XVI International Botanical Congess

In order to select aggressive fungal endophytes for use as mycoherbicides for the weeds purple nutsedge (Cyperus rotundus) and Canadian thistle (Cirsium arvense), endophytes were isolated from the two hosts and screened for pathogenicity. Whereas some of the isolates caused severe disease symptoms in the leaf segment tests, massive inoculations of the most effective isolates from the leaf segment tests on whole plants only caused small necrotic lesions or were asymptomatic. Thus, on the basis of our results we conclude that single infections with fungal endophytes are not sufficient for biocontrol of these weeds. First investigations with dual infections of endophytes and plant pathogens on purple nutsedge in glasshouse experiments suggest that the development of such a mycoherbicide is more promising.