PMTV

PMTV originated from the Andean region of South America and has been reported in Canada and several U.S. states, including Maine, North Dakota, Washington, Idaho, New Mexico and Colorado. It is also found in the United Kingdom, Ireland, Great Britain and the Nordic countries in Asian countries in Japan and China.

Biology

PMTV belongs to the genus Pomovirus within the family Virgaviridae. The virus has three single-stranded RNA segments. RNA1 encodes RNA-dependent RNA polymerase, RNA2 contains the coat protein (CP) and RNA3 harbors a triple gene block (TGB) which facilitates cell-to-cell and systemic movement. PMTV is transmitted by a soilborne protozoan called Spongospora subterranea f. sp. subterranea (Sss), which also causes powdery scab in potatoes. The virus can persist in the soil for up to 18 years within the resting spores of its vector.

Symptoms

The most notable symptom is tuber necrosis, characterized by dark brown, necrotic arcs or lines within the tuber flesh, commonly referred to as "spraing." PMTV rarely causes symptoms on the leaves.

Damage

Infected plants show reduced yields and tuber quality, significantly impacting potato production.

Management

Managing PMTV involves rotating potatoes with non-host crops to reduce virus and vector buildup, avoiding over-irrigation to prevent the vector Spongospora subterranea from thriving, and maintaining sanitation by cleaning equipment and avoiding soil movement from infected fields. Controlling the vector includes using certified seed potatoes free from powdery scab and applying soil treatments judiciously. Soil testing and certified seed help manage PMTV by detecting the virus’s soilborne vector and preventing the introduction of infected planting material. Additionally, planting resistant potato varieties, as recommended by research and extension services, is crucial for effective management.

References

• Duellman, K., Woodhall, J. Karasev, A. Olsen, N. and Whitworth J. 2022. Potato Mop-Top Virus: Biology and Disease Management. University of Idaho Extension Bulletin No 1017
• Stevenson, W.R., Loria, R., Franc, G.D. and Weingartner, D.P. 2001.Compendium of Potato Diseases, 2nd Edition. St. Paul, Minnesota, APS Press.

Pesticide Warning

Always read and follow the instructions printed on the pesticide label. The pesticide recommendations in this University of Idaho webpage do not substitute for instructions on the label. Pesticide laws and labels change frequently and may have changed since this publication was written. Some pesticides may have been withdrawn or had certain uses prohibited. Use pesticides with care. Do not use a pesticide unless the specific plant, animal or other application site is specifically listed on the label. Store pesticides in their original containers and keep them out of the reach of children, pets and livestock.

Trade Names — To simplify information, trade names have been used. No endorsement of named products is intended nor is criticism implied of similar products not mentioned.

Groundwater — To protect groundwater, when there is a choice of pesticides, the applicator should use the product least likely to leach.

Christian Cumagun, Plant Pathologist
James Woodhall, Plant Pathologist, Associate Professor and Extension Specialist
2025