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The objectives of this study were i) to give a taxonomic description of a fungus phylogenetically related to Neofabraea and assign the name Cryptosporiopsis kienholzii to this fungus, ii) to expand previous Neofabraea species profiles from infected apple and pear fruit collected from major pome fruit production districts in Oregon and Washington, and iii) to determine the sensitivity of Neofabraea alba, Neofabraea malicorticis, Neofabraea perennans, and C. kienholzii to a range of fungicides. A name is given herein to the anamorph of the fungus previously called 'Neofabraea sp. nov.' in the literature, and the fungus is designated as C. kienholzii. The teleomorph of this fungus has never been observed in vivo or in vitro. N. alba, N. perennans, and C. kienholzii accounted for 61.3, 35.6, and 3.1 %, respectively, of 608 isolates obtained from pear fruit and 6.0, 81.3, and 12.7 % of 150 isolates from apple fruit. N. alba was the most common species in Oregon and N. perennans was most common in Washington. N. malicorticis was not found in any of the districts and may be limited to the wet climates west of the Cascade mountain range. C. kienholzii occurs in pome fruit orchards from southern Oregon to North Central Washington, and this is the first report of C. kienholzii in the state of Washington. The four most effective fungicides for control of bull's-eye rot caused by all species were thiabendazole, thiophanate-methyl, pyrimethanil, and pyraclostrobin+boscalid. Other fungicides gave acceptable control of some species of Neofabraea but not others. There was good agreement of the microbioassay with fungicide evaluations using wound-inoculated pear fruit for five of seven fungicides, but the microbioassay was not consistent enough for determination of the sensitivity of Neofabraea species to new fungicides.

Potebniamyces pyri is the cause of Phacidiopycnis rot of d'Anjou pear, which is grown primarily in Washington and Oregon. To estimate the population structure of P. pyri, 146 single-spore isolates were sampled from five major pear-production areas and scored for variation at eight sequence-characterized amplified region (SCAR) loci. Significant genetic differentiation was detected among five subpopulations and a total of 54 multilocus genotypes were identified, with significant genotypic diversity in each subpopulation. No genotype was shared among more than three subpopulations. To estimate the relationship between phenotype and multilocus SCAR genotype, four to five representative isolates of each dominant SCAR genotype in each subpopulation were assayed for growth rate on oatmeal agar and virulence on d'Anjou pear fruit. Significant differences in daily growth rates and virulence were detected among genotypes; however, genotype was not predictive of virulence. To assess the mating system of the pathogen, 10 ascospores were sampled from each of 20 apothecia from a commercial orchard and scored for five SCAR markers. Segregation of alleles at one or more SCAR loci was detected among 18 of 20 ascospore progeny sets, indicating that P. pyri is likely a heterothallic fungus with a predominantly outcrossing mating system.