Columbia Root-Knot Nematode Impact on Potato

The Columbia root-knot nematode (Meloidogyne chitwoodi) is found in the western region of the continental United States. The nematode lives in the soil and can infect potato roots and tubers. 

• Infected tubers have a bumpy or rough-looking appearance. 
• The nematodes live just under the tuber skin and cause brown spots to form. Blemishes will increase during storage. 
• Affected tubers are safe to consume. 
• The root-knot nematode causes no harm to humans. 
• Public acceptance of visual defects in tubers is low. 

Important grower information: 

• M. chitwoodi is on the list of prohibited organisms in certain trade partner countries, including Canada, the EU, and some countries in South America and Asia. 
• The presence of this nematode in shipments to countries in which the species is regulated could mean the whole shipment is destroyed. 
• There are currently no resistant potato cultivars commercially available for dealing with the Columbia root-knot nematode. 
• Fumigants and nematicides are important for controlling this nematode. 
• Decisions on how to best manage plant-parasitic nematodes in potatoes are dependent on accurate and reliable information about the number of M. chitwoodi or other plant parasitic nematodes present in a field. 
• Soils should be sampled prior to potato planting and at harvest. 

Because plant-parasitic nematodes are not found uniformly in the soil, it can be difficult to assess the nematode densities. Therefore, multiple soil samples from the field should be combined into a composite sample and sent for analysis at a diagnostic lab. 

Diagnostic labs can be contacted for specific sampling information and guidelines, but in general, combining sub-samples will minimize the variation in nematode estimates.