01926nas a2200169 4500008004100000245011900041210006900160300001200229490000700241520135400248100001501602700001801617700001801635700001901653700001501672856006901687 2002 eng d00aPhytophthora ramorum as the cause of extensive mortality of Quercus spp. and Lithocarpus densiflorus in California0 aPhytophthora ramorum as the cause of extensive mortality of Quer a205-2140 v863 a

A new canker disease, commonly known as sudden oak death, of Lithocarpus densiflorus, Quercus agrifolia, Q. kelloggii, and Q. parvula var. shrevei in California is shown to be caused by Phytophthora ramorum. The pathogen is a recently described species that previously was known only from Germany and the Netherlands on Rhododendron spp. and a Viburnum sp. This disease has reached epidemic proportions in forests along approximately 300 km of the central coast of California. The most consistent and diagnostic symptoms on trees are cankers that develop before foliage symptoms become evident. Cankers have brown or black discolored outer bark and seep dark red sap. Cankers occur on the trunk at the root crown up to 20 m above the ground, but do not enlarge below the soil line into the roots. Individual cankers are delimited by thin black lines in the inner bark and can be over 2 m in length. In L. densiflorus saplings, P. ramorum was isolated from branches as small as 5 mm in diameter. L. densiflorus and Q. agrifolia were inoculated with P. ramorum in the field and greenhouse, and symptoms similar to those of naturally infected trees developed. The pathogen was reisolated from the inoculated plants, which confirmed pathogenicity.

1 aRizzo, D M1 aGarbelotto, M1 aDavidson, J M1 aSlaughter, G W1 aKoike, S T uhttp://apsjournals.apsnet.org/doi/abs/10.1094/PDIS.2002.86.3.205