Potato mop-top virus (PMTV) was recently detected in Northwest Tasmania – Australia’s first encounter with this plant pathogen. It’s a good reminder for New Zealand potato growers about the importance of continued vigilance against an existing but well-managed threat.
For New Zealand’s potato industry, PMTV is not new territory. The virus was first identified here in September 2018 when a potato processing factory spotted characteristic symptoms in tubersduring a load inspection.
New Zealand’s experience demonstrated that whilst complete eradication was impossible, effective long-term management was achievable. Through industry-led initiatives supported by Biosecurity New Zealand, PMTV has been maintained as a pathogen of low significance for local potato production.
The virus, which causes distortions in potato tubers including rust-coloured arcs, flesh cracking, and necrosis, poses no food safety risks to consumers. However, it can significantly affect processing quality and crop yields if left unmanaged. PMTV spreads through Spongospora subterranea, the soil-borne pathogen that causes powdery scab, and can remain viable in soil for over 12 years.
New Zealand’s success in managing PMTV stems from several key strategies. The industry implemented rigorous seed potato health procedures, developed comprehensive identification guides for growers, and established routine surveillance testing. Crucially, growers already practised long crop rotations and maintained awareness of powdery scab management, which naturally limited PMTV spread.
Canterbury, as New Zealand’s primary seed potato region, was initially most at risk of widespread dissemination. However, coordinated efforts between Potatoes New Zealand, the Ministry for Primary Industries, and processing companies like McCain Foods ensured rapid containment and management protocols.
Current surveillance shows PMTV continues to occur at very low incidence in harvested potatoes, particularly from processing crops. This demonstrates that whilst the virus remains present, effective management keeps it from becoming a significant threat to productivity or profitability.