Carolinas Tobacco, Sweet Potatoes: Aggressive Nematodes – New Research

Photo: Corteva Agriscience

The Carolinas’ wet 2018 growing season presented tobacco and sweet potato growers with many challenges. Among those was achieving control of a relatively new species of root-knot nematode, Meloidogyne enterolobii.

Meloidogyne enterolobii is considered a highly aggressive species,” said Lindsey Thiessen, Plant Pathologist at North Carolina State University. “It is very successful at causing infection with high rates of infection on the roots of host plants and causes more severe galling on host plants than other nematodes.”

The nematode, M. enterolobii, was identified in Florida more than a decade ago and was documented in North Carolina in 2011. Its presence has also been positively identified in South Carolina and Louisiana. M. enterolobii is a root-knot nematode, but it is a distinct species from the southern root-knot nematode, Javanese root-knot and peanut root-knot species that generally infect specific hosts in the southern United States.

More aggressive than other species, M. enterolobii has a wide host range, spreads rapidly and swiftly reproduces. There are currently no resistance traits available in commercially grown crops, including tobacco and sweet potato. It also breaks down any available resistance to other nematode species.

Yield losses from M. enterolobii can be substantial, and the especially damaging nematode species pulls nutrients away from tobacco foliage, causing wilting and reductions in harvest quality.

Even after fumigation, populations of this nematode are quick to return to previous levels. M. enterolobii overcomes all known root-knot nematode resistance genes. Currently, grapefruit, sour orange, garlic and peanut are considered non-hosts.

In 2017, Thiessen’s research showed the best treatments for M. enterolobii in tobacco were Telone II soil fumigant, Telone II plus chloropicrin, or Telone II followed by another chemistry. In each trial, Telone II was applied as a drench treatment or a transplant water application.

While the untreated control plot experienced 53 percent root galling, root galling in the plot treated with Telone II was significantly reduced. According to the study’s results, plots receiving Telone II soil fumigant experienced 26 percent galling, Telone II plus chloropicrin had 17 percent galling, and Telone II followed by an insecticide/nematicide had 13 percent root galling.

“It’s imperative to achieve control to minimize economic damage to both tobacco and sweet potato growers,” Thiessen said.

To optimize fumigant activity, Thiessen recommends preplant soil be in working condition with adequate soil moisture, not hard-panned, and with optimum soil temperatures of 40 to 85 F.

Researchers, including Thiessen, are excited about the potential control offered by an experimental contact nematicide produced by Corteva Agriscience, Agriculture Division of DowDuPont. The nematicide is currently included in university nematode control studies as Q8U80. This experimental product, which contains the active ingredient, fluazaindolizine, may give tobacco and sweet potato growers another tool in their battle against M. enterolobii and other yield-reducing nematodes.

“There is a need for more labeled chemistries to fight this nematode,” Thiessen says.

For more information about recently published research on this topic, visit here.

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