First report of the white rust of spinach Wilsoniana occidentalis in Germany
The white rust of spinach Wilsoniana occidentalis is reported for the first time from Germany. It was identified in an open field of spinach (Spinacia oleracea) in Baden-Wurttemberg. This oomycete probably originates from North America but has been also recorded in China, India, Iran, Pakistan. In the EPPO region, it was first reported in Greece in 2013, Türkiye in 2018 and Italy in 2021. The host plants of W. occidentalis hosts belong to the Amaranthaceae and spinach is the only species grown commercially.
W. occidentalis is an important disease of spinach in the USA. The pathogen causes chlorotic spots on the leaf surface that develop and often coalesce. Damage reduces both spinach quality and yield and may reach total crop failure as heavily infested leaves are not marketable. The disease is usually controlled by fungicides and the use of less susceptible varieties.
W. occidentalis is not known to be seed-borne, but in the USA it has been recorded as a surface contaminant of seed produced in infested areas. Appropriate disinfection or hot water treatment of the seed will prevent such contamination.
An express PRA conducted by JKI concluded that this pathogen was presenting a high risk for Germany and the other EU countries and recommended measures to limit the spread of W. occidentalis in Germany.
Sources
JKI (2022) Express-PRA zu Wilsoniana occidentalis – Auftreten https://pra.eppo.int/pra/4cad026c-7144-4516-a59f-da44a1ab8fb9