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Combating guava root-knot nematodes
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Combating guava root-knot nematodes

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FARM clemson nematodes

Bumps, knots, and cracking of a sweet potato storage root from guava root-knot nematodes.

CLEMSON – Clemson University researchers, led by nematologist Paula Agudelo, are armed with close to $7 million to design protocols for managing invasive guava root-knot nematodes.

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The funding comes from the United States Department of Agriculture, industries and universities through the Specialty Crop Research Initiative Program managed by the National Institute of Food and Agriculture. The project includes researchers from Clemson, the University of Georgia, the University of Florida, North Carolina State University and the USDA’s Agricultural Research Service.

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The guava root-knot nematode was detected in Darlington County fields in September 2017. This nematode is considered to be one of the most damaging in the world because of its wide host range, aggressiveness and ability to overcome the resistance that has been developed against root-knot nematodes in many crops.

“Guava root-knot nematodes affect sweet potato, pepper, cucumber, watermelon and tomato crops,” said Agudelo, who also is associate dean of research for Clemson’s College of Agriculture, Forestry and Life Sciences, Experiment Station director and a plant pathology professor. “The goal of our research is to enhance the resiliency of vegetable production by integrating management practices and information that help growers anticipate and respond to the threat that the spread of this nematode poses.”

The study is funded for four years, during which researchers will work to identify the prevalence and distribution of the guava root-knot nematode in vegetable crops in South Carolina, North Carolina, Florida and Georgia. Researchers will evaluate the efficacy of nematicides, cover crops and crop rotations. Researchers also will develop sweet potato cultivars that have combined insect pest and nematode resistance.

“Development of integrated management strategies will mitigate the impact of the nematode on the vegetable industry,” Agudelo said. “Knowledge about distribution of this pest will allow for quarantine measures implemented by state authorities.”

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The guava root-knot nematode is thought to be originally from China. It has been particularly damaging to guava orchards in Brazil. Discovery of the pest in South Carolina in September 2017 resulted in a quarantine of South Carolina sweet potatoes by Louisiana and Mississippi.

Steven Long, assistant director of the Clemson Department of Plant Industry, said Louisiana and Mississippi also are blocking the entrance of soil from South Carolina.

“All South Carolina commercial planting and harvesting equipment entering Louisiana and/or Mississippi must be accompanied by a certificate of inspection issued by our Department of Plant Industry,” Long said. “All South Carolina nursery stock entering Louisiana as well as Mississippi must have a soil sample and certificate from our office indicating the sample is free of the nematode.”

For more information, contact the Clemson Department of Plant Industry at 511 Westinghouse Road, Pendleton, S.C. 29670, call 864-646-2135 or E-mail

A list of South Carolina quarantines related to the guava root-knot nematode is available at

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