Dieback and Mortality of Pines radiata Trees in Italy Associated with Phytophthora cryptogea.

Pinus radiata D. Don is a forest tree species native to the Monterey Baja in California. Due to its rapid growth and desirable lumber and pulp qualities, between 1960 and 1980, about 12,000 ha of P. radiata were planted in Sardinia, Italy. The only disease reported on this conifer species has been Diplodia pinea, which causes tip and branch dieback (3). In January 2012, dieback and mortality of 25-year-old radiata pine trees were observed in a reforestation area of about 20 ha located in northern Sardinia (40°43′N, 9°22′E, 600 m a.s.l.). Symptoms included chlorosis, reddish-brown discoloration of the whole crown or dieback starting in the upper crown and progressing downward through the crown, and necrotic bark tissues at root collar. Approximately 25% of the trees were affected. In a first attempt, a Phytophthora species was consistently isolated from the rhizosphere of 23 symptomatic trees, which included necrotic fine roots using oak leaves as bait (4). Afterwards, it was also isola...