Ophiostomatales isolated from two European bark beetles, <i>Hylurgus ligniperda</i> and <i>Orthotomicus erosus</i>, in California

Kim, Sujin
Major Professor
Harrington C. Thomas
Committee Member
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Plant Pathology and Microbiology

Two European pine-infesting bark beetles, Hylurgus ligniperda and Orthotomicus erosus, were first detected in July 2003 in Los Angeles, California and in May 2004 in the Central Valley of California, respectively. These bark beetles (Coleoptera: Curculionidae: Scolytinae) are common vectors of fungi in the Ophiostomatales, some of which are tree pathogens or causal agents of blue stain of conifer sapwood. Ophiostomatales were isolated on a cycloheximide-amended medium, which is semi-selective for the growth of Ophiostoma and related genera. In total, eight identified species and seven unidentified species of Ophiostomatales were isolated from 118 adults of H. ligniperda collected from infested pine logs at two sites in California. In the case of H. ligniperda, Ophiostoma ips and Grosmannia galeiforme were isolated from 31% and 23% of the 118 beetles, respectively. The other species isolated included O. piceae (isolated from 9% of the beetles), O. querci (8%), and a new species that will be described as Leptographium tereforme (6%). Grosmannia huntii, L. serpens, three Sporothrix spp., O. floccosum, O. stenoceras, two unidentified Hyalorhinocladiella spp., and a sterile fungus were each isolated from less than 5% of the beetles. In contrast, one identified species and four unidentified species of Ophiostomatales were isolated from 202 adults of O. erosus collected from infested pines at four sits in California. Ophiostoma ips was isolated from 85% of the 202 adults of O. erosus. Beside O. ips, a sterile fungus was isolated with 16% frequency, and two Sporothrix spp. and a species of Hyalorhinocladiella were isolated with fewer than 3% of the O. erosus. Most of the identified species were previously known in the USA and have been found in association with H. ligniperda or O. erosus in other countries. However, the new species, tentatively named L. tereforme, and G. galeiforme were recorded from the USA for the first time, and this is the first report of L. serpens from western North America.