Potato Mop-Top Virus
Potato mop-top virus (PMTV)
1 host plant · Viral
Last updated
This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.
Potato Mop-Top Virus can show up on landscape plants, producing visible damage that ranges from leaf spots and discoloration to branch dieback depending on severity. Early detection gives you the best management options.
Start with sanitation: remove and dispose of affected material as you find it. Thin dense growth to improve air circulation, and redirect irrigation away from foliage. If the condition persists despite cultural adjustments, your local Extension office can help identify the pathogen and recommend targeted treatments.
Quick Reference
Management
The critical infection window is early in tuber development (3-4 weeks post-emergence) when developing stolons and tuber primordia are most susceptible to S. subterranea penetration. Infection can occur throughout the growing season but early infection typically results in higher tuber virus loads. Tubers accumulate virus until harvest. All potato plants grown in Spongospora-infested soil are vulnerable. Once soil is contaminated, fields remain infested for 18+ years.
Foliar symptoms develop 4-6 weeks post-emergence on infected plants, appearing as chlorosis, mottle, and stunting. In North America, tuber symptoms predominate: hollow necrotic spots inside tubers ('mop-top' appearance). In Europe, dark brown necrotic arcs discolor tuber flesh. Symptom severity depends on virus strain, plant variety, and infection timing. Cool, moist growing seasons enhance symptom development. Symptom-bearing plants produce high percentages of infected offspring tubers even when above-ground symptoms are absent.
Cultural Controls
- Use certified PMTV-tested seed potatoes from Spongospora-free sources. Avoid planting in fields known to be infested with Spongospora subterranea (soil remains infested for 18+ years). Practice field rotation away from potatoes for as long as feasible in infested areas. Clean and disinfect equipment between fields to prevent contaminated soil movement. Avoid compacting soil during wet conditions that favor S. subterranea activity. Manage volunteer potatoes and solanaceous weeds that serve as disease hosts. Scout crops for foliar symptoms. Harvest infected tubers separately to prevent contaminating storage facilities. Source: Wikipedia; PNW Plant Disease Management Handbook