Colonization of cereal and noncereal crop residues by Fusarium spp. in southeast Saskatchewan

In July of 2000 and 2001, residues of wheat, barley, oat, canola, flax, lentil and pea crops were sampled from over 300 fields in southeast Saskatchewan. The noncereal crops sampled had been preceded by a cereal crop, whereas the cereal crops sampled had been preceded in most cases by a noncereal crop the previous year, and by another cereal crop one to three years previously. Residues were surface-disinfested and plated on nutrient agar for fungal identification. The most commonly isolated Fusarium species was F. avenaceum. Among those at lower levels were F. acuminatum, F. equiseti, F. culmorum and F. graminearum. Based on total fungal isolations, the relative percent isolation of most Fusarium spp. was similar for all residue types. However, the actual percent isolation of Fusarium spp. from canola residues was lower than from the other residue types. F. avenaceum was found at the highest levels in lentil, pea and flax residues. All Fusarium spp. found in/on residues were also previously isolated from wheat and barley heads affected by fusarium head blight (FHB) in Saskatchewan, although at different relative frequencies. Colonization of canola, flax, lentil and pea residues by Fusarium spp. commonly associated with FHB and root rot of cereals suggests that rotations with these noncereal crops might not be an effective control strategy against cereal diseases caused by Fusarium spp. in Saskatchewan. This is the first report of isolation of F. graminearum from residues of the most commonly-grown noncereal crops in western Canada.