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 high mortality of chestnut trees in central Italy. Phytophthora cambivora was isolated from 11·6% of the soil samples taken around symptomatic trees, and was mainly associated with heavily diseased trees. It was the most aggressive species to Castanea sativa , but survived poorly in the soil. Phytophthora citricola and P. cactorum showed a limited ability to induce disease on chestnut, but could be recovered from soil during most of the year. A fourth species, P. gonapodyides , was recovered only from mud of stream beds within the chestnut stands. Involvement of these species in the development of disease is discussed.