WINDBORNE DISPERSAL OF COLLETOTRICHUM-TRUNCATUM AND SURVIVAL IN INFESTED LENTIL DEBRIS

Different windborne materials were examined as potential sources of in oculum of Colletotrichum truncatum, the cause of anthracnose of lentil . Dust generated during harvest of anthracnose-infested lentil crops w as 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 w inds in the fall from fields with infested lentil stubble also were so urces of inoculum. Infectivity of dust, debris, and soil samples was d etermined by inoculating lentil assay plants. Samples that had overwin tered outside also caused anthracnose on inoculated assay plants. Micr osclerotia 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 inoc ulum for subsequent lentil crops planted at a distance. Dispersal of C . truncatum by wind has likely contributed to the spread of lentil ant hracnose in western Canada. C. truncatum forms microsclerotia on infec ted lentil plants. A 4-year survival study of the pathogen showed that infectivity of infested debris placed on the soil surface declined du ring the first 12 months of exposure, whereas infectivity of buried de bris remained high, until a rapid decline occurred at 48 months. The l ong-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 infectio n.