In 1949, Thung was approached by the Ministry of Agriculture in The Hague, asking him whether he was interested in the position of Head of the Virology Department of the newly established Instituut voor Plantenziektenkundig Onderzoek (Institute for Phytopathological Research, IPO) in Wageningen. In addition to head of the IPO Virology Department, Thung was also offered a chair by special appointment at the Agricultural College, making him the world’s first professor of Virology.

His position as head of the IPO Virology Department and as professor of Virology marked the start of an entirely new phase in Thung’s scientific career. The focus shifted from doing research to a role as leader and initiator.