Phytophthora ramorum infects hazelnut, vine maple, blue blossom, and manzanita species in California.

摘要

Symptomatic tissues of California hazelnut ( Corylus cornuta var. californica), vine maple ( Acer circinatum), blue blossom ( Ceanothus thyrsiflorus), and two species of manzanita ( Arctostaphylos columbiana and Arctostaphylos manzanita) were observed in the spring of 2006 in California, USA. Field symptoms on hazelnut included leaf water-soaking and marginal necrosis. The infection apparently spread into young stems, causing shoot dieback. Vine maple exhibited petiole necrosis. Blue blossom and both Arctostaphylos species displayed leaf spots and stem lesions. Shoot dieback was observed in naturally infected blue blossom plants. Association of symptomatic tissues with Phytophthora ramorum was confirmed by plating on PARP agar. Each isolate was tested for pathogenicity on its corresponding host. Phytophthora ramorum was re-isolated from symptomatic tissues of all inoculated shoots but not from control shoots. This is thought to be the first report of these plant species as natural hosts of Phytophthora ramorum.