AN EPIDEMIOLOGIC-STUDY OF PUCCINIA-PUNCTIFORMIS (STR) ROHL AS A STEPPING-STONE TO THE BIOLOGICAL-CONTROL OF CIRSIUM-ARVENSE (L) SCOP

The infection cycle of the autoecious rust fungus Puccinia punctiformi s on the clonal plant Cirsium arvense was described in terms of intens ity (amount of pathogen per unit area and used for systemic infection) and extent (area occupied by the pathogen and used for local lesion i nfection) at four grassland sites in The Netherlands. The incidence of systemic infection was relatively low and systemically infected shoot s were typically concentrated at a few locations within a site. Incide nce of local lesion infection was relatively high and widespread in al l sites. Spatial and temporal distribution of teliospores, the inoculu m for systemic infection, were quantified in order to explain the rela tively low and spatially unequal incidence of systemic infection. Beca use of the large impact of systemic infection on C. arvense shoots, it is concluded that st spatially homogeneous distribution of teliospore s may be a prerequisite for the biological control of C. arvense by P. punctiformis.