It also overwinters in the soil on infected flax stubble. Spores, dispersed by wind and rain, cause the initial infections on leaves and stems. It attacks above-ground parts of the plant. The disease is more common in Manitoba with its moist climate than in the drier production areas of Alberta and Saskatchewan. Although flax is most susceptible to pasmo in the ripening stage, it can occur early in the season when warm, moist conditions prevail.
Lodging favours the development of pasmo, because of increased humidity within the crop canopy.
This leads to patches of dead plants completely covered with the fungus. Symptoms of Damage Pasmo is characterized by circular, brown lesions on the leaves and by brown to black infected bands that encircle the stem. These bands alternate with green, healthy bands, making pasmo easy to identify. Flowers and young bolls are also blighted. Older bolls are discoloured and contain shrivelled or non-viable seed.