Incidence and severity of leaf-spotting diseases of spring wheat in Southern Manitoba
1998
Gilbert, J. | Woods, S.M. | Tekauz, A. (Agriculture and Agri-Food Canada, Winnipeg (Canada). Cereal Research Centre)
From 1989 to 1993, annual surveys were carried out to monitor incidence and severity of septoria nodorum blotch (SNB), tan spot, and spot blotch. Between 123-185 fields of bread, Canada Prairie Spring (CPS), and durum wheat types were surveyed each year. Infected leaf tissue was collected, surface sterilized, and placed in moisture chambers for 5-7 days to facilitate disease identification based on conidiation of pathogenic species. Environmental data were collected from the weather station closest to each field. In durum wheat, incidence and severity of SNB were lower, and of tan spot higher, than in the other two wheat types. Incidence of spot blotch was similar in all classes, but severity was higher in CPS wheat than in the other two wheat types. All wheat types showed a positive correlation between. Spot blotch severity and minimum and maximum temperatures, and a negative correlation for tan spot severity and amount of rainfall. Higher levels of SNB were associated with lower temperatures and with rain. In part, the environmental data help to explain the variability in annual incidence and severity of leaf-spotting diseases of wheat in Manitoba. A study to monitor these disease levels in conventional and conservation tilled fields was initiated in Manitoba in 1993. Infected leaf tissue was collected at growth stages (GS) 39, 65, and 75. Variation between years was highly significant for all diseases except spot blotch. Tan spot and septoria diseases increased as plants matured, but spot blotch was most severe at GS 61 and least at GS 39. Effect of tillage system on disease levels was not significant in this study.
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