Steveninck and Cruickshank (1956) stated that the widespread incidence of linseed diseases such as rust, and to a limited extent pasmo (Mycosphaerella linorum) added to the instability of the crop; in the 1952-53 season pasmo occurred at an epidemic level in mid and south Canterbury in crops of the variety `Golden Viking'; selections were made for disease resistance and the varieties `Bison' and `Very Pale Blue Crimped' were shown to be resistant. Sanderson (1963) showed that seed transmission was a minor factor in the spread of the disease in New Zealand. The fungus overwintered on the common perennial introduced wild species Linum marginale as well as any debris of L. usitatissinum from previous seasons crops. Ascospores from perithecia formed on old stems of L. marginale were shown to be important in the establishment of the initial infection of the disease into the crop.