Can Phytophthora ramorum be spread with Contaminated Irrigation Water

In a two year study, the spread of Phytophthora ramorum with contaminated irrigation water and the survival of the pathogen in water reservoirs were studied (Werres and others 2007). In addition at the end of each experimental period root ball samples from asymptomatic plants were taken to look for contamination with P. ramorum. For the study, an open air simulation system with nine separate container stands was used. The surplus water from each container stand ran back to a separate water basin. From the water basins, the water was taken for overhead irrigation of the plants on the container stands. In both years rooted Rhododendron cuttings of the cv ?Cunningham?s White?, in the second year also Viburnum plicatum cv 'Mariesii' were placed on the container areas and irrigated from above with water taken from the water reservoirs. The reservoirs were inoculated once a year in June with two different inoculum concentrations (low inoculum density: 12.5 Petri dishes per reservoir = 1000 L, high inoculum density: 25 Petri dishes per reservoir in 2004 and 50 in 2005). Three reservoirs were not inoculated.