Estimation of the Distribution of <i>Verticillium</i> Populations in Infected Strawberry Plants and Soil

Abstract

SUMMARY A rapid dilution‐plate technique has been evolved for the quantitative assay of the inoculum density of Verticillium spp. in infected plant tissues and in soil. Results showed a very high level of the pathogen (1,500 propagules/g soil) in the top 10 cm of soil from a severely‐infested strawberry site with the counts decreasing at lower depths. The top 30 cm of soil contained 98 per cent of the total estimated population. Abundant Verticillium inoculum was present in all vegetative tissues of infected plants with the exception of fruit stalks, the highest counts being recorded in root extracts. The relatively high inoculum level of the pathogen in stolon extracts demonstrates one method by which young runners may become infected.