Water as the source of Phytophthora spp. pathogens for horticultural plants.

Using rhododendron leaf blades, Phytophthora spp. was recovered from 4 rivers, 3 reservoirs and 3 canals located in different parts of Poland. Independently of water sources location, P. citricola was found in rivers, reservoirs and canals. Detection period and different sources of water had no big influence on Phytophthora spp. population density. Occurrence of P. cactorum, P. cambivora and P. cinnamomi in sampling water was influenced by presence of potential host plants near river and in nurseries. Under conditions favourable to the development of Phytophthora spp., P. citricola dispersed with sprinkling water in 2 hardy ornamental nursery stocks, caused shoot and tip blight of boxwood and thuja. [ABSTRACT FROM AUTHOR]