Warfield C Y, Hwang J, Benson D M
Department of Plant Pathology, North Carolina State University, Raleigh 27695.
Plant Dis. 2008 Mar;92(3):474-481. doi: 10.1094/PDIS-92-3-0474.
A survey of 14 nurseries growing hybrid rhododendron, Pieris spp., or Viburnum spp. was conducted as part of the 2003 Sudden Oak Death Pilot National Survey to determine if Phytophthora ramorum, the causal agent of sudden oak death, had been introduced to nurseries in North Carolina. Over 220,000 hybrid rhododendrons, 1,700 plants of Pieris spp., and 2,800 plants of Viburnum spp. were surveyed. Across nurseries, blight and dieback incidence averaged 2.4% for Pieris spp. and 10% for rhododendron. P. ramorum was not recovered by isolation or detected by polymerase chain reaction in the 347 plant samples collected. Three species of Phytophthora were isolated from hybrid rhododendron and Pieris spp., but no Phytophthora isolates were recovered from Viburnum spp. P. citricola and P. cambivora were isolated most frequently (61 and 39 isolates, respectively), while 2 isolates of P. cactorum were recovered. Occasionally, two Phytophthora spp. were found in the same block of rhododendrons within a nursery, but only one species was recovered from an individual plant. Most cultivars of rhododendron surveyed, including 'English Roseum,' 'Nova Zembla,' and 'Roseum Elegans,' had less than 0.5% incidence of Phytophthora blight and dieback, whereas 'Lee's Dark Purple' had 3.8% disease incidence across all nurseries surveyed.
作为2003年橡树猝死试点全国调查的一部分，对14家种植杂交杜鹃花、马醉木属植物或荚蒾属植物的苗圃进行了调查，以确定橡树猝死的病原体——樟疫霉是否已传入北卡罗来纳州的苗圃。共调查了超过22万株杂交杜鹃花、1700株马醉木属植物和2800株荚蒾属植物。在各个苗圃中，马醉木属植物的枯萎病和枝枯病发病率平均为2.4%，杜鹃花的发病率为10%。在所采集的347个植物样本中，未通过分离培养获得樟疫霉，也未通过聚合酶链反应检测到该菌。从杂交杜鹃花和马醉木属植物中分离出了三种疫霉，但未从荚蒾属植物中分离到疫霉。柑橘疫霉和栎疫霉分离频率最高（分别为61株和39株），同时还分离到2株恶疫霉。偶尔，在一个苗圃的同一杜鹃花地块中发现了两种疫霉，但从单株植物中仅分离到一种。所调查的大多数杜鹃花品种，包括“英国玫瑰红”、“新泽西”和“优雅玫瑰红”，疫霉枯萎病和枝枯病的发病率均低于0.5%，而“李氏深紫”在所有调查苗圃中的发病率为3.8%。
