Sporulation of Bipolaris sorokiniana on the crowns of crop plants grown in Saskatchewan

Production of conidia by B. sorokiniana was determined on crowns of field-grown annual crops in the fall of each year from 1991 to 1993. Sporulation was highest on crowns of the annual cereal crops, barley, canary seed, rye, triticale, oat, and wheat. Sporulation varied from year to year with the highest numbers in 1992 and the lowest in 1993. There were differences between cultivars of wheat and of barley, but the differences were not consistent from year to year. Significantly lower conidial numbers occurred on annual pulse crops (fababean, field pea, lentil), and oilseed crops (canola, flax, mustard, safflower, sunflower) than on cereal crops. In 1992 and 1993, sporulation was assessed on perennial forage legumes and grasses. Sporulation was significantly higher on wheatgrass species (crested, intermediate, northern, slender, streambank, tall, and western wheatgrass) than on other forage grasses (smooth bromegrass, meadow bromegrass, reed canarygrass, Altai wildrye, Dahurian Wildrye, and Russian wildrye) and forage legumes (alfalfa, alsike clover, birdsfoot trefoil, cicer milkvetch, red clover and sainfoin). The low sporulation on crowns of annual pulse crops, annual oilseed crops, forage legumes, and forage grasses other than on wheatgrass species indicates their suitability in crop rotations designed to reduce the inoculum density of B. sorokiniana. Growing annual cereal crops and wheatgrass forage grasses will likely maintain or increase the inoculum levels of B. sorokiniana in soil.