Pacific Northwest 1998 An Online Guide to Plant Disease Control

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OSU Extension Office
 
Potato (Solanum tuberosum) -- Potato Mop Top Virus
See Also: Potato -- Powdery Scab
 
Cause: The Potato mop top virus (PMTV) is a pomovirus vectored by the fungus Spongospora subterrenea, which causes powdery scab of potato (see Potato—Powdery Scab). The virus can be found in scab spore-balls and can remain viable in the field up to 18 years without the host. PMTV can also be tuberborne.

Until 2001, PTMV was considered an exotic pathogen, found primarily in cooler growing regions around the world. It was detected in a few lots of processing potatoes from Idaho, Oregon, and Washington in 2001 but not in 2002. Yield losses can be up to 20% in highly sensitive cultivars.

Symptoms: Symptoms of PMTV vary depending on cultivar and environmental conditions. Foliar symptoms may include yellow rings, V shape markings, and blotches, especially on the lower leaves. Stems may also be stunted, giving a “mop top” effect. Secondary infections may lead to parallel necrotic rings or arcs and cracking inside the tuber. These rings may not be present at harvest but may develop during storage. It can be confused with corky ringspot and diagnostic tests are usually needed to determine whether PMTV is present.
Cultural control:
  1. Plant only certified potato seed.
  2. Keep powdery scab under control.
  3. Do not move contaminated soil or equipment into clean fields.
  4. Genetic resistance has not been identified in commercial lines.
Content edited by: Cynthia M. Ocamb on January 1, 2009
 
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