Windborne dispersal of Colletotrichum truncatum and survival in infested lentil debris

Different windborne materials were examined as potential sources of inoculum of Colletotrichum truncatum, the cause of anthracnose of lentil. Dust generated during harvest of anthracnose-infested lentil crops was shown to be a source of inoculum that could be dispersed by wind at least 240 m from a combine. Plant debris and soil dispersed by high winds in the fall from fields with infested lentil stubble also were sources of inoculum. Infectivity of dust, debris, and soil samples was determined by inoculating lentil assay plants. Samples that had overwintered outside also caused anthracnose on inoculated assay plants. Microsclerotia were on windborne lentil debris, but it was not possible to identify C. truncatum microscopically in the collected dust and soil samples. It appears that diseased lentil crops can be a source of inoculum for subsequent lentil crops planted at a distance. Dispersal of C. truncatum by wind has likely contributed to the spread of lentil anthracnose in western Canada. C. truncatum forms microsclerotia on infected lentil plants. A 4-year survival study of the pathogen showed that infectivity of infested debris placed on the soil surface declined during the first 12 months of exposure, whereas infectivity of buried debris remained high, until a rapid decline occurred at 48 months. The long-term survival of C. truncatum in buried lentil debris may explain the high level of infestation found in many fields in the province of Manitoba, although windborne inoculum may also be a source of infection.