BUSINESS potato mop-top virus

Potato mop-top virus (PMTV) is found in most potato-growing regions worldwide, with the virus recently detected for the first time in Australia in Tasmania. There have been no detections of the virus in Western Australia.

Words Marcus Visic, Plant Biosecurity Communications Manager, Biosecurity and Emergency Management, DPIRD

Photography William M. Brown Jr.

What is potato mop-top virus?

PMTV is a plant virus (Pomovirus solani) that can affect developing potato plants, damaging their leaves, shoots and tubers, reduce the quality of the tuber flesh, and impact crop yield in some potato varieties.

The disease is established in North America and Europe and when managed effectively results in minimal production losses. The virus was detected in New Zealand in 2018, where it requires ongoing management. There are no food safety or human health risks associated with the virus and potatoes are safe to consume.

How does it survive and spread?

The virus is spread by Spongospora subterranea, a soil-borne pathogen that causes powdery scab in potatoes. Powdery scab is common in Tasmania and mainland Australia, including Western Australia.

The virus can also be passed on to daughter plants if the mother tuber used for propagation was infected.

While the main host of PMTV is potato, the weeds black nightshade (Solanum nigrum) and white goosefoot (Chenopodium album) can sometimes be infected.

PMTV is highly persistent, surviving up to 18 years inside powdery scab spores — even without host plants.

While there is no way to eliminate this virus-pathogen complex, it can be managed through strong biosecurity and crop rotation. The disease can spread through infected seed tubers, soil on boots, machinery and potato waste.

What to look for

• Slightly raised lines and rings on the surface of potato tubers

• Misshapen tubers

• Brown flecks, arcs or lines inside the tubers

• Yellow blotches or ‘v’ shaped chevrons on the leaves, distortion of leaflets or shortening of internodes causing a dwarfed appearance (mop-top)

• There may not be any leaf symptoms

Detection in Australia

In July 2025, PMTV was detected in potato tubers originating from a property in northwest Tasmania. The detection was a result of a grower reporting suspected viral symptoms in infected potatoes.

Biosecurity Tasmania undertook tracing activities with surveillance efforts identifying several properties linked to PMTV detections, and investigations indicating it may have been present in the state for at least 2 years. The virus has been detected in several potato varieties grown in Tasmania.

On 19 September 2025, the Australian, state and territory governments, and affected industry agreed that it was not technically feasible to eradicate PMTV from Australia. The decision reflected several challenges including:

• Difficulty detecting all infected areas

• The virus’s ability to persist undetected in soil

• Widespread presence of powdery scab (a known vector)

• Risk of spread via seed, tubers and soil movement

Following the detection, Western Australia, Victoria, South Australia and New South Wales introduced biosecurity requirements for potatoes and other host products to manage the risk of the virus spreading to the mainland.

Protect what you’ve built — and WA’s clean reputation

Although PMTV has not been detected in WA, growers can take steps now to protect their farms.

Most growers already have good on-farm biosecurity practices like cleaning tools, keeping records or knowing who has been on their farm. Good biosecurity is less about extra tasks and more about protection — it is insurance for the hard work you have already put in.

Every action counts, not just for preventing PMTV but other plant pests and diseases. Simple steps you can take include:

• A dedicated high-pressure washdown station

• Clean clothing, boots, tools, equipment and machinery before and after use in production areas

• Limit the movement of people and contractor vehicles within production areas and paddocks whenever possible

• Monitor crops and report anything suspect.

Strong biosecurity ensures we can continue growing high-quality marketable produce and access valuable export markets.

MORE INFORMATION

Visit www.dpird.wa.gov.au/pmtv