Recovery and pathogenicity of Phytophthora species associated with a resurgence of ink disease in Castanea sativa in Italy

Three species of Phytophthora, P. cambivora, P. citricola and P. cactorum, were found to be associated with a recent outbreak of ink disease causing h igh mortality of chestnut trees in central Italy. Phytophthora cambivora wa s isolated from 11.6% of the soil samples taken around symptomatic trees, a nd was mainly associated with heavily diseased trees. It was the most aggre ssive species to Castanea sativa, but survived poorly in the soil. Phytopht hora citricola and P. cactorum showed a limited ability to induce disease o n chestnut, but could be recovered from soil during most of the year. A fou rth species, P. gonapodyides, was recovered only from mud of stream beds wi thin the chestnut stands. Involvement of these species in the development o f disease is discussed.