Problem Statement: Each year some consignments of buttercup squash from New Zealand, worth about US$600,000 per year to growers, were being destroyed or reshipped by South Korea because of a fungus that was believed to threaten their domestic rice crop. Potatoes from USA have also been destroyed when the same fungus was detected. The Korean National Plant Quarantine Service had listed Verticillium tenerum in their Controlled Pathogen List as a Category 2 organism – “commodity allowed into country with proper treatment, or otherwise contaminated material to be destroyed or otherwise disposed.” New Zealand authorities had also listed this fungus as a quarantine pest on Pinus seed imports into New Zealand.

Methods: A thorough literature review and consultation with colleagues on the naming, biology, distribution, and pathogenicity of V. tenerum was undertaken to convince Korean authorities that this fungus is neither a parasite of rice nor a legitimate quarantine pest.

There has been extensive confusion over the naming of the fungus known as V. tenerum and debate over whether or not it is the anamorph of Nectria inventa. The correct name for the fungus is V. luteo-album, and it is not related to N. inventa. Molecular and morphological studies (communicated by Dr W. Gams, Centraalbureau voor Schimmelcultures, Netherlands) have shown that V. luteo-album possibly belongs in a separate genus from the well-known plant pathogenic species, V. albo-atrum and V. dahliae. V. luteo-album is a cosmopolitan saprobe with no damaging effects on rice.

Outcomes and Impacts: Both the Korean and New Zealand authorities have now removed V. luteo-album from their pest lists after accepting the results of research that showed it was not a threat. New Zealand buttercup squash growers now have an assured market and Koreans have access to off-season, high quality squash.

Lessons: Taxonomic expertise and a thorough review of Verticillium luteo-album provided the evidence that quarantine authorities required to remove a non-tariff trade barrier.