Potato mop-top virus: knowledge review, and evaluation of the biosecurity response to ‘incursion’ of this virus in New Zealand

Pomovirus solani (common name: potato mop-top virus, PMTV) was first recorded in New Zealand on 11 September 2018. In contrast, Spongospora subterranea, the vector of PMTV, was first recorded in New Zealand in 1909, and is widespread causing important diseases of potato. PMTV causes distortion on potato leaves, shoots and tubers, and was designated at the time of first record as an Unwanted Organism by the New Zealand Ministry for Primary Industries. Spongospora subterranea and PMTV can survive for long periods in soil and in alternative hosts, so multi-year non-potato crop rotations are important for limiting the diseases caused by these pathogens. Both pathogens can also survive in wastes from potato processing factories, so disposal of processing effluent should be avoided on paddocks likely to be used for potato crops. The first observation and timely reporting of PMTV symptoms by a potato processing company instigated an official biosecurity response to the virus ‘incursion’, although PMTV may have been present 1 or 2 years prior to this first record. Rapid establishment of a PMTV Technical Advisory Group, including relevant international expertise, and the advice it provided, effectively directed the prompt response to the PMTV ‘incursion’, and the Ministry for Primary Industries and Potatoes New Zealand (Inc.) swiftly and effectively developed capability for monitoring and management of the ‘incursion’. Efforts since then by the New Zealand potato industry have reduced potential impacts of PMTV in this country, as demonstrated by low incidence of the virus in seed potato crops in 2019/20 and 2020/21. This low incidence indicates that PMTV is not adversely affecting potato productivity in New Zealand, and that management of the virus ‘incursion’ has been effective.