sweet potato slips before planting, and also had a treatment where he sprayed the biofungicide in the furrow.

“He’s had variable results in reducing rots,” Meyers says. “We hope to get more concrete data this year. We know that rain and soil moisture at harvest also appear to be a factor in incidence of these rots, and that ethephon, regardless of the biofungicide applications, still increased tip rot incidence.

“Benny Graves, executive director of the Mississippi Sweet Potato Council, and I have two sites in Chickasaw County where we’re looking at one of the biofungicides, Serenade Soil, and a conventional fungicide, Ridomil Gold, on tip and end rots. We’re comparing 1/2-gallon per acre of Soil Serenade and 1/2-pint per acre of Ridomil Gold with non-treated plots. The applications are made in transplant water at approximately 150 gallons per acre. We’ll harvest, store, and rate them for end and tip rots.”

Ÿ· ŸŸŸŸNematodes are a significant concern for sweet potato growers, and Gary Lawrence, associate professor of biochemistry, molecular biology, entomology, and plant pathology has a study on the MSU north farm, looking at use of foliar VydateL in-furrow at planting and foliar applications for managing plant parasitic nematodes.

“VydateL is labeled for a 2 gallons per acre preplant application, but it costs $100 per gallon — an expensive treatment. He is looking at the impact of both in-furrow and foliar applications on nematode populations,” Meyers says.

“He, Mark Shankle, research professor at the Pontotoc Flatwoods Branch Experiment Station, and I are looking at a comprehensive systems approach for nematode management systems. The on-farm study in Calhoun County is comparing K-PAM, VydateL, and Mocap pre-plant and VydateL (foliar 14 and 28 days after planting) on reniform nematode populations and sweet potato injury. This covers 3.6 acres — a huge study.

“We’ll take soil samples across all plots, record nematode numbers, rate plants for vigor, and collect yields at harvest. This should give us some information on how VydateL stacks up against the other materials in Mississippi sweet potato production — basically to see if we can find more economical ways for nematode management.”

Ÿ· ŸŸŸŸWeed management: “Sweet potato growers contend with a lot of different weeds,” Meyers says, “but yellow nutsedge is one of the major problems. We don’t have a lot of options to control it right now — Dual Magnum is about the only material that’s labeled, but it requires rainfall for activation, and that’s something we don’t always get when it’s needed.

“Mark Shankle and I are conducting a study to determine yield and quality loss caused by yellow nutsedge interference at various densities. We have on-farm locations in Chickasaw County and Nash County, N.C. Hopefully, this will tell us how much yield we’re losing to nutsedge and will help aid management decisions.

“We’re also evaluating nutsedge management systems, looking at the effect of different mechanical and herbicide options for control, at one on-farm location in Chickasaw County and one on the research station. We divided fields in half. Half was cultivated, the other half was do-alled and sprayed with burndown and postemergence herbicides or a tank-mix of preemergence herbicides.

“We’re also continuing to evaluate Fierce, a new Valent herbicide, to see if it will fit in a weed management program and to determine crop safety when heavy rainfall occurs after application.”