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North Carolina sweet potatoes’ biggest threatNorth Carolina sweet potatoes’ biggest threat

The regulations may be painful, inconvenient and difficult, but are vital for managing the guava root-knot nematode and maintaining North Carolina’s reputation as the leading sweet potato producing state in the country.

John Hart

October 9, 2019

6 Min Read
A North Carolina sweet potato damaged by the guava root knot nematode.Hunter Collins/Lina Quesada-Ocampo/NC State Vegetable Pathology Lab

The guava root-knot nematode has become public enemy No. 1 for North Carolina sweet potato farmers with the North Carolina Department of Agriculture issuing an internal quarantine of the invasive pest last October in all 100 of the state’s counties.

The quarantine, which remains in effect one year later, requires sweet potato seed roots to be inspected and certified free of guava root knot nematode before leaving the state. Sweet potato slips are required to have no soil or root on them before they can leave the state. The quarantine does not affect fresh sweet potatoes leaving the state.

Last year, the guava root knot nematode was found in sweet potatoes in eight counties in eastern North Carolina, which prompted the quarantine. The North Carolina sweet potato industry has remained diligent in managing the guava root knot nematode to limit its spread and impact on the sweet potato crop.

At the Sweet Potato Field Day at the Cunningham Research Station in Kinston Oct. 3, Dr. Adrienne Gorny, a nematologist at North Carolina State University, offered management guidelines for controlling the pest.


In addition, Dr. Rich Bonanno, director of North Carolina State Extension, and Dr. Sandy Stewart, assistant commissioner of NCDA, urged farmers to keep their guard up against the pest.

Stewart acknowledged the regulations may be somewhat painful, inconvenient and difficult at times. But he stressed they are vital for managing the guava root knot nematode and maintaining North Carolina’s reputation as the leading sweet potato producing state in the country.

“Because of the regulations we now have with the sweet potatoes you can grow and the transplants we can use, we will be the first state in the country to be 100 percent blue tag certified seed with sweet potatoes. That is going to be key for maintaining the kind of quality we now have, maintaining the reputation and expanding that market all across the globe,” Stewart said.

Bonanno urged all sectors of the sweet potato industry to work together and apply some peer pressure when necessary to battle the guava root knot nematode. To illustrate the importance of delivering high quality produce, Bonanno shared a story from his family farm near Boston where they had to deal damaged zucchini five years ago.

Bonanno, who managed the farm 30 miles north of Boston for 28 years prior to returning to North Carolina in February 2016 to lead the Extension Service, explained that his farm typically receives just five days a year of temperature greater than 90 degrees. But five years ago, the farm was hit with 37 days of 90 degree plus heat. This helped damage the family’s zucchini crop.

“We had diseases we had never seen before. There was a virus in the zucchini. Instead of mostly green with a touch of yellow, it was mostly yellow with a touch of green, and we could not market that zucchini,” Bonnano explained.

“We threw away about $5,000 a day of zucchini for about two weeks until that weather broke. I don’t know if any of you have ever thrown your father out of the packing house, but I had to throw my father out of the packing house because he was very concerned about what we were throwing away. He wanted to market just about all of that zucchini. It took him about five months to start talking to me again. It was about Christmas before we had a good conversation, and that was July,” Bonanno said.

“I tried to impress upon him that our reputation was at stake. At that point we had been in business for 105 years. We’ve dealt with supermarkets. We had a good market.  People respect us; they take whatever we grow. And for two or three weeks that this might be bothering the crop, we can’t jeopardize our reputation because of that,” he said.

Bonanno said this represents a different situation than the root knot nematode issue because it just impacted his family’s farm and there were no quarantines or interstate commerce issues. However, he said it illustrates the importance of not doing anything that will harm your reputation for producing high quality produce.

“When I look at this state’s situation (with the root knot nematode), I see all of those same similarities, but I see an industry that is the No. 1 industry in the country,” Bonanno said, referring to the North Carolina sweet potato industry.

For example, Bonanno noted that North Carolina supplies 60 percent of all sweet potatoes consumed in Europe. He said the state has the potential to grow that share even farther.

“We’ve got a great reputation around the world, and we can’t let that suffer. There are things we can do with this. There are things we can’t do. But I think everybody needs to take it seriously and figure out that the decisions we make in the field are not just important for the survival of us individually, but are important to the survival of this industry and ultimately for this industry in North Carolina across many, many crops,” Bonanno said.

Major Crop

In the meantime, both Bonanno and Stewart emphasized that sweet potatoes are no longer just a specialty crop in North Carolina.

“Sweet potatoes have moved up in the world here. We used to joke that people grew sweet potatoes if they were growing tobacco so some of the labor had something else to do. Now that’s kind of reversed a little bit,” Bonanno said.

Stewart noted that USDA pegs the North Carolina sweet potato crop at 93,000 acres this year, while the agency puts North Carolina’s tobacco crop at 120,000 acres. He said this shows that sweet potatoes are not a specialty crop by any means.

“This is a  major crop in North Carolina,” he stressed.

Stewart did note that tobacco has helped the North Carolina sweet potato industry because it has brought cash flow and labor to grow and nurture the state’s crop. He said sweet potatoes are an industry that the state must continue to nurture and maintaining the reputation for providing a quality product is incredibly important.

Like Bonanno, Stewart believes the European market shows a great deal more growth potential for North Carolina as do other portions of the globe. “We’ve got room to expand, but we can’t take a bunch of junk and try to expand that market. We just cannot do it,” Stewart said of the guava root knot nematode issue.

“I don’t know how many sweet potatoes we can grow. But if we can grow quality sweet potatoes, market quality sweet potatoes, expand those European markets and other foreign markets as well, it’s got to be lot bigger than 93,000 acres over time,” Stewart said.

About the Author(s)

John Hart

Associate Editor, Southeast Farm Press

John Hart is associate editor of Southeast Farm Press, responsible for coverage in the Carolinas and Virginia. He is based in Raleigh, N.C.

Prior to joining Southeast Farm Press, John was director of news services for the American Farm Bureau Federation in Washington, D.C. He also has experience as an energy journalist. For nine years, John was the owner, editor and publisher of The Rice World, a monthly publication serving the U.S. rice industry.  John also worked in public relations for the USA Rice Council in Houston, Texas and the Cotton Board in Memphis, Tenn. He also has experience as a farm and general assignments reporter for the Monroe, La. News-Star.

John is a native of Lake Charles, La. and is a  graduate of the LSU School of Journalism in Baton Rouge.  At LSU, he served on the staff of The Daily Reveille.

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