EFFECTS OF FUNGICIDE APPLICATIONS ON PASMO, YIELD AND FIBRE IN SEVERAL FLAX CULTIVARS

K. Y. Rashid¹ and S. Halley²

Pasmo caused by the fungus Septoria linicola (Speg.) Garassini (Sexual state Mycosphaerella linorum Naumov) is a common disease affecting flax (Linum usitatissimum L.) in all flax growing areas in North America. This disease is stubble-borne and starts as dark brown to black lesions on lower leaves with abundant pycnidia.  The wind and rain splash conidia from the lower leaves onto upper plant canopy and to adjacent plants. The fungus infects all above ground plant parts forming bands of brown discoloration on stems.  Severe epidemics occur when the disease infection starts early in the season and are favored by warm weather with sporadic rain showers throughout the growing season, and thick canopy.  Pasmo was prevalent in 62-96% of the fields surveyed between 1996 and 2007 (1, 2, 3), with mean disease incidence ranging from 16 % to 35% infected plants and mean disease severity ranging from 10% to 25% stem and leaf area affected (Table 1).  Commercial flax cultivars lack acceptable level of resistance to this pathogen; however, cultivars differ in their susceptibility to this pathogen.  The objectives of this study were to investigate the effects of the fungicide pyraclostrobin (Headline) on reducing the pasmo disease and its effects on seed and fiber yield in flax.