First Report of the NA2 Lineage of Phytophthora ramorum from an Ornamental Rhododendron in the Interior of California.

In July 2012, we collected a rhododendron var. Trilby with twig dieback symptoms in the lower canopy, consistent with the disease "ramorum blight" caused by Phytophthora ramorum. The symptomatic plant had been planted a year earlier to replace a dead rhododendron in a landscape setting in Placer County, California (Lat: 39.036216°; Long: -120.999274°), Sierra Nevada foothills at ~600 m elevation. Isolations yielded a culture with a fast growth rate and overall morphology resembling the P. ramorum NA2 lineage described by Ivors et al. (4). DNA was extracted from the culture as described previously (4) and six SSR loci: MS18, MS39, MS43, MS45, MS64, MS145, were amplified (2,4). Allelic patterns were compared with those of three testers from each of the three lineages NA1, NA2, and EU1 known to be present in ornamental plants in North America, and they unambiguously confirmed the isolate belongs to the NA2 lineage of the pathogen. Although the symptomatic plant was confined to a landscape setting, it had been planted in that location for a year, providing a possible source of inoculum for the surrounding area. This is the first report of P. ramorum from the Sierra Nevada eco-region in the interior of California. It is also the first report of a NA2 isolate from a plant outside of commercial nurseries in California. The mating type of the isolate was not determined, but NA2 isolates are normally A2, the same mating type of NA1 isolates. The only other report of a NA2 isolate found outside of a nursery is from Washington State (1). Although there is no evidence the pathogen may have infected other plants, the infected rhododendron was found at a location situated over 100 km east of the closest known infestation (www.sodmap.org). Additionally, this is the first report of the pathogen outside the coast mountain range of California. Because the three lineages are genetically and phenotypically distinct (3), the escape of NA2 or EU1 isolates, both still absent from plants in natural settings, could have significant implications for California ecosystems. This finding highlights that introductions of P. ramorum via ornamental plants are still possible, in spite of current regulations. References: (1) G. Chastagner et al. Phytopathology 101:S32, 2011. (2) P. P. Croucher et al. Biol. Invasions 15:2281, 2013. (3) N. J. Grünwald et al. Trends Microbiol. 20:131, 2012. (4) K. Ivors et al. Mol. Ecol. 15:1493, 2006.

Household model of Chagas disease vectors (Hemiptera: Reduviidae) considering domestic, peridomestic, and sylvatic vector populations.

ABSTRACT Disease transmission is difficult to model because most vectors and hosts have different generation times. Chagas disease is such a situation, where insect vectors have 1-2 generations annually and mammalian hosts, including humans, can live for decades. The hemataphagous triatominae vectors (Hemiptera: Reduviidae) of the causative parasite Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) usually feed on sleeping hosts, making vector infestation of houses, peridomestic areas, and wild animal burrows a central factor in transmission. Because of difficulties with different generation times, we developed a model considering the dwelling as the unit of infection, changing the dynamics from an indirect to a direct transmission model. In some regions, vectors only infest houses; in others, they infest corrals; and in some regions, they also infest wild animal burrows. We examined the effect of sylvatic and peridomestic vector populations on household infestation rates. Both sylvatic and peridomestic vectors increase house infestation rates, sylvatic much more than peridomestic, as measured by the reproductive number R0. The efficacy of manipulating parameters in the model to control vector populations was examined. When R0 > 1, the number of infested houses increases. The presence of sylvatic vectors increases R0 by at least an order of magnitude. When there are no sylvatic vectors, spraying rate is the most influential parameter. Spraying rate is relatively unimportant when there are sylvatic vectors; in this case, community size, especially the ratio of houses to sylvatic burrows, is most important. The application of this modeling approach to other parasites and enhancements of the model are discussed.

Root Infections May Challenge Management of Invasive Phytophthora spp. in U.K. Woodlands.

Because sporulation of Phytophthora ramorum and P. kernoviae on Rhododendron ponticum, an invasive plant, serves as primary inoculum for trunk infections on trees, R. ponticum clearance from pathogen-infested woodlands is pivotal to inoculum management. The efficacy of clearance for long-term disease management is unknown, in part due to lack of knowledge of pathogen persistence in roots and emerging seedlings. The main objectives of this work were to (i) investigate whether both pathogens infect R. ponticum roots, (ii) determine the potential for residual inoculum of P. kernoviae to infect R. ponticum seedlings in cleared woodlands, and (iii) assess potential for R. ponticum roots to support survival and transmission of P. kernoviae. Roots of R. ponticum were collected from both unmanaged and cleared woodlands and assessed for pathogen recovery. Both P. ramorum and P. kernoviae were recovered from asymptomatic roots of R. ponticum in unmanaged woodlands, and P. kernoviae was recovered from asymptomatic roots from seedlings in cleared woodland. Oospore production of P. kernoviae was observed in naturally infected R. ponticum foliage and in inoculated roots. Roots also supported P. kernoviae sporangia production. The results of this study suggest that post-clearance management of R. ponticum regrowth is necessary for long-term inoculum management in invaded woodlands.

Survival, dispersal, and potential soil-mediated suppression of Phytophthora ramorum in a California redwood-tanoak forest.

Because the role of soil inoculum of Phytophthora ramorum in the sudden oak death disease cycle is not well understood, this work addresses survival, chlamydospore production, pathogen suppression, and splash dispersal of the pathogen in infested forest soils. Colonized rhododendron and bay laurel leaf disks were placed in mesh sachets before transfer to the field in January 2005 and 2006. Sachets were placed under tanoak, bay laurel, and redwood at three vertical locations: leaf litter surface, litter-soil interface, and below the soil surface. Sachets were retrieved after 4, 8, 20, and 49 weeks. Pathogen survival was higher in rhododendron leaf tissue than in bay tissue, with >80% survival observed in rhododendron tissue after 49 weeks in the field. Chlamydospore production was determined by clearing infected tissue in KOH. Moist redwood-associated soils suppressed chlamydospore production. Rain events splashed inoculum as high as 30 cm from the soil surface, inciting aerial infection of bay laurel and tanoak. Leaf litter may provide an incomplete barrier to splash dispersal. This 2-year study illustrates annual P. ramorum survival in soil and the suppressive nature of redwood-associated soils to chlamydospore production. Infested soil may serve as primary inoculum for foliar infections by splash dispersal during rain events.

Phytophthora ramorum does not cause physiologically significant systemic injury to California bay laurel, its primary reservoir host.

California bay laurel trees (Umbellularia californica) play a crucial role in the reproduction and survival of Phytophthora ramorum in coastal California forests by supporting sporulation during the rainy season and by providing a means for the pathogen to survive the dry, Mediterranean summer. While bay laurel is thus critical to the epidemiology of sudden oak death and other P. ramorum diseases in California, the relatively minor symptoms observed on this reservoir host suggest that it may not sustain ecologically significant injury itself. The long-term role that P. ramorum will play in California forests will depend in part on the extent to which this pathogen decreases the ecological fitness of bay laurel. Despite the importance of this question, no study has yet investigated in detail the physiological impact that ramorum blight imposes on bay laurel. This experimental study quantifies the impact that P. ramorum has on artificially inoculated bay laurel seedlings with measurements that integrate the full injury that infection with an oomycete may cause: photosynthetic efficiency, total photosynthetic area, and growth. Leaf area and leaf mass were not impacted significantly by infection of P. ramorum. Photosynthetic efficiency was mildly depressed in symptomatic, but not asymptomatic leaves, despite unnaturally high levels of necrosis that were imposed on the seedlings. These results demonstrate that bay laurel trees suffer only minor injury from ramorum blight beyond visible necrotic symptoms. Consequently, it is highly likely that bay laurel will continue to be widely available as a host for P. ramorum in California forests, which has long-term implications for the composition of these forests.

Sources of inoculum for Phytophthora ramorum in a redwood forest.

ABSTRACT Sources of inoculum were investigated for dominant hosts of Phytophthora ramorum in a redwood forest. Infected trunks, twigs, and/or leaves of bay laurel (Umbellularia californica), tanoak (Lithocarpus densiflorus), and redwood (Sequoia sempervirens) were tested in the laboratory for sporangia production. Sporangia occurred on all plant tissues with the highest percentage on bay laurel leaves and tanoak twigs. To further compare these two species, field measurements of inoculum production and infection were conducted during the rainy seasons of 2003-04 and 2004-05. Inoculum levels in throughfall rainwater and from individual infections were significantly higher for bay laurel as opposed to tanoak for both seasons. Both measurements of inoculum production from bay laurel were significantly greater during 2004-05 when rainfall extended longer into the spring, while inoculum quantities for tanoak were not significantly different between the 2 years. Tanoak twigs were more likely to be infected than bay laurel leaves in 2003-04, and equally likely to be infected in 2004-05. These results indicate that the majority of P. ramorum inoculum in redwood forest is produced from infections on bay laurel leaves. Years with extended rains pose an elevated risk for tanoak because inoculum levels are higher and infectious periods continue into late spring.

Detection, Distribution, Sporulation, and Survival of Phytophthora ramorum in a California Redwood-Tanoak Forest Soil.

ABSTRACT Recovery of Phytophthora ramorum from soils throughout sudden oak death-affected regions of California illustrates that soil may serve as an inoculum reservoir, but the role of soil inoculum in the disease cycle is unknown. This study addresses the efficacy of soil baiting, seasonal pathogen distribution under several epidemiologically important host species, summer survival and chlamydospore production in soil, and the impact of soil drying on pathogen survival. The efficacy of rhododendron leaves and pears as baits for detection of soilborne propagules were compared. Natural inoculum associated with bay laurel (Umbellularia californica), tanoak (Lithocarpus densiflorus), and redwood (Sequoia sempervirens) were determined by monthly baiting. Summer survival and chlamydospore production were assessed in infected rhododendron leaf disks incubated under bay laurel, tanoak, and redwood at either the surface, the litter/soil interface, or in soil. Rhododendron leaf baits were superior to pear baits for sporangia detection, but neither bait detected chlamydospores. Most inoculum was associated with bay laurel and recovery was higher in soil than litter. Soil-incubated inoculum exhibited over 60% survival at the end of summer and also supported elevated chlamydospore production. P. ramorum survives and produces chlamydospores in forest soils over summer, providing a possible inoculum reservoir at the onset of the fall disease cycle.

Phellinus coronadensis: a new species from southern Arizona, USA.

Phellinus coronadensis is characterized and described morphologically as a new species from southern Arizona, USA. This fungus was previously reported as P. torulosus based on morphological similarities of the basidiomes and type of wood decay. However, P. coronadensis is restricted to two mountain ranges in southern Arizona and found almost exclusively on living southwestern white pine (Pinus strobiformis). Phellinus torulosus is found primarily in Europe and parts of Asia and is primarily associated with hardwood hosts. Based on sequence analysis of small subunit mitochondrial ribosomal DNA (mt-SSU), we determined that P. coronadensis is in a different lineage from P. torulosus and apparently more closely related to the P. pini complex. The taxon associated with southwestern white pine, being distinct and not yet having been validly named, is proposed as a new species here.

First Report of Phytophthora ramorum on Canyon Live Oak in California.

During August 2002, Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from branches <2.0 cm in diameter on a canyon live oak (Quercus chrysolepis) in Mt. Tamalpais State Park, Marin County, CA. The shrub was a cluster of stems <1 m in diameter and 1 m high. Similar cankers were observed on small branches of adjacent canyon live oaks and there was dieback of the branches distal to the lesions. Many tanoak (Lithocarpus densiflorus), California bay laurel (Umbellularia californica), and evergreen huckleberry (Vaccinium ovatum) were also infected by P. ramorum at this site. The isolate was identified as P. ramorum by its abundant chlamydospores and caducous, semi-papillate sporangia and internal transcribed spacer (ITS) rDNA sequences identical to those of isolates of P. ramorum from Quercus spp., tanoak, and Rhododendron (1,3). To test for pathogenicity, two greenhouse trials (5 seedlings per trial plus controls) were conducted on 20- to 24-month-old canyon live oak seedlings. Coast live oak (Q. agrifolia, section Lobatae) seedlings were included in the trials as a comparison because the species is known to be susceptible (1). Stems (approximately 1 cm in diameter) were wound inoculated (1). After 6 weeks, lesion lengths in the cambium of canyon live oak averaged 17.2 mm (range 16 to 30 mm), which was significantly greater (analysis of variance [ANOVA], P < 0.05) in both trials than those of control inoculations (mean = 6 mm). Coast live oak seedlings inoculated at the same time had mean lesion lengths of 22.6 mm (range 15 to 30 mm). P. ramorum was recovered from 100% of inoculated stems. Canyon live oak has a wide geographic range within California, but is not common in the areas currently affected by P. ramorum. We have not observed disease symptoms or unusual mortality on overstory canyon live oaks. Although a number of understory canyon live oaks at the site on Mt. Tamalpais were apparently infected, the long-term effect of P. ramorum infection on understory trees remains unclear. To our knowledge, this is the first report of infection by P. ramorum of an oak species outside of the section Lobatae (red oaks); canyon live oak is classified in the section Protobalanus (intermediate or golden cup oaks) (2). Oaks in the section Quercus (white oaks) have not been observed to be infected by P. ramorum in the field. References: (1) D. M. Rizzo et al. Plant Dis. 86:205, 2002. (2) P. Manos et al. Mol. Phylogenet. Evol. 12:333, 1999. (3) S. Werres et al. Mycol. Res. 105:1155, 2001.

Development of Fungicide Cross Resistance in Helminthosporium solani Populations from California.

Helminthosporium solani populations on potato from the Tulelake area in California frequently have been exposed to thiophanate-methyl but not benomyl. Assessment of three H. solani populations found that 182 of 238 isolates were resistant to both thiophanate-methyl and benomyl and 56 isolates were sensitive to both fungicides. None of the isolates exhibited a differential reaction to the two fungicides. The effective concentrations that reduced growth by 50% for resistant isolates of H. solani were approximately 400 mg/liter for thiophanate- methyl and 35 mg/liter for benomyl. Two point mutations were detected in the ß-tubulin gene from H. solani isolates from California; however, only the mutation at the 455-nucleotide position (codon 198) was strongly associated with thiophanate-methyl resistance. This mutation led to a change of glutamic acid to alanine at codon 198. Independent of fungicide resistance, a mutation at the 836-site was detected in all California isolates. A polymerase chain reaction (PCR)-based restriction fragment length polymorphism (RFLP) assay was used to identify thiophanate-methyl resistance in H. solani; resistant isolates exhibited two DNA fragments of 390 and 482 bp, whereas sensitive isolates had three fragments of 62, 390, and 420 bp. Every isolate assigned either as resistant or sensitive by the PCR-based RFLP assay correlated 100% with the results of the assay on fungicide-amended medium.

Spatial Distribution of Armillaria mellea in Pear Orchards.

Pears have traditionally been considered to be highly resistant to Armillaria root disease (causal agent: Armillaria mellea). In recent years, however, the incidence of Armillaria root disease in pears has increased in California. To determine the spatial distribution of Armillaria root disease in the field, a total of 156 isolates of Armillaria were collected from dead and dying pear trees located within two orchards in Lake County. All isolates from these two orchards, as well as from an additional 10 pear orchards, were identified as Armillaria mellea sensu stricto. Based on pairings among 102 Armillaria isolates, four somatic incompatibility groups (SIGs) were identified at orchard 1. Three of the four SIGs at this site were over 100 m in length; the largest SIG was at least 200 m in length. Pairings among 54 isolates identified five SIGs at orchard 2. The SIGs at orchard 2 were generally smaller than those detected at orchard 1 and ranged from 20 to 60 m in length. The size of the SIGs points toward long-term establishment of the fungus on the two sites, most likely predating the establishment of the pear orchards. Extensive root excavations of 19 trees indicated that the primary means of secondary spread of Armillaria was via rhizomorphs, as opposed to root-to-root contact.

First Report of Phytophthora ramorum on Douglas-Fir in California.

Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from three Douglas-fir (Pseudotsuga menziesii) saplings in a mixedevergreen forest in Sonoma County, California. Symptoms on these saplings included cankers on small branches (0.5 to 1 cm in diameter) resulting in wilting of new shoots, dieback of branches, and loss of leaves as much as 15 cm from the twig tip. Symptoms were observed on most saplings growing in the same area. On several smaller saplings (<1 m tall), P. ramorum infection resulted in the death of the leader and the top several whorls of branches. Isolates were identified as P. ramorum by their abundant chlamydospores and caducous, semi-papillate sporangia (2) and internal transcribed spacer rDNA sequences identical to those of isolates of P. ramorum from Quercus spp., Lithocarpus densiflorus, and Rhododendron (1,2). To test for pathogenicity, foliage inoculations were conducted on seedlings in two trials by misting 30 leaves per trial (five leaves per seedling plus controls) with sterile distilled water and pinning inoculum plugs, taken from the margin of P. ramorum cultures, to the upper surface of leaves. Inoculation resulted in lesions ranging between 1 and 12 mm long, and P. ramorum was recovered from 47% of inoculated leaves. Symptoms were not restricted to inoculated leaves, and in 26 single-leaf inoculations, lesions 17 to 85 mm long developed on branches (five mm in diameter) adjacent to the inoculated leaf. Isolation success from branch lesions was 50%, despite the fact that such lesions were apparently disjunct from the small 1-mm lesions developing on inoculated leaves. Stems of Douglas-fir seedlings (approximately 1 cm in diameter) were wound inoculated (1) in two trials consisting of 10 inoculated seedlings per trial plus 10 controls. After 6 weeks, lesion lengths in the cambium averaged 38 mm (range 12 to 62 mm), and three seedlings were completely girdled. P. ramorum was recovered from 75% of inoculated stems. Mean lesion lengths on seedlings inoculated with P. ramorum were significantly greater (P < 0.05) in both trials than those of control inoculations (mean 9 mm) based on analysis of variance. We have not observed unusual mortality or disease symptoms on overstory Douglas-fir trees in natural forests. The importance of P. ramorum branch tip dieback for growth and reproduction of Douglas-fir is unknown. Douglas-fir is present in many forests in California and Oregon already infested by P. ramorum, yet we have found infection of plants at only one location. At this site, symptomatic Douglas-fir saplings were surrounded by bay laurel (Umbellularia californica) trees with extremely high levels of P. ramorum infection. P. ramorum is known to sporulate prolifically on bay laurel leaves. More studies are necessary to determine if the incidence of P. ramorum in Douglas-fir extends to other locations or if it is limited to this one locale. References: (1) D. M. Rizzo et al. Plant Disease 86:205, 2002. (2) S. Werres et al. Mycol. Res. 105:1155, 2001.

Effects of Temperature and Water Vapor Pressure on Conidial Germination and Lesion Expansion of Sphaerotheca macularis f. sp. fragariae.

Conidial germination in vitro and foliar lesion expansion were studied for Sphaerotheca macularis f. sp. fragariae. Detached strawberry (Fragaria × ananassa) leaves were inoculated, then held in controlled environments of constant temperatures (4 to 36°C) and relative humidity (RH, 32 to 100%) representing the range of these variables observed under California commercial production conditions. Percent germination and lesion expansion rate were determined by destructive subsampling over time. Conidia germinated at all temperatures by 6 h and reached a maximum by 48 h, with the optimum near 20°C. Lesions were marked with the aid of a microscope and measured by computer-assisted image-analysis to determine expansion rate. Maximal rates occurred at 25°C. Several growth models were fit to the expansion rate data with high significance. Predicted optima from these models ranged from 22 to 27°C and/or 17 to 27 mm Hg VPwater@100%RH. Neither RH, partial vapor pressure of water (VPwater), nor vapor pressure deficit (VPD) correlated with lesion expansion rate, adding to studies minimizing the importance of RH and VPD as determinants of asexual phase powdery mildew growth other than specifically at spore germination.

Disease Progression of Phytophthora ramorum and Botryosphaeria dothidea on Pacific Madrone.

Infection by Phytophthora ramorum was associated with stem and leaf lesions of Pacific madrone (Arbutus menziesii) seedlings and saplings. In addition, a common and native pathogen, Botryosphaeria dothidea, caused similar leaf and stem lesions. When exposed to natural levels of inoculum in forests infested with P. ramorum, 50 to 66% of madrone saplings used as bait died. Recovery of P. ramorum from colonized plant tissue on culture media was generally low. From initial infection, P. ramorum was not culturable from leaf tissue after a mean of 3.5 weeks or from stem tissue after a mean of 8 weeks. Generally, B. dothidea was recovered more frequently from necrotic stems and leaves than was P. ramorum. Experimental inoculations of madrone seedlings showed that leaf and stem lesion lengths were, on average, greater on tree seedlings inoculated with P. ramorum than on those inoculated with B. dothidea. P. ramorum and B. dothidea appear to coexist in stem and leaf tissue, forming a novel pathogen complex, affecting growth and reproduction of Pacific madrone.

First Report of Phytophthora ramorum on Coast Redwood in California.

Phytophthora ramorum S. Werres & A.W.A.M. de Cock was isolated from discolored leaves and cankers on small branches (<0.5 cm in diameter) on 27 coast redwood (Sequoia sempervirens) saplings (2 to17 cm in diameter) at two locations in California (Jack London State Park, Sonoma County and Henry Cowell State Park, Santa Cruz County). Symptoms were observed on branches throughout the crowns of affected trees. Isolates were identified as P. ramorum by their abundant chlamydospores and caducous, semi-papillate sporangia (2) and internal transcribed spacer (ITS) rDNA sequences identical to those of P. ramorum from Quercus spp., Lithocarpus densiflorus, and Rhododendron (1,2). P. ramorum was also detected in dying basal sprouts on mature redwood trees from an additional five locations in coastal California by polymerase chain reaction (PCR) amplification of the ITS region using DNA extracted from symptomatic tissue and P. ramorum-specific PCR primers. To test for pathogenicity, foliage inoculations were conducted on redwood seedlings in two trials by misting 30 leaves per trial (five leaves per seedling plus controls) with sterile distilled water and then pinning inoculum plugs to the upper surface of leaves. Inoculation resulted in lesions of 1 to 20 mm on individual leaves, and P. ramorum was recovered from 43% of inoculated leaves. Symptoms were not restricted to inoculated leaves because 15 inoculations of individual leaves led to discoloration of two or more adjacent leaves. On one inoculation, 60 mm of the adjacent stem was killed. Stems of redwood seedling (approximately 1 cm in diameter) were wound inoculated (1) in two trials consisting of 10 inoculated seedlings per trial plus 10 controls. After 6 weeks, lesion lengths in the cambium caused by P. ramorum averaged 13.7 mm (range 4 to 21 mm). P. ramorum was recovered from 100% of inoculated stems. Entire branches near the inoculation point became chlorotic even though no direct connection was evident between the lesion and the branches. No chlorosis was observed among the control inoculations. Mean lesion lengths of inoculated stems were significantly greater in both trials than those of control inoculations (mean 6.2 mm) at P < 0.05 based on analysis of variance (ANOVA). Redwood saplings (2.5 to 4.5 cm in diameter) were also wound inoculated in a separate trial. No phloem or cambial discoloration was observed after 7 weeks, but necrotic lesions in the xylem had a mean length of 39 mm (range 12 to 73 mm). In addition, narrow streaks, 1 to 2 mm in diameter, were also noted in the xylem extending from the necrotic areas upward to 90 cm. P. ramorum was recovered from 70% of inoculated stems in this trial. Mean lesion lengths of P. ramorum were significantly greater in all trials than those of control inoculations (mean 20 mm) at P < 0.05 based on ANOVA. While P. ramorum causes a lethal canker on Quercus spp. and L. densiflorus (1), we have not observed unusual mortality or disease symptoms on overstory redwoods in natural forests. The impact of infection by P. ramorum on understory redwoods is also unclear. However, the pathogen appears to be able to kill sprouts. References: (1) D. M. Rizzo et al. Plant Dis. 86:205, 2002. (2) S. Werres et al. Mycol. Res. 105:1155, 2001.

Phytophthora ramorum as the Cause of Extensive Mortality of Quercus spp. and Lithocarpus densiflorus in California.

A new canker disease, commonly known as sudden oak death, of Lithocarpus densiflorus, Quercus agrifolia, Q. kelloggii, and Q. parvula var. shrevei in California is shown to be caused by Phytophthora ramorum. The pathogen is a recently described species that previously was known only from Germany and the Netherlands on Rhododendron spp. and a Viburnum sp. This disease has reached epidemic proportions in forests along approximately 300 km of the central coast of California. The most consistent and diagnostic symptoms on trees are cankers that develop before foliage symptoms become evident. Cankers have brown or black discolored outer bark and seep dark red sap. Cankers occur on the trunk at the root crown up to 20 m above the ground, but do not enlarge below the soil line into the roots. Individual cankers are delimited by thin black lines in the inner bark and can be over 2 m in length. In L. densiflorus saplings, P. ramorum was isolated from branches as small as 5 mm in diameter. L. densiflorus and Q. agrifolia were inoculated with P. ramorum in the field and greenhouse, and symptoms similar to those of naturally infected trees developed. The pathogen was reisolated from the inoculated plants, which confirmed pathogenicity.

[Spigelian hernia: anatomo-clinical considerations]. / L'ernia di Spigelio. Considerazioni anatomo-cliniche.

Two cases of Spigelian hernia are reported. Starting from the analysis of these cases, some observations about the anatomy, the etiology, clinic, diagnostic methods and the best therapeutic choices now available for this uncommon pathology are presented.

Phylogenetic divergence in a local population of the ectomycorrhizal fungus Cenococcum geophilum.

Cenococcum geophilum is a widely distributed mycorrhizal species associated with diverse gymnosperm and angiosperm hosts. In previous studies, a significant amount of genetic and genotypic diversity has been detected in this species, despite the fact that C. geophilum is not thought to reproduce by meiotic or mitotic spores. We conducted a phylogenetic analysis of 103 C. geophilum isolates from a California oak woodland and seven non-California isolates using a glyceraldehyde 3-phosphate dehydrogenase gene. In addition, a subset of isolates was analyzed using sequences from ITS-rDNA, a Group I intron located in the 3' end of the SSU-rDNA and a portion of the mitochondrial SSU-rDNA. Phylogenetically distinct lineages, or cryptic species, of C. geophilum were detected at the scale of a single soil sample within our field site. As much genetic diversity was found within a soil sample as was found for isolates collected across the USA. Our results help explain the large amount of physiological, phenotypic, and genetic differences reported among isolates of C. geophilum from similar as well as diverse geographic regions. The ecological role that these sympatric cryptic species play remains to be determined.

Household model of Chagas disease vectors (Hemiptera: Reduviidae) considering domestic, peridomestic, and sylvatic vector populations

Disease transmission is difficult to model because most vectors and hosts have different generation times. Chagas disease is such a situation, where insect vectors have 1-2 generations annually and mammalian hosts, including humans, can live for decades. The hemataphagous triatominae vectors (Hemiptera: Reduviidae) of the causative parasite Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) usually feed on sleeping hosts, making vector infestation of houses, peridomestic areas, and wild animal burrows a central factor in transmission. Because of difficulties with different generation times, we developed a model considering the dwelling as the unit of infection, changing the dynamics from an indirect to a direct transmission model. In some regions, vectors only infest houses; in others, they infest corrals; and in some regions, they also infest wild animal burrows. We examined the effect of sylvatic and peridomestic vector populations on household infestation rates. Both sylvatic and peridomestic vectors increase house infestation rates, sylvatic much more than peridomestic, as measured by the reproductive number R0. The efficacy of manipulating parameters in the model to control vector populations was examined. When R0 > 1, the number of infested houses increases. The presence of sylvatic vectors increases R0 by at least an order of magnitude. When there are no sylvatic vectors, spraying rate is the most influential parameter. Spraying rate is relatively unimportant when there are sylvatic vectors; in this case, community size, especially the ratio of houses to sylvatic burrows, is most important. The application of this modeling approach to other parasites and enhancements of the model are discussed