Symptoms and Signs
Aboveground symptoms of corky ringspot rarely occur. Symptoms in tubers vary depending on virus strain, potato variety, temperature, and time of infection. Symptoms of tubers can occur both externally or internally depending on cultivar. Arcs of discolored tissue can be seen on tuber surfaces; particularly on smooth skin cultivars, though internal symptoms are more common. Internal symptoms can be small flecks, necrotic rings, or large necrotic/corky areas in tubers. Internal flecks can be confused with alfalfa mosaic virus.
Comments on the Disease
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.
Management
Plant certified seed tubers and avoid fields with a history of corky ringspot. If planting in fields with history of corky ringspot and high numbers of stubby root nematodes, fumigation may be warranted to prevent severe damage.
| Common name | Amount per acre** | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| A. | 1,3-DICHLOROPROPENE*§ | |||
| (Telone) | Label rates | See label | NA | |
| B. | METAM SODIUM*§ | |||
| (Vapam) | 37.5–75 gal | See label | NA | |
| C. | METAM POTASSIUM*§ | |||
| (K-Pam) | Label rates | See label | NA | |
| NA | Not applicable |
| * | Permit required from county agricultural commissioner for purchase or use. |
| § | Do not exceed the maximum rates allowed under the California Code of Regulations Restricted Materials Use Requirements, which may be lower than maximum label rates. |