During 2002, two nurseries in southeastern Virginia reported losses exceeding 75% of container-grown inkberry holly (Ilex glabra) cv. Shamrock. The development of necrotic leaf spots and blotches followed initial symptoms of leaf yellowing and wilting. Affected leaves rapidly turned brown and fell. Dark brown-to-black roots were washed and plated on agar media. Phytophthora cinnamomi Rands was consistently isolated and identified on the basis of its morphology (2) and single-stranded conformational polymorphism fingerprint (1). The organism had nonpapillate, internally proliferating, noncaducous, ovoid to ellipsoid sporangia that formed only in water. It did not grow at 35°C and had abundant botryose hyphal swellings, coralloid hyphae, and grape-like clusters of chlamydospores. The isolate, determined to be the A2 mating type, produced elongate cylindrical, amphigynous antheridia and oogonia with a tapered base. A pine bark potting mix amended with V8 juicetreated vermiculite colonized by the suspected pathogen was placed in 12-liter containers. Two inkberry holly cv. Shamrock liners were planted in each of three containers and two 1-yr-old plants were planted in each of three additional containers during April 2004. An identical set of six containers of noninoculated plants was also established. During June 2004, inoculated plants exhibited symptoms identical to those observed in nurseries, and P. cinnamomi was isolated. Noninoculated check plants did not develop symptoms. Japanese holly (I. crenata) was previously known as a host, but to our knowledge, this is the first report of inkberry holly (I. glabra) susceptibility.
References: (1) P. Kong et al. Fungal Genet. Biol. 39:238, 2003. (2) D. J. Stamps et al. Mycol. Pap. No. 162. CAB International Mycological Institute, Wallingford, UK, 1990.