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A decline of coast live oak (Quercus agrifolia) has been observed throughout southern California. In this study, the identity and pathogenicity of non-Botryosphaeriaceae fungal species consistently recovered from necrotic tissues of branch and bleeding trunk canker samples from these locations were assessed. Species were identified morphologically and by comparison of the complete sequence of the internal transcribed spacer (ITS) of the ribosomal DNA to sequences available in GenBank. Phylogenetic analyses were then conducted using ITS and partial sequences of the ß-tubulin and mitochondrial small ribosomal subunit genes for unknown species. Fungi recovered and identified included Fusarium solani, Phaeoacremonium mortoniae, Diatrypella verrucaeformis, and a fungus described herein as Cryptosporiopsis querciphila sp. nov. One-year-old coast live oak seedlings were wound inoculated under controlled conditions to test pathogenicity of the fungal species. Each fungal species was successfully reisolated from necrotic tissue at 70 and 100% for P. mortoniae and all other species, and xylem necrosis was significantly different between all treatments and controls (P < 0.0001 at α = 0.05). Isolates of F. solani were the most aggressive tested. These species represent new records of fungal pathogens of coast live oak in California. Results from the pathogenicity test suggest that these fungi play a role in the decline of southern California coast live oak trees.

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Symptoms of decline have been observed on dying coast live oak (Quercus agrifolia) trees in areas throughout southern California that are both infested and uninfested by the gold-spotted oak borer (GSOB). The purpose of this study was to identify and assess the pathogenicity of several anamorph species of the Botryosphaeriaceae, including Diplodia corticola, Dothiorella iberica and Diplodia agrifolia sp. nov., that were recovered consistently from symptomatic tissues. Species were identified morphologically and by phylogenetic analyses of the complete sequence of the internal transcribed spacer (ITS) of the rDNA and partial sequences of ß-tubulin and elongation factor (EF1-α) genes. Results from morphological assessments and phylogenetic analyses support the erection of a new species closely related to D. mutila, described herein as Diplodia agrifolia sp. nov. Pathogenicity of all species was verified by wound inoculation of 1 y old coast live oak seedlings under controlled conditions. Isolates of D. corticola were the most aggressive tested, and isolates of D. agrifolia were the second most aggressive. Both species caused bleeding symptoms on inoculated seedlings. Seedlings inoculated with D. corticola died within 4 wk, with the pathogen progressing up and down through the xylem in advance of living phloem and moving throughout the taproot in 70% of inoculated seedlings. Colonization and re-isolation was successful for all species. All three fungal species represent newly recorded fungal pathogens of coast live oak in California. Results from the pathogenicity test suggest that these fungi play a role in the decline of coast live oaks throughout southern California.

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Individual lodgepole pines (Pinus contorta) were fertilized with urea at nitrogen (N) inputs equivalent to 0, 315, or 630 kg/ha. Four months after application of the fertilizer, inner bark tissue N concentrations were significantly higher in the trees that had received the low dose (315 kg/ha) fertilization treatment than in the control trees; trees that had received the high-dose treatment (630 kg/ha) were intermediate and not significantly different from either of the other treatments. There was a significant positive correlation between N concentration in inner bark tissue and larval mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae, Scolytinae). In vitro studies on synthetic growth media examined effects of temperature and N concentration on N concentration of two common fungal associates of the mountain pine beetle (Ophiostoma clavigerum and Ophiostoma montium). Increasing N concentration in growth media significantly increased fungal N concentrations in both O. clavigerum and O. montium. Furthermore, N concentration was consistently higher in O. clavigerum than in O. montium. Neither species had sufficient growth at 30 degrees C, nor did O. clavigerum at 15 degrees C, to test N concentration. However, for O. montium, increasing temperatures decreased fungal N concentrations. There was no correlation between N concentration of O. clavigerum and growth temperature. Potential impacts of ingestion of the fungal species by developing mountain pine beetle larvae-infesting trees under various environmental conditions such as increasing temperatures are discussed.

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White pine blister rust, Cronartium ribicola, has plagued the forests of North America for almost a century. Over past decades, eastern white pine (Pinus strobus) that appear to tolerate the disease have been selected and incorporated into breeding programs. Seeds from P. strobus with putative resistance were collected from Oconto River Seed Orchard, Nicolet National Forest, WI. Seedlings were grown for 5 months and artificially inoculated with basidiospores of C. ribicola in two replicated greenhouse experiments. Needles from infected seedlings were fixed, sectioned, and stained with a variety of histological reagents, and rate of mortality for the remaining seedlings was monitored. The most susceptible families suffered 50% mortality in approximately half the time of the more resistant families. Extensive inter- and intracellular hyphae were observed in needles from seedlings of susceptible families, whereas hyphal proliferation was restricted in needles of resistant seedlings. Needles from resistant families had pronounced responses to infection. Phenolics, observed with phloroglucinol-HCl staining, were deposited around infection sites where dense mycelial masses were present. Abnormal host cell growth and rapid cell death in the immediate area of infection were also observed in some eastern white pine families.

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