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Root-Knot Nematode Symptoms and Identification

Learn more about symptoms of root-knot nematode infection and how root-knot nematodes are identified to species!

Symptoms Associated with Root-Knot Nematode Infection

Cultivar ‘Beauregard’ exhibiting severe galling from M. enterolobii infection.
Credit: Sam Mowery

In sweetpotato, the presence of galls on the fibrous and storage roots is a significant symptom that indicates an infection by a root-knot nematode. Cracking on the storage roots is an additional symptom that may be present. The above-ground symptoms of root-knot nematode infection can include chlorosis, stunting, and plant death. It is important to note that the presence of galls on the fibrous and storage roots are the best indicators of root-knot nematode infection, as the above-ground symptoms are relatively nondescript and look like many types of nutrient deficiencies.

Root-Knot Nematode Identification

Although above-ground and below-ground symptoms are good visual indicators for root-knot nematode infection, the determination of the root-knot nematode species can only be done through molecular techniques. With this in mind, designated diagnostic laboratories are the best resources for the identification of root-knot nematodes to species via molecular techniques.

Identification of root-knot nematodes within the field or within infected plant tissue begins with collection. Soil samples from an infected field may be collected, packaged, and sent to a diagnostics laboratory for species identification. Like soil samples, infected plant tissue can be carefully removed from the field, packaged, and sent to a diagnostics laboratory. Depending on the diagnostics laboratory, there may be differing sampling or reporting instructions, so it is best to visit their website or call prior to sampling. Given Meloidogyne enterolobii’s status as an agricultural pest, which is under quarantine in North Carolina and Louisiana, it is important to be familiar with quarantine requirements as well.

Below are links to different diagnostic laboratories within each state associated with the SweetARMOR project.

North Carolina

North Carolina Department of Agriculture & Consumer Services (NCDA&CS) Nematode Lab

South Carolina

Clemson University Plant & Pest Diagnostics Clinic: Nematode Assay Lab


Louisiana State University AgCenter (LSU AgCenter) Nematode Advisory Service


Mississippi State University (MSU) Extension Plant Diagnostic Lab


California Department of Food and Agriculture (CDFA) Nematology Laboratory