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How to Manage Pests

UC Pest Management Guidelines

Corky ringspot appears as brown arcs or rings in tubers.


Corky Ringspot

Pathogen: Tobacco rattle virus (TRV)

(Reviewed 8/07, updated 8/07)

In this Guideline:


Aboveground symptoms of corky ringspot rarely occur. Symptoms in tubers vary depending on virus strain, potato variety, temperature, and time of infection. Symptoms include rings of dark brown corky layers in the tuber that alternate with rings of healthy tissue. Internally, small brown flecks are diffused through the tuber. This symptom can be confused with symptoms caused by alfalfa mosaic, which is often more common than corky ringspot.


Tobacco rattle virus is transmitted by stubby root nematodes (Paratrichodorus spp.). Young potato roots and tubers are infected with tobacco rattle virus when virus-infected nematodes feed on them. The virus is also transmitted in infected tubers. Other hosts of the virus include nightshades, pigweeds, shepherd's-purse, purslane, cocklebur, and sunflower.


Plant certified seed tubers and avoid fields with a history of corky ringspot. If fields have high populations of stubby root nematodes, fumigating with 1,3-dichloropropene* may be warranted.

* Permit required from county agricultural commissioner for purchase or use.



[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Potato
UC ANR Publication 3463
R. M. Davis, Plant Pathology, UC Davis
J. Nuñez, UC Cooperative Extension, Kern Co.
B. J. Aegerter, UC Cooperative Extension, San Joaquin Co.
Acknowledgment for contributions to the disease section:
C. Smart, Plant Pathology, UC Davis

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