Identification and Pathogenicity of Fungal Species Associated with Branch Canker and Shoot Blight on Persimmons (Diospyros kaki) in California

Persimmon is a relatively new crop to California agriculture. Asian persimmons (Diospyros kaki) are the dominant species commercially cultivated in the United States, primarily grown in California, covering approximately 1,153 ha of bearing trees. In the growing seasons of 2020 and 2021, unusual shoot blight and branch cankers were observed in several persimmon orchards in San Joaquin and Solano counties in California. The most prevalent symptoms were well-defined black discoloration in the cambium and streaking in the vascular tissues of green shoots. On woody branches and old pruning wounds, symptoms manifested as black wedge-shaped cankers. Isolations from affected tissues revealed the occurrence of Diaporthe species, including D. chamaeropis, D. foeniculina, and an undescribed Diaporthe sp. as the most frequent isolated pathogens, followed by Eutypella citricola and Phaeoacremonium iranianum. The isolates were identified through multilocus phylogenetic analyses using nucleotide sequences of the rDNA internal transcribed spacer, β-tubulin, and translation elongation factor 1-alpha genes. To fulfill Koch's postulates, mycelium plugs of the various fungal species identified were inserted in 2-year-old branches of mature persimmon trees after making wounds using a corkborer in field conditions. Results showed that Diaporthe spp., E. citricola, and P. iranianum are the main causal agents of branch canker and shoot dieback of persimmon trees in California, with Diaporthe spp. being the most frequently isolated pathogen.

Reassessing the Etiology of Aspergillus Vine Canker and Summer Bunch Rot of Table Grapes in California

Fungal taxonomy is in constant flux, and the advent of reliable DNA barcodes has enabled the enhancement of plant pathogen identification accuracy. In California, Aspergillus vine canker (AVC) and summer bunch rot (SBR) are economically important diseases that affect the wood and fruit of grapevines, respectively, and their causal agents are primarily species of black aspergilli (Aspergillus section Nigri). During the last decade, the taxonomy of this fungal group has been rearranged several times using morphological, physiological, and genetic analyses, which resulted in the incorporation of multiple cryptic species that are difficult to distinguish. Therefore, in this study, we aimed to reassess the etiology of AVC and SBR using a combination of morphological observations with phylogenetic reconstructions based on nucleotide sequences of the calmodulin (CaM) gene. Results revealed that the isolates causing AVC from recent isolations corresponded to A. tubingensis, whereas the isolates obtained from initial surveys when the disease was discovered were confirmed as A. niger and A. carbonarius. Similarly, the isolates obtained from table grapes with SBR symptoms and from spore traps placed in those vineyards were identified primarily as A. tubingensis, followed by A. niger and A. carbonarius. Notably, the A. niger isolates formed a subclade with strains previously known as A. welwitschiae, which is a species that was recently synonymized with A. niger. Overall, the most prevalent species was A. tubingensis, which was associated with both AVC and SBR, and representative isolates recovered from AVC-symptomatic wood, berries SBR symptoms, and spore traps were equally pathogenic in healthy wood and berries of 'Red Globe' grapevines. This study also constitutes the first report of A. tubingensis causing AVC and SBR of grapes in California and in the United States.

Identification and Pathogenicity of Fusarium Species Associated with Young Vine Decline in California

Grapevine trunk diseases are caused by a broad diversity of fungal taxa that have serious impacts on the worldwide viticulture industry due to significant reductions in vineyards yield and lifespan. Field surveys carried out from 2018 to 2022 in California nurseries and young vineyards revealed a high incidence of Fusarium. Since Fusarium species are important pathogens of other perennial crops, the present study aimed to identify and determine the pathogenicity of the Fusarium species on grapevines. Morphology of the fungal colonies coupled with multilocus phylogenetic analyses using nucleotide sequences of the translation elongation factor 1-alpha (tef1) and the RNA polymerase II second largest subunit (rpb2) genes revealed the occurrence of 10 species clustering in six species complexes, namely F. fujikuroi (FFSC), F. oxysporum (FOSC), F. solani (FSSC), F. sambucinum (FSAMSC), F. incarnatum-equiseti (FIESC), and F. tricinctum (FTSC) species complexes. The species F. annulatum (FFSC) was the most prevalent in samples from both symptomatic young vineyards (73.5% incidence) and nursery propagation material (62.5% incidence). Pathogenicity of the 10 most frequent species was confirmed by fulfilling Koch's postulates on living woody tissue of 1103 Paulsen rootstocks. Our results suggest that Fusarium spp. are involved in the development of young vine decline, probably as opportunistic pathogens when grapevines are under stress conditions.

First report of Diplodia bulgarica causing black canker on apple in California

California is the sixth largest apple-producing state in the United States with a production that reached 4,654 ha in 2021. During the late winter of 2023, black canker symptoms were observed on branches of 'Gravenstein' apple (Malus domestica) in two commercial orchards in Sonoma County, California. The prevalence of symptomatic trees ranged from 10 to 30%. External symptoms included charcoal looking-cankers with the bark peeling off from the primary and secondary branches. Internally, cankers were dark brown in color with a hard consistency. Pycnidia were observed on the surface of older cankers. Fungal isolations were performed from disinfected (70% ethanol, 30 s) symptomatic branch samples (n = 15). Small wood pieces (5 mm length) were taken from the margin of diseased and healthy tissues, and placed on potato dextrose agar acidified with 92% lactic acid at 0.5 mL per liter (APDA). Plates were incubated at room temperature (20-22 °C) for 7 days. Colonies of Botryosphaeriaceae species (Phillips et al. 2013) (n = 12) were consistently recovered and pure cultures were obtained by transferring a single hyphal tip onto fresh APDA. Colonies were light gray with irregular margins. To induce pycnidia formation, two isolates (UCD11350 and UCD11351) were grown on pistachio leaf agar for 21 days. Conidia (n = 50) were thick-walled and ovoid in shape, initially hyaline, then turned pale brown and dark brown at maturity, and some of them became 1-septate, ranging from 18.9 to 24.0 (21.9) × 11.5 to 14.7 (13.4) µm. Isolates were identified by sequencing a partial region of the beta-tubulin (tub2) gene using the primers Bt2a/Bt2b (Glass and Donaldson 1995). BLAST searches on NCBI GenBank revealed 99.5 % identity with the Diplodia bulgarica ex-type (CBS 1245254). To confirm the identity, the rRNA internal transcribed spacer (ITS) and the translation elongation factor 1-alpha (tef1) were also sequenced using ITS5/ITS4 (White et al. 1990), and EF1-688F/EF1-1251R (Alves et al. 2008), respectively. A maximum parsimony multi-locus phylogenetic analysis clustered Californian isolates with reference strains of D. bulgarica. Sequences were deposited in GenBank (nos. OR631209 to OR631210, OR637361 to OR637362, OR637363 to OR637364 for ITS, tub2, and tef1, respectively). Pathogenicity tests were conducted on 2 to 3-year-old branches (n = 5) of over 20-year-old trees by inserting a 5-mm segment of a toothpick, completely colonized with each of the two isolates mentioned above, into a 1-mm-diameter hole made with a sterile drill bit. The same number of branches where mock inoculated with a non-colonized toothpick as negative control. The experiment was performed twice. After ten weeks, inoculations resulted in dark brown necrotic lesions that ranged from 54.0 to 59.8 mm in length. Negative controls remained asymptomatic. Koch's postulates were fulfilled by successfully recovering the isolates from the lesion margins, which were confirmed by morphology. Diplodia bulgarica was first described affecting M. sylvestris in Bulgaria (Phillips et al. 2012), and then detected on M. domestica causing cankers in Iran (Abdollahzadeh 2015), India (Nabi et al. 2020), Germany (Hinrichs-Berger al. 2021) and Türkiye (Eken 2021). The pathogen was also identified causing postharvest fruit rot (Eken 2022). To our knowledge, this is the first report of D. bulgarica causing branch canker on apple in California, which provides important information for developing detection and control strategies.

First report of Phyllactinia chubutiana causing powdery mildew on Goji berry plants (Lycium barbarum and L. chinense) in the United States

Goji berries, both Lycium barbarum, and L. chinense, are native to Asia and have been highly valued for food and medicinal purposes for more than 2,000 years (Wetters et al. 2018). These species are difficult to distinguish due to the extensive cultivar development of the former and the plasticity of the latter's phenotypes. During the summers (from July to September) of 2021 and 2022, powdery mildew was observed in Goji berry plants (L. barbarum and L. chinense) in both community and residential gardens, in Yolo Co., California. Disease severity varied between 30 and 100% of infected leaves per plant. Host identity was confirmed by phylogenetic analysis using sequences of the psbA-trnH intergenic region (Wetters et al. 2018). Powdery mildew was characterized by the presence of white fungal colonies on both sides of the leaves and the fruit sepals. Colorless adhesive tape mounts of the fungal structures were examined in drops of 3% KOH. Epidermal strips of infected leaves were peeled off for analysis of the mycelia. Hyphae were both external and internal, hyaline, septate, branched, smooth, and 2.5 to 5.8 (4.3) µm wide (n = 50). Appressoria were nipple-shaped to irregularly branched and solitary or opposite in pairs. Conidiophores were hyaline, erect, and simple. Foot cells were cylindrical, straight, 13.1 to 48.9 (29.8) × 5.0 to 8.2 (6.8) µm (n = 20), followed by 0 to 2 cells. Conidia lacked fibrosin bodies, were borne singly, unicellular, hyaline, and ellipsoid when young. Mature conidia were either cylindrical or slightly centrally constricted to dumb-bell-like, and 36.2 to 51.8 (44.9) × 15.1 to 22.0 (18.9) µm (n = 50), with conspicuous subterminal protuberances. Germ tubes were subterminal, either short with multilobate apex or moderately long with a simple end. Chasmothecia were not observed. Morphologically the fungus matched the description of Phyllactinia chubutiana Havryl., S. Takam. & U. Braun (Braun and Cook, 2012). The pathogen identity was further confirmed by amplifying and sequencing the rDNA internal transcribed spacer (ITS) and the 28S rDNA gene using the primer pairs ITS1/ITS4 (White et al. 1990) and PM3/TW14 (Takamatsu and Kano 2001, Mori et al. 2000). The resulting sequences (GenBank OP434568 to OP434569; and OP410969 to OP410970) were compared with the NCBI database using BLAST, showing 99% similarity to the ex-type isolate of P. chubutiana (BCRU 4634, GenBank AB243690). Maximum parsimony phylogenetic analysis clustered our isolates with reference sequences of P. chubutiana from various hosts deposited in GenBank. Pathogenicity was confirmed by inoculating two two-year-old L. barbarum potted plants. Four leaves per plant were surface disinfected (75% ethanol, 30 s) before gently rubbing powdery mildew infected leaves onto healthy leaves. Healthy leaves were used for mock inoculations. All plants were maintained in a growth chamber at 22°C and 80% relative humidity (RH) for five days and then 60% RH thereafter. Inoculated leaves developed powdery mildew symptoms after 28 days, and P. chubutiana colonies were confirmed by morphology, hence fulfilling Koch's postulates. Control leaves remained symptomless. Phyllactinia chubutiana (= Oidium insolitum, Ovulariopsis insolita) was first described on L. chilense in Argentina (Braun et al. 2000, Havrylenko et al. 2006), and later reported on L. chinense in China (Wang Yan et al. 2016). To our knowledge, this is the first report of P. chubutiana causing powdery mildew on L. barbarum and L. chinense in the United States, which provides crucial information for developing effective strategies to monitor and control this newly described disease.

First Report of Neofusicoccum mediterraneum and Neofusicoccum parvum Causing Pine Ghost Canker on Pinus spp. in Southern California

Pinus eldarica, P. halepensis and P. radiata are important conifer species native to Mediterranean regions that are cultivated in the southwestern United States for landscaping (Phillips and Gladfelter, 1991; Chambel et al., 2013). Among them, Monterey pine (P. radiata) is native to restricted areas of California and Mexico, but it is extensively grown for timber production in other countries, especially in the Southern Hemisphere (Rogers, 2004). From 2018 to 2022, severe dieback and cankers have been detected on more than 30 mature pines of the three species within a 40-ha urban forest in Orange County, Southern California. Symptoms initiate on the lower portion of the canopy and advance into the crown, leading to quick dieback and, in some cases, to tree death. Cross sections of affected branches revealed wedged cankers with irregular, indistinct margins, and cryptic discoloration (i.e., "ghost cankers"). Pycnidia were observed on the surface of each bark scale of branches with advanced infections. Two morphotypes of Botryosphaeriaceae colonies (n = 34 isolates) were recovered consistently from more than 90% of the symptomatic pines. Two isolates per morphotype were grown on pistachio leaf agar (Chen et al., 2014) for 14 days to induce pycnidia formation. Conidia (n = 50) were hyaline, thin-walled and fusoid to ellipsoidal in shape, ranging from 16.1 to 27.9 (22.6) × 5.4 to 8.2 (6.8) µm for the first morphotype and 11.5 to 20.4 (16.3) × 4.8 to 8.6 (6.3) µm for the second morphotype. The rDNA internal transcribed spacer (ITS), beta-tubulin (tub2), and translation elongation factor 1-alpha (tef1-α) partial gene regions were amplified and sequenced using the primers ITS5/ITS4 (White et al., 1990), Bt2a/Bt2b (Glass and Donaldson, 1995), and EF1-728F/EF1-986R (Carbone and Kohn, 1999), respectively. A multi-locus phylogenetic analysis revealed that isolates UCD9433 and UCD10439 clustered with the ex-type strain of Neofusicoccum mediterraneum (CBS:113083), and isolates UCD9161 and UCD9434 grouped with N. parvum (CMW:9081). Sequences were submitted to GenBank (nos. OP535391 to OP535394 for ITS, OP561946 to OP561949 for tef1-α, and OP561950 to OP561953 for tub2). Pathogenicity tests were performed with above-mentioned isolates on 20-mm-diameter healthy branches of mature Monterey pines (n = 10, 14 years old) located in a research field at UC Davis. Isolates were grown for 7 days on potato dextrose agar and inoculated in the internode area by removing a 5-mm-diameter disk of the bark with a sterile cork borer and placing a 5-mm-diameter mycelial plug. Controls were mock-inoculated with sterile agar plugs, and the experiment was performed twice. After three months, inoculations resulted in vascular lesions that ranged from 20.6 to 49.7 (32.7) mm with N. mediterraneum and from 13.5 to 71.0 (33.6) mm with N. parvum, and the same pathogens were reisolated (70 to 100% recovery). Controls remained symptomless and no botryosphaeriaceous colonies were recovered. Both N. mediterraneum and N. parvum are polyphagous pathogens associated with multiple woody plant hosts (Phillips et al., 2013). Previously, only N. parvum has been associated with pine cankers in Iran, however, the pine species was not indicated (Abdollahzadeh et al., 2013). The detection of these pathogens in urban forests raises concerns of potential spillover events to other forest and agricultural hosts in Southern California. To our knowledge, this is the first report of N. mediterraneum and N. parvum causing Pine Ghost Canker on P. eldarica, P. halepensis and P. radiata.

Evaluation of the Antifungal Activity of Endophytic and Rhizospheric Bacteria against Grapevine Trunk Pathogens

Grapevine trunk diseases (GTDs) are caused by multiple unrelated fungal pathogens, and their management remains difficult worldwide. Biocontrol is an attractive and sustainable strategy given the current need for a cleaner viticulture. In this study, twenty commercial vineyards were sampled across California to isolate endophytic and rhizospheric bacteria from different grapevine cultivars with the presence and absence of GTD symptoms. A collection of 1344 bacterial isolates were challenged in vitro against Neofusicoccum parvum and Diplodia seriata, from which a subset of 172 isolates exerted inhibition levels of mycelial growth over 40%. Bacterial isolates were identified as Bacillus velezensis (n = 154), Pseudomonas spp. (n = 12), Serratia plymuthica (n = 2) and others that were later excluded (n = 4). Representative isolates of B. velezensis, P. chlororaphis, and S. plymuthica were challenged against six other fungal pathogens responsible for GTDs. Mycelial inhibition levels were consistent across bacterial species, being slightly higher against slow-growing fungi than against Botryosphaeriaceae. Moreover, agar-diffusible metabolites of B. velezensis strongly inhibited the growth of N. parvum and Eutypa lata, at 1, 15, and 30% v/v. The agar-diffusible metabolites of P. chlororaphis and S. plymuthica, however, caused lower inhibition levels against both pathogens, but their volatile organic compounds showed antifungal activity against both pathogens. These results suggest that B. velezensis, P. chlororaphis and S. plymuthica constitute potential biocontrol agents (BCAs) against GTDs and their application in field conditions should be further evaluated.

Dothiorella sarmentorum Causing Branch Dieback of English Walnut in Maule Region, Chile

English walnut (Juglans regia), cv. Chandler is the most cultivated tree nut in Chile, with 43,734 ha. In Maule Region, central Chile, English walnut plantings have expanded over an additional 7,000 ha in the last five years. During a routine orchard survey in 2019, branch and twig dieback symptoms were observed in two commercial orchards located in San Rafael (10 years old) and Longaví (12 years old) in the Maule Region, with an incidence of 45% to 65% of affected trees, respectively. Symptomatic branch samples (n = 15) were collected from the two commercial orchards and transported to the laboratory in a cooler and then surface sterilized in 96% ethanol for 3 s and briefly flamed. Cross-section of symptomatic branches revealed brown to dark-brown wedge-shaped wood cankers. Small (5 mm) pieces of wood from the edge of cankered tissues were placed on Potato Dextrose Agar (PDA, 2%) amended with 0.005% tetracycline, 0.01% streptomycin, and 0.1% Igepal CO-630 (PDAm) (Díaz and Latorre 2014) and incubated at 25°C for five days in the dark. Pure cultures were obtained by transferring a hyphal tip from growing colonies to fresh PDA media. Each fungal isolate was recovered from a single diseased branch (47%). Seven isolates (Dsar-1 to Dsar-7) developed dark to olive-brown fast-growing colonies with scarce aerial mycelium after seven days at 25°C on PDA. These isolates showed a dark-olive color on the reverse side of Petri dishes and developed abundant, aggregated, and dark-brown pycnidia after 15 days at 25°C. Conidia were hyaline and aseptate, dark brown, 1-septate, with a brown wall, ovoid with a broadly rounded apex and truncated base, (17.5-) 19.5 ±1.2 (-22.0) x (7.6-) 8.9 ± 0.6 (-10.1) µm (n = 30). These isolates were tentatively identified morphologically as Dothiorella sp. (Phillips et al. 2005). Molecular identification was performed using ITS1/ITS4 and EF1-728F/EF1-986R primers (White et al. 1990; Dissanayake et al. 2015) of the internal transcribed spacer (ITS1-5.8S-ITS2) region and part of the translation elongation factor (EF1-) genes, respectively. A MegaBlast search in GenBank showed a 100% similarity to isolate CBS 115038, the ex-type of Dothiorella sarmentorum. The sequences were added to GenBank (OM161950 to OM161956 for ITS; OM177188 to OM177194 for EF1-). Pathogenicity of two isolates (Dsar-2 and Dsar-7) was tested in the orchard on freshly made pruning wounds on attached branches of 2-year-old-pruned English walnut trees cv. Chandler. A second pathogenicity test was done on freshly made pruning wounds in 1-year-old rooted cuttings (n=15) (40 cm of long) of English walnut cv. Chandler. Each pruning wound was inoculated with 40 µL conidial suspension (105 conidia/mL). Sterile distilled water was used as a control treatment. Both pathogenicity tests were repeated once. After seven months for attached branches and four months for rooted plants, necrotic streaks with a mean length of 81.3 and 44.5 mm were observed below the inoculated pruning wounds, respectively. No necrotic streaks were observed in any of the control wounds. Dothiorella sarmentorum was 100% reisolated from symptomatic tissues of inoculated branches and molecularly identified (EF1-), thus fulfilling Koch's postulates. Recently, D. sarmentorum has been reported causing English walnut dieback in Spain (López-Moral et al. 2020). To our knowledge, this is the first report of D. sarmentorum causing branch dieback of English walnut in Chile. Further studies are needed to know the impact and extent of canker and branch dieback of walnut in commercial orchards in the Maule Region, central Chile.

Severe Outbreak of Dry Core Rot in Apple Fruits cv. Fuji Caused by Kalmusia variispora During Pre-harvest in Maule Region, Chile

Apple (Malus × domestica) is an important fruit crop in Chile, with a cultivated area of 32,313 ha concentrated (63%) in Maule Region (35°25' S). Unusual core rot on 'Fuji' apples was observed at harvest in a commercial orchard in Curicó, Maule Region, with an incidence ranged between 22 to 35% in 2018 and 2019. Previously, in 2017, an incidence of 30% was estimated on 'Fuji' fruits destined to the Asian market. Internal decay symptoms consisted of dry, corky light to dark-brown tissue, within the seed locules initially. In moderate to severe cases, the necrotic lesion progresses deeper into the mesoderm. External symptoms were quite subtle, and typically, the disease goes unnoticed. However, infected fruit ripen earlier. Small pieces (2-3 mm) from the internal lesion margin of symptomatic apples (n = 50) were placed on Potato Dextrose Agar (PDA) (2%) and incubated at 20°C for 10 days. Pure cultures (n = 41) were obtained and transferred to Malt Extract Agar (MEA) (2%). Colonies on MEA produced an even to slight undulating buff margin with white woolly aerial mycelium, and immerse ochreous in the center, changing gray to olivaceous aerial mycelium with age. On the underside, colonies were umber and buff in the center and margin, respectively. After 10 days, numerous densely aggregate dark-brown mature pycnidia were observed. Aseptate conidia were subglobose to cylindrical, straight, and sometimes curved with rounded at both ends, that was initially hyaline to pale olive, thin, smooth wall with mean dimensions of (2.9-) 3.4 (-4.4) x (1.5-) 1.8 (2.2) µm (n=50). Based on morphology, the fungus was identified as Kalmusia variispora (Verkley et al. 2014). The internal transcribed space (ITS), portion of β-tubulin (TUB), and large subunits of the nuclear ribosomal RNA (LSU) loci were used for molecular identification, using primers ITS4/ITS5, Bt2a/Bt2b, and LR0R/LR5 (Ariyawansa et al., 2014). BLAST searches indicated 100% identity with K. variispora (ex-type CBS 121517). The maximum parsimony phylogenetic analysis placed Chilean isolates in the K. variispora clade. Sequences were deposited in GenBank (OL711706 to OL711709, OL739499 to OL739502 and OL711710 to OL711713 for ITS, TUB and LSU, respectively). Pathogenicity tests were conducted using four K. variispora isolates. 'Fuji' apples (n = 20) were surface disinfested (75% ethanol, 30 s) and then wounded and inoculated with conidial suspension (50 L of 106 conidia/mL) deposited in the middle and into the core region using a sterile fine-tipped micropipette. Additionally, 20 one-year dormant rooted cuttings 'Fuji' and 'Cripps Pink' were pruned and immediately inoculated on the pruning wound. An equal number of apples and rooted cuttings treated with sterile water were used as controls. The experiments were repeated once. All inoculated fruits developed lateral lesions (22 to 37 mm) and dry core rot (18 to 36 mm) symptoms identical to those described in the original outbreak, after 20 days at 20°C in a commercial packing box. The inoculated cuttings produced canker lesions of 10 to 21 mm in length, and dieback symptoms were observed after 3 months. No symptoms were observed on the negative controls. Koch's postulates were fulfilled by 100% reisolating K. variispora. Previously, Alternaria spp. have been reported as the primary pathogen associated with moldy core and dry core rot of apples worldwide (McLeod et al., 2014) and in Chile (Elfar et al., 2018). However, Kalmusia spp. have been associated with dry core rot in apples (McLeod et al., 2014) and have been isolated from canker symptoms on apples in Chile (Díaz et al. 2021). To our knowledge, this is the first report of a severe outbreak of K. variispora causing dry core rot in apples in Chile and worldwide.

First Report of Fusarium annulatum Associated with Young Vine Decline in California

From 2018 to 2021 a decline was detected in young vineyards of both wine and table grape (Vitis vinifera L.) in seven counties across California (Kern, Monterey, Napa, Sonoma, Tulare, Yolo, and Yuba). Affected vines showed poor or no growth throughout the season, dieback, sap exudation and internal cankers around the graft union. Lack of feeder roots was detected, indicating weak root development. In some cases, graft failure was associated with the symptomatology in recently established vineyards (<3 years old). A prevalence from 5 to 50% was estimated in 10 vineyards. Affected vines (n=34) were collected by farm advisors and submitted to the laboratory. Symptomatic vines were surface disinfected with 70% ethanol for 1 minute and air dried under sterile conditions. Vascular discoloration around the graft union was observed and inspected by removing the bark using a sterile knife. Isolations were performed from the margin of lesions by placing five wood sections (1×1 mm) per vine onto potato dextrose agar acidified with 0.5 mL/L of 85% lactic acid (APDA) and incubated for 7 days at 25°C in the dark. Even though other fungi associated with young vine decline were isolated and identified as Phaeoacremonium, Ilyonectria, and Botryosphaeriaceae species, Fusarium colonies (Leslie and Summerell, 2006) were the most prevalent among all the symptomatic vines. Pure cultures were obtained by transferring single hyphal tips onto fresh PDA. After 5 days of incubation, colonies formed white aerial mycelium with orange to purple colors on the bottom. Colonies in Spezieller Nährstoffarmer agar (SNA) produced abundant microconidia that were hyaline and ovoid to elliptical, ranging from 5.4 to 10.6 (7.4) × 1.4 to 3.3 (2.4) µm in size (n=50). Straight and slightly curved macroconidia varied from 15.5 to 42.3 (23.7) × 2.6 to 5.0 (3.6) µm in size (n=50). Upon DNA extraction, the translation elongation factor 1α (tef1) and the RNA polymerase II second largest subunit (rpb2) partial gene regions were amplified and sequenced using the EF1/EF2, 5F2/7cR and 7cF/11aR pair primers, respectively (O'Donnell et al. 1998, O'Donnell et al. 2007, Liu et al. 1999). Consensus sequences were compared to the NCBI database using BLAST, showing over 99% similarity with the ex-type sequence of F. annulatum CBS 258.54 (MT010994 and MT010983). A maximum likelihood multi-locus phylogenetic analysis confirmed that all the Californian isolates cluster with F. annulatum strains. Sequences were deposited in GenBank (nos. OK888534 to OK888537). Two representative isolates (UCD9188 and UCD9416) were used for pathogenicity tests. One-year-old 'Chardonnay' vines were inoculated between the second and third node by removing a 5-mm diameter disk of the bark using a sterile cork borer and placing a 5-mm agar plug with actively growing mycelium. Five replicates per isolate including controls with sterile agar plugs were incubated under greenhouse conditions for 2 months. The experiment was performed twice. Symptoms expressed as vascular linear necrotic lesions that ranged from 25.6 to 62.8 mm and the same pathogen was recovered, thus fulfilling Koch's postulates. Fusarium annulatum Bugnic. is a morphologically and genetically diverse species that has been widely known as F. proliferatum and known to be pathogenic in more than 200 plant hosts (Yilmaz et al. 2021). Fusarium spp. have been previously reported to cause young vine decline in Australia and British Columbia, Canada (Highet and Nair, 1995; Úrbez-Torres et al. 2017). To the best of our knowledge, this is the first report of F. annulatum associated with young vine decline complex in California.

Microbial Biocontrol Strategies for Ambrosia Beetles and Their Associated Phytopathogenic Fungi

Ambrosia beetles and their symbiotic fungi are causing severe damage in natural and agro-ecosystems worldwide, threatening the productivity of several important tree crops such as avocado. Strategies aiming at mitigating their impact include the application of broad-spectrum agrochemicals and the incineration of diseased trees, but the increasing demand for environment-friendly strategies call for exploring biological control for the management of ambrosia beetles and their phytopathogenic fungal symbionts. The aim of this review is to examine the existing knowledge on biocontrol approaches using beneficial microorganisms and microbial natural products with entomopathogenic and antifungal activity against ambrosia beetles and fungi. We show that biocontrol has been mainly focused on the insect, using entomopathogenic fungi (EPF) such as Beauveria spp. or Metarhizium spp. However, recent studies have been integrating EPF with mycoparasitic fungi such as Trichoderma spp. to simultaneously challenge the vector and its fungal symbionts. Novel approaches also include the use of microbial natural products as insect lures or antifungal agents. Contrastingly, the potential of bacteria, including actinobacteria (actinomycetes), as biocontrol agents of ambrosia fungi has been little investigated. We thus suggest that future research should further examine the antifungal activity of bacterial strains, with an emphasis on harsh environments. We also suggest pursuing the isolation of more effective microbial strains with dual biocontrol effect, i.e., exhibiting fungicidal/insecticidal activities. Moreover, additional efforts should aim at determining the best application methods of biocontrol agents in the field to ensure that the positive effects detected in vitro are sustained. Finally, we propose the integration of microbiome studies in pest and disease management strategies as they could provide us with tools to steer the beneficial host plant microbiome and to manipulate the beetle microbiome in order to reduce insect fitness.

Phylogenomic Analysis of a 55.1-kb 19-Gene Dataset Resolves a Monophyletic Fusarium that Includes the Fusarium solani Species Complex

Scientific communication is facilitated by a data-driven, scientifically sound taxonomy that considers the end-user's needs and established successful practice. In 2013, the Fusarium community voiced near unanimous support for a concept of Fusarium that represented a clade comprising all agriculturally and clinically important Fusarium species, including the F. solani species complex (FSSC). Subsequently, this concept was challenged in 2015 by one research group who proposed dividing the genus Fusarium into seven genera, including the FSSC described as members of the genus Neocosmospora, with subsequent justification in 2018 based on claims that the 2013 concept of Fusarium is polyphyletic. Here, we test this claim and provide a phylogeny based on exonic nucleotide sequences of 19 orthologous protein-coding genes that strongly support the monophyly of Fusarium including the FSSC. We reassert the practical and scientific argument in support of a genus Fusarium that includes the FSSC and several other basal lineages, consistent with the longstanding use of this name among plant pathologists, medical mycologists, quarantine officials, regulatory agencies, students, and researchers with a stake in its taxonomy. In recognition of this monophyly, 40 species described as genus Neocosmospora were recombined in genus Fusarium, and nine others were renamed Fusarium. Here the global Fusarium community voices strong support for the inclusion of the FSSC in Fusarium, as it remains the best scientific, nomenclatural, and practical taxonomic option available.

Host evolutionary relationships explain tree mortality caused by a generalist pest-pathogen complex

The phylogenetic signal of transmissibility (competence) and attack severity among hosts of generalist pests is poorly understood. In this study, we examined the phylogenetic effects on hosts differentially affected by an emergent generalist beetle-pathogen complex in California and South Africa. Host types (non-competent, competent and killed-competent) are based on nested types of outcomes of interactions between host plants, the beetles and the fungal pathogens. Phylogenetic dispersion analysis of each host type revealed that the phylogenetic preferences of beetle attack and fungal growth were a nonrandom subset of all available tree and shrub species. Competent hosts were phylogenetically narrower by 62 Myr than the set of all potential hosts, and those with devastating impacts were the most constrained by 107 Myr. Our results show a strong phylogenetic signal in the relative effects of a generalist pest-pathogen complex on host species, demonstrating that the strength of multi-host pest impacts in plants can be predicted by host evolutionary relationships. This study presents a unifying theoretical approach to identifying likely disease outcomes across multiple host-pest combinations.

One becomes two: second species of the Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) species complex is established on two Hawaiian Islands

The cryptic species that make up the Euwallacea fornicatus species complex can be readily distinguished via their DNA sequences. Until recently, it was believed that the Hawaiian Islands had been invaded by only one of these cryptic species, E. perbrevis (tea shot hole borer; TSHB). However, following the 2016 deposition of a DNA sequence in the public repository GenBank, it became evident that another species, E. fornicatus (polyphagous shot hole borer; PSHB), had been detected in macadamia orchards on Hawai'i Island (the Big Island). We surveyed the two most-populous islands of Hawai'i, Big Island and O'ahu, and herein confirm that populations of TSHB and PSHB are established on both. Beetles were collected using a variety of techniques in macadamia orchards and natural areas. Individual specimens were identified to species using a high-resolution melt assay, described herein and validated by subsequent sequencing of specimens. It remains unclear how long each species has been present in the state, and while neither is currently recognized as causing serious economic or ecological damage in Hawai'i, the similarity of the newly-confirmed PSHB population to other damaging invasive PSHB populations around the world is discussed. Although the invasive PSHB populations in Hawai'i and California likely have different geographic origins within the beetle's native range, they share identical Fusarium and Graphium fungal symbionts, neither of which have been isolated from PSHB in that native range.

Establishment of a non-native xyleborine ambrosia beetle, Xyleborus monographus (Fabricius) (Coleoptera: Curculionidae: Scolytinae), new to North America in California

Specimens of an ambrosia beetle, Xyleborus monographus (Fabricius), were found infesting oak trees in California. This is the first record of this species established in North America. Based on collection information, this species most likely has been established in the Napa County area for several years. A modified key to Xyleborus in North America, and diagnosis of the species is provided.

Probe-Based Multiplex Real-Time PCR as a Diagnostic Tool to Distinguish Distinct Fungal Symbionts Associated With Euwallacea kuroshio and Euwallacea whitfordiodendrus in California

California has been invaded by two distinct Euwallacea spp. that vector unique plant pathogenic symbiotic fungi on multiple hosts and cause Fusarium dieback. The objective of this study was to develop multiplex real-time quantitative PCR assays using hydrolysis probes targeting the β-tubulin gene to detect, distinguish, and quantify fungi associated with the polyphagous shot hole borer (PSHB; Euwallacea whitfordiodendrus, Fusarium euwallaceae, Graphium euwallaceae, and Paracremonium pembeum) as well as the Kuroshio shot hole borer (KSHB; Euwallacea kuroshio, Fusarium kuroshium, and Graphium kuroshium) from various sample types. Absolute quantification reaction efficiencies ranged from 88.2 to 104.3%, with a coefficient of determination >0.992 and a limit of detection of 100 copies µl^-1 for all targets across both assays. Qualitative detection using the real-time assays on artificially inoculated avocado shoot extracts showed more sensitivity compared with conventional fungal isolation from wood. All symbiotic fungi, except P. pembeum, from PSHB and KSHB female heads were detectable and quantified. Field samples from symptomatic Platanus racemosa, Populus spp., and Salix spp. across 17 of 26 city parks were positively identified as PSHB and KSHB through detection of their symbiotic fungi, and both were found occurring together on five trees from three different park locations. The molecular assays presented here can be utilized to accurately identify fungi associated with these invasive pests in California.

Identification, Pathogenicity, and Spore Trapping of Colletotrichum karstii Associated with Twig and Shoot Dieback in California

Colletotrichum Corda, 1831 species are well-documented pathogens of citrus that are associated with leaf and fruit anthracnose diseases. However, their role in twig and shoot dieback diseases of citrus has recently become more prominent. Recent surveys of orchards in the Central Valley of California have revealed C. gloeosporioides and a previously undocumented species, C. karstii, to be associated with twig and shoot dieback. Pathogenicity tests using clementine (cv. 4B) indicated that both C. karstii and C. gloeosporioides are capable of producing lesions following inoculation of citrus stems. Pathogenicity tests also revealed C. karstii to be the most aggressive fungal species producing the longest lesions after 15 months. The majority of spores trapped during this study were trapped during or closely following a precipitation event with the majority of spores being trapped from January through May. These findings confirm C. karstii as a new pathogen of citrus in California.

Evaluation of Emamectin Benzoate and Propiconazole for Management of a New Invasive Shot Hole Borer (Euwallacea nr. fornicatus, Coleoptera: Curculionidae) and Symbiotic Fungi in California Sycamores

The polyphagous shot hole borer (Euwallacea nr. fornicatus, Coleoptera: Curculionidae: Scolytinae), an exotic and invasive ambrosia beetle, was recently found attacking a number of tree species in Los Angeles, Orange, Riverside, and San Diego Counties in southern California. Their colonization and subsequent inoculation of a suite of symbiotic fungi that cause Fusarium Dieback, has resulted in extensive mortality of some tree species, including, California sycamore (Platanus racemose Nutt.). There are no sustainable control options for polyphagous shot hole borer other than maintaining tree vigor and removal of severely infested host material. The effectiveness of therapeutic treatments of an injected systemic insecticide containing emamectin benzoate (EB) alone and in combination with a systemic fungicide, propiconazole (P), was evaluated over a 4-yr period for maintaining the health of individual sycamore trees infested by polyphagous shot hole borer. All treatments containing EB reduced levels of polyphagous shot hole borer colonization and associated sap flow at attack sites compared to untreated controls. A second trial evaluated preventative treatments of EB and P alone or combined to protect individual sycamore from colonization by polyphagous shot hole borer. After 45 mo posttreatment, all treatments significantly reduced polyphagous shot hole borer attack levels and successful attacks compared to untreated controls (EB + P > EB alone > P alone). We concluded that EB alone or combined with P are acceptable therapeutic and preventative treatments for management of polyphagous shot hole borer in California sycamore in southern California.

Avocado rhizobacteria emit volatile organic compounds with antifungal activity against Fusarium solani, Fusarium sp. associated with Kuroshio shot hole borer, and Colletotrichum gloeosporioides

Recent studies showed that bacterial volatile organic compounds (VOCs) play an important role in the suppression of phytopathogens. The ability of VOCs produced by avocado (Persea americana Mill.) rhizobacteria to suppress the growth of common avocado pathogens was therefore investigated. We evaluated the antifungal activity of VOCs emitted by avocado rhizobacteria in a first screening against Fusarium solani, and in subsequent antagonism assays against Fusarium sp. associated with Kuroshio shot hole borer, Colletotrichum gloeosporioides and Phytophthora cinnamomi, responsible for Fusarium dieback, anthracnosis and Phytophthora root rot in avocado, respectively. We also analyzed the composition of the bacterial volatile profiles by solid phase microextraction (SPME) gas chromatography coupled to mass spectrometry (GC-MS). Seven isolates, belonging to the bacterial genera Bacillus and Pseudomonas, reduced the mycelial growth of F. solani with inhibition percentages higher than 20%. Isolate HA, related to Bacillus amyloliquefaciens, significantly reduced the mycelial growth of Fusarium sp. and C. gloeosporioides and the mycelium density of P. cinnamomi. Isolates SO and SJJ, also members of the genus Bacillus, reduced Fusarium sp. mycelial growth and induced morphological alterations of fungal hyphae whilst isolate HB, close to B. mycoides, inhibited C. gloeosporioides. The analysis of the volatile profiles revealed the presence of ketones, pyrazines and sulfur-containing compounds, previously reported with antifungal activity. Altogether, our results support the potential of avocado rhizobacteria to act as biocontrol agents of avocado fungal pathogens and emphasize the importance of Bacillus spp. for the control of emerging avocado diseases such as Fusarium dieback.

The Protean Acremonium. A. sclerotigenum/egyptiacum: Revision, Food Contaminant, and Human Disease

Acremonium is known to be regularly isolated from food and also to be a cause of human disease. Herein, we resolve some sources of confusion that have strongly hampered the accurate interpretation of these and other isolations. The recently designated type species of the genus Acremonium, A. alternatum, is known only from a single isolate, but it is the closest known relative of what may be one of the planet's most successful organisms, Acremonium sclerotigenum/egyptianum, shown herein to be best called by its earliest valid name, A. egyptiacum. The sequencing of ribosomal internal transcribed spacer (ITS) regions, actin genes, or both for 72 study isolates within this group allowed the full range of morphotypes and ITS barcode types to be elucidated, along with information on temperature tolerance and habitat. The results showed that nomenclatural confusion and frequent misidentifications facilitated by morphotaxonomy, along with misidentified early sequence deposits, have obscured the reality that this species is, in many ways, the definitive match of the historical concept of Acremonium: a pale orange or dull greenish-coloured monophialidic hyphomycete, forming cylindrical, ellipsoidal, or obovoid conidia in sticky heads or obovoid conidia in dry chains, and acting ecologically as a soil organism, marine organism, plant pathogen, plant endophyte, probable insect pathogen, human opportunistic pathogen, food contaminant, probable dermatological communicable disease agent, and heat-tolerant spoilage organism. Industrially, it is already in exploratory use as a producer of the antibiotic ascofuranone, active against trypanosomes, cryptosporidia, and microsporidia, and additional applications are in development. The genus-level clarification of the phylogeny of A. egyptiacum shows other historic acremonia belong to separate genera, and two are here described, Parasarocladium for the Acremonium radiatum complex and Kiflimonium for the Acremonium curvulum complex.

Chemical Management of Invasive Shot Hole Borer and Fusarium Dieback in California Sycamore (Platanus racemosa) in Southern California

Fusarium dieback (FD) is a new vascular disease of hardwood trees caused by Fusarium spp. and other associated fungal species which are vectored by two recently introduced and highly invasive species of ambrosia beetle (Euwallacea spp. nr. fornicatus). One of these ambrosia beetles is known as the polyphagous shot hole borer (PSHB) and the other as the Kuroshio shot hole borer (KSHB). Together with the fungi that they vector, this pest-disease complex is known as the shot hole borer-Fusarium dieback (SHB-FD) complex. Mitigation of this pest-disease complex currently relies on tree removal; however, this practice is expensive and impractical given the wide host range and rapid advancement of the beetles throughout hardwoods in southern California. This study reports on the assessment of various pesticides for use in the management of SHB-FD. In vitro screening of 13 fungicides revealed that pyraclostrobin, trifloxystrobin, and azoxystrobin generally have lower effective concentration that reduces 50% of mycelial growth (EC₅₀) values across all fungal symbionts of PSHB and KSHB; metconazole was found to have lower EC₅₀ values for Fusarium spp. and Paracremonium pembeum. Triadimefon and fluxapyroxad were not capable of inhibiting any fungal symbiont at the concentrations tested. A 1-year field study showed that two insecticides, emamectin benzoate alone and in combination with propiconazole, and bifenthrin, could significantly reduce SHB attacks. Two injected fungicides (tebuconazole and a combination of carbendazim and debacarb) and one spray fungicide (metconazole) could also significantly reduce SHB attacks. Bioassays designed to assess fungicide retention 1 year postapplication revealed that six of the seven fungicides exhibited some level of inhibition in vitro and all thiabendazole-treated trees sampled exhibiting inhibition. This study has identified several pesticides which can be implemented as part of an integrated pest management strategy to reduce SHB infestation in low to moderately infested landscape California sycamore trees and potentially other landscape trees currently affected by SHB-FD.

Two Novel Fungal Symbionts Fusarium kuroshium sp. nov. and Graphium kuroshium sp. nov. of Kuroshio Shot Hole Borer (Euwallacea sp. nr. fornicatus) Cause Fusarium Dieback on Woody Host Species in California

Shot hole borer (SHB)-Fusarium dieback (FD) is a new pest-disease complex affecting numerous tree species in California and is vectored by two distinct, but related ambrosia beetles (Euwallacea sp. nr. fornicatus) called polyphagous shot hole borer (PSHB) and Kuroshio shot hole borer (KSHB). These pest-disease complexes cause branch dieback and tree mortality on numerous wildland and landscape tree species, as well as agricultural tree species, primarily avocado. The recent discovery of KSHB in California initiated an investigation of fungal symbionts associated with the KSHB vector. Ten isolates of Fusarium sp. and Graphium sp., respectively, were recovered from the mycangia of adult KSHB females captured in three different locations within San Diego County and compared with the known symbiotic fungi of PSHB. Multigene phylogenetic analyses of the internal transcribed spacer region (ITS), translation elongation factor-1 alpha (TEF1-α), and RNA polymerase II subunit (RPB1, RPB2) regions as well as morphological comparisons revealed that two novel fungal associates Fusarium kuroshium sp. nov. and Graphium kuroshium sp. nov. obtained from KSHB were related to, but distinct from the fungal symbionts F. euwallaceae and G. euwallaceae associated with PSHB in California. Pathogenicity tests on healthy, young avocado plants revealed F. kuroshium and G. kuroshium to be pathogenic. Lesion lengths from inoculation of F. kuroshium were found to be significantly shorter compared with those caused by F. euwallaceae, while no difference in symptom severity was detected between Graphium spp. associated with KSHB and PSHB. These findings highlight the pest disease complexes of KSHB-FD and PSHB-FD as distinct, but collective threats adversely impacting woody hosts throughout California.

Evaluations of Insecticides and Fungicides for Reducing Attack Rates of a new invasive ambrosia beetle (Euwallacea Sp., Coleoptera: Curculionidae: Scolytinae) in Infested Landscape Trees in California

A recently discovered ambrosia beetle with the proposed common name of polyphagous shot hole borer (Euwallacea sp., Coleoptera: Curculionidae: Scolytinae), is reported to attack >200 host tree species in southern California, including many important native and urban landscape trees. This invasive beetle, along with its associated fungi, causes branch dieback and tree mortality in a large variety of tree species including sycamore (Platanus racemosa Nutt.). Due to the severity of the impact of this Euwallacea sp., short-term management tools must include chemical control options for the arboriculture industry and private landowners to protect trees. We examined the effectiveness of insecticides, fungicides, and insecticide-fungicide combinations for controlling continued Euwallacea sp. attacks on previously infested sycamore trees which were monitored for 6 mo after treatment. Pesticide combinations were generally more effective than single pesticide treatments. The combination of a systemic insecticide (emamectin benzoate), a contact insecticide (bifenthrin), and a fungicide (metconazole) provided some level of control when applied on moderate and heavily infested trees. The biological fungicide Bacillus subtilis provided short-term control. There was no difference in the performance of the three triazole fungicides (propiconazole, tebuconazole, and metconazole) included in this study. Although no pesticide combination provided substantial control over time, pesticide treatments may be more effective when trees are treated during early stages of attack by this ambrosia beetle.

PCR Multiplexes Discriminate Fusarium Symbionts of Invasive Euwallacea Ambrosia Beetles that Inflict Damage on Numerous Tree Species Throughout the United States

Asian Euwallacea ambrosia beetles vector Fusarium mutualists. The ambrosial fusaria are all members of the ambrosia Fusarium clade (AFC) within the Fusarium solani species complex (FSSC). Several Euwallacea-Fusarium mutualists have been introduced into nonnative regions and have caused varying degrees of damage to orchard, landscape, and forest trees. Knowledge of symbiont fidelity is limited by current identification methods, which typically requires analysis of DNA sequence data from beetles and the symbionts cultured from their oral mycangia. Here, polymerase chain reaction (PCR)-based diagnostic tools were developed to identify the six Fusarium symbionts of exotic Euwallacea spp. currently known within the United States. Whole-genome sequences were generated for representatives of six AFC species plus F. ambrosium and aligned to the annotated genome of F. euwallaceae. Taxon-specific primer-annealing sites were identified that rapidly distinguish the AFC species currently within the United States. PCR specificity, reliability, and sensitivity were validated using a panel of 72 Fusarium isolates, including 47 reference cultures. Culture-independent multiplex assays accurately identified two AFC fusaria using DNA isolated from heads of their respective beetle partners. The PCR assays were used to show that Euwallacea validus is exclusively associated with AF-4 throughout its sampled range within eastern North America. The rapid assay supports federal and state agency efforts to monitor spread of these invasive pests and mitigate further introductions.

Identification, Distribution, and Pathogenicity of Diatrypaceae and Botryosphaeriaceae Associated with Citrus Branch Canker in the Southern California Desert

Several members of the families Botryosphaeriaceae and Diatrypaceae are known as canker and dieback pathogens of a number of woody hosts. Because desert citrus production in California can occur in proximity to table grape production, it was suspected that fungi associated with grapevine cankers might also be associated with citrus branch canker and dieback decline. To determine the fungi associated with branch canker and dieback disease of citrus in the southern California desert regions, surveys were conducted from 2011 to 2013 in the major citrus-growing regions of Riverside, Imperial, and San Diego Counties. Cankered tissues were collected from branches showing symptoms typical of branch canker and dieback. Various fungal species were recovered from necrotic tissues and species were identified morphologically and by phylogenetic comparison of partial sequences of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2), β-tubulin gene, and elongation factor 1-α genes with those of other species in GenBank. Four fungi, including Neoscytalidium hyalinum, Eutypella citricola, E. microtheca, and an unnamed Eutypella sp., were associated with branch canker. N. hyalinum was the most frequently recovered fungus from symptomatic tissues (31%) followed by E. citricola (10%), E. microtheca (4%), and the Eutypella sp. (2%). In pathogenicity tests, all fungi caused lesions when inoculated on 'Lisbon' lemon (citrus) branches. Lesions caused by the Eutypella sp. were significantly longer than those of the other Eutypella spp.; however, they did not differ significantly from those produced by N. hyalinum. The most-parsimonious unrooted trees based on the combined data of ITS and partial β-tubulin gene region sequences showed three distinct clades of Eutypella spp. (E. citricola, E. microtheca, and an unidentified Eutypella sp.). Similarly, ITS and partial translation elongation factor 1-α gene region sequences differentiated two species of Neoscytalidium, N. hyalinum and N. novaehollandiae. Identifying the diversity, distribution, and occurrence of these fungal pathogens is useful for the management of citrus branch canker and dieback disease in the desert citrus-growing regions of California.

Discordant phylogenies suggest repeated host shifts in the Fusarium-Euwallacea ambrosia beetle mutualism

The mutualism between xyleborine beetles in the genus Euwallacea (Coleoptera: Curculionidae: Scolytinae) and members of the Ambrosia Fusarium Clade (AFC) represents one of 11 known evolutionary origins of fungiculture by ambrosia beetles. Female Euwallacea beetles transport fusarial symbionts in paired mandibular mycangia from their natal gallery to woody hosts where they are cultivated in galleries as a source of food. Native to Asia, several exotic Euwallacea species were introduced into the United States and Israel within the past two decades and they now threaten urban landscapes, forests and avocado production. To assess species limits and to date the evolutionary diversification of the mutualists, we reconstructed the evolutionary histories of key representatives of the Fusarium and Euwallacea clades using maximum parsimony and maximum likelihood methods. Twelve species-level lineages, termed AF 1-12, were identified within the monophyletic AFC and seven among the Fusarium-farming Euwallacea. Bayesian diversification-time estimates placed the origin of the Euwallacea-Fusarium mutualism near the Oligocene-Miocene boundary ∼19-24 Mya. Most Euwallacea spp. appear to be associated with one species of Fusarium, but two species farmed two closely related fusaria. Euwallacea sp. #2 in Miami-Dade County, Florida cultivated Fusarium spp. AF-6 and AF-8 on avocado, and Euwallacea sp. #4 farmed Fusarium ambrosium AF-1 and Fusarium sp. AF-11 on Chinese tea in Sri Lanka. Cophylogenetic analyses indicated that the Euwallacea and Fusarium phylogenies were largely incongruent, apparently due to the beetles switching fusarial symbionts (i.e., host shifts) at least five times during the evolution of this mutualism. Three cospeciation events between Euwallacea and their AFC symbionts were detected, but randomization tests failed to reject the null hypothesis that the putative parallel cladogenesis is a stochastic pattern. Lastly, two collections of Euwallacea sp. #2 from Miami-Dade County, Florida shared an identical cytochrome oxidase subunit 1 (CO1) allele with Euwallacea validus, suggesting introgressive hybridization between these species and/or pseudogenous nature of this marker. Results of the present study highlight the importance of understanding the potential for and frequency of host-switching between Euwallacea and members of the AFC, and that these shifts may bring together more aggressive and virulent combinations of these invasive mutualists.

First Report of Geosmithia pallida Causing Foamy Bark Canker, a New Disease on Coast Live Oak (Quercus agrifolia), in Association with Pseudopityophthorus pubipennis in California

Declining coast live oak (Quercus agrifolia) trees have been observed since 2012 throughout urban landscapes in Los Angeles, Orange, Riverside, Santa Barbara, Ventura, and Monterey counties in California. Symptoms causing branch dieback and tree death included a cinnamon-colored gum seeping through multiple 0.95-mm-diameter entry holes on the bole, followed by a prolific, cream-colored foamy liquid. Beneath the outer bark was phloem and xylem necrosis. Fifty 1- to 2.5-mm adult and larval beetles were collected. Adults fit the morphological description of Pseudopityophthorus pubipennis (western oak bark beetle) (R. Rabaglia, personal communication), and ~800 bp of the mitochondrial COI gene was amplified for three beetles using primer pairs and methods previously described (2,3). All three sequences were identical (GenBank Accession Nos. KJ831289 to 91) and a BLAST search confirmed the closest match (94%) as P. pubipennis. Necrotic wood tissues collected from two trees in each county were cultured on potato dextrose agar amended with 0.01% tetracycline (PDA-tet), and incubated at 25°C for 1 week. Ochre-colored cultures with plane or radially furrowed velutinous mycelium were consistently produced. Fifty conidia each measured from two isolates were 3.66 ± 0.04 μm × 1.77 ± 0.03 μm, and arranged in non-persistent conidial chains, at first roughly parallel, becoming tangled with age. These fungal colonies were observed within gallery walls. The rDNA internal transcribed spacer (ITS) was amplified using primer pairs and methods previously described (5). Three isolates were sequenced and matched 100% to known sequences of Geosmithia pallida in GenBank; sequences of two isolates (UCR2208 and UCR2210) were deposited in GenBank (KJ468687 and KJ468688). Pathogenicity tests were performed by inoculating twelve 27.0-cm detached coast live oak shoots for each isolate with a spore suspension of G. pallida (UCR2208 and UCR2210) and sterile distilled water for controls. A 2-mm-wide, 3-mm-deep hole was drilled into the center of each shoot, 20 μl of a 10⁶ conidia/ml spore suspension was pipetted into the hole, and sealed with Vaseline and Parafilm. The experiment was repeated twice. After 4 weeks in a moist chamber at 25°C, lesions produced by G. pallida averaged 8.3 cm and was significantly longer (ANOVA; P < 0.0001) from the control (average 0.4 cm). G. pallida was re-isolated from all inoculated plants and identified by colony morphology. P. pubipennis is a native beetle, common as a secondary agent, and previously not associated with disease. However, cryptic species may be common among bark and ambrosia beetles (4). A larger sample (i.e., populations and loci) is needed to determine the precise taxonomic status of P. pubipennis. G. pallida was shown to inhibit root growth of Q. petraea by 25% in Europe (1), appears to have affinities with a range of subcorticolous insects, and is widely distributed (5), but there is no published record of the fungus occurring in the United States. This is the first report of G. pallida causing foamy bark canker in association with P. pubipennis on Q. agrifolia in California. Results suggest this new disease complex is causing decline of Q. agrifolia throughout the state. References: (1) D. Cizková et al. Folia Microbiol. 50:59, 2005. (2) A. I. Cognato and F. A. H. Sperling. Mol. Phylogenet. Evol. 14:445, 2000. (3) A. I. Cognato et al. Mol. Phylogenet. Evol. 36:494, 2006. (4) B. H. Jordal and M. Kambestad. Mol. Ecol. Res. 14:7, 2014. (5) M. Kolarík et al. Mycol. Res. 108:1053, 2004.

First Report of Diaporthe neoviticola Associated with Wood Cankers of Grapevine in Turkey

In recent years, delayed bud bursting, cane bleaching, shoot dieback, and cankers in 1-year-old canes and perennial arms were observed in vineyards of the Aegean region (western Turkey). These symptoms were frequently observed on the following major table grape (Vitis vinifera) cultivars: 'Alphonse Lavallée,' 'Cardinal,' 'Sultana Seedless,' and 'Trakya Ilkeren' in 2012. To determine the causal agents, symptomatic woody tissues (0.5 cm²) were sampled from the canes of nine Manisa and four Salihli Cities (13 total) grapevine varieties and were plated onto potato dextrose agar amended with tetracycline (0.01%) (PDA-tet). A considerable amount of phomopsis-like fungi were isolated from the symptomatic tissues and fungal colonies were incubated for 2 to 3 weeks to induce sporulation. After incubation for 14 days at 24°C in the dark, white mycelial growth with undulating colony margins, and abundant pycnidia producing hyaline, ellipsoidal, fusoid α-conidia with invisible nuclei, and β-conidia, were observed on PDA, and they resembled species in the Diaporthaceae (1,2). The α-conidia dimensions were 9.3 to 10.2 × 1.9 to 2.9 μm (avg. 9.7 × 2.4 μm) and β-conidia were 19 to 24 × 0.5 to 1 μm (avg. 22 × 0.9 μm). For molecular identification, fungal DNA was extracted from mycelial mats and ribosomal DNA fragments (ITS1, 5.8S ITS2 rDNA, amplified with ITS4 and ITS5 primers) (3) were sequenced and the sequences were compared with those deposited in NCBI GenBank in a BLASTn search. The representative isolate (MBAi43AG) showed 99% homology with Diaporthe neoviticola isolate from New Zealand KC145831.1. The DNA sequence of the identified isolate was submitted to GenBank under accession number KF460427. Pathogenicity tests were conducted under controlled conditions (24°C, 16/8 h day/night, and 70% RH) on 1-cm-diameter, detached green grapevine cv. Cabernet Sauvignon canes (with leaves) using the isolate of D. neoviticola specified above. The shoots were wounded by creating a 5-mm-diameter incision with a sterile scalpel. An agar disc with mycelia and pycniospores was placed into each wound and covered with Parafilm. Sterile PDA plugs were used as mock inoculum for the control plants. There were 10 replicates per treatment and the experiment was repeated twice. After 1 month of incubation, the green shoots were examined for the extent of superficial blackish lesions. The average lesion length on inoculated shoots was 18.2 mm for D. neoviticola. No lesions were observed in the control shoots. The fungal isolate was successfully re-isolated from 96% of inoculated shoots to fulfill Koch's postulates. To our knowledge, this is the first report of D. neoviticola causing wood canker and dieback of shoots on grapevine in Turkey. References: (1) R. R. Gomes. Persoonia 31:1, 2013. (2) D. Udayanga et al. Fungal Diversity 56:157, 2012. (3) J. M. van Niekerk et al. Australas. Plant Pathol. 34:27, 2005.

First Report of Wood Canker Caused by Botryosphaeria dothidea, Diplodia seriata, Neofusicoccum parvum, and Lasiodiplodia theobromae on Grapevine in Turkey

The Aegean region (western Turkey) is the center of table, raisin, and wine grape cultivation. During the 2012 growing season, wood canker symptoms were observed in vineyards in Manisa city. Symptoms adjacent to pruning wounds, including shoot dieback and wedge-shaped wood discolorations observed in cross section, were among the most prevalent symptoms of the vines. To identify the causal agents, symptomatic woody tissues were surface disinfested with 95% ethanol and flame-sterilized and the discolored outer bark was cut away. The internal tissues (0.5 cm²) were excised from cankers of vines and plated onto potato dextrose agar amended with tetracycline (0.01%) (PDA-tet). The most frequently isolated fungi, based on general growth pattern, speed of growth, and colony color, resembled species in the Botryosphaeriaceae family. According to morphological characteristics, four different groups have been identified based on visual discrimination. After DNA extraction, ribosomal DNA fragments (ITS1-5.8S-ITS2) (2) amplified with ITS4 and ITS5 primers were sequenced and sequences were compared with those deposited in NCBI GenBank database. Four different Botryosphaeriaceae isolates were identified, including Botryosphaeria dothidea (MBAi25AG), Diplodia seriata (MBAi23AG), Lasiodiplodia theobromae (MBAi28AG), and Neofusicoccum parvum (MBAi27AG) (Accession Nos. KF182329, KF182328, KF182331, and KF182330, respectively) with species nomenclature based on Crous et al. (1). Pathogenicity tests were conducted under greenhouse conditions (24°C, 16/8-h day/night, 70% RH) on 1-year-old own rooted grapevine (Vitis vinifera) cv. Sultana Seedless seedlings using one isolate from each of the Botryosphaeriaceae species specified above. Stems of grapevine seedlings were wounded by removing bark with 4-mm cork borer and fresh mycelial plugs were inoculated into the holes and covered with Parafilm. Sterile PDA plugs were placed into the wounds of control seedlings. Five vines were inoculated per isolate. The experiment was repeated twice. After 4 months of incubation, grapevine seedlings were examined for the extent of vascular discoloration and recovery of fungal isolates. Mean lesion lengths on wood tissues were 85.3, 17.2, 13.9, and 13.1 mm for N. parvum, B. dothidea, L. theobromae, and D. seriata, and 6.3 mm for control. Each fungal isolate was successfully re-isolated from inoculated seedlings to fulfill Koch's postulates. To our knowledge, this is the first report of multiple species in the Botryosphaeriaceae causing wood canker and dieback on grapevine in Turkey. These results are significant because Botryosphaeriaceae species are known causal agents of grapevine trunk disease worldwide (3). References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) B. Slippers et al. Mycologia 96:83, 2004. (3) J. R. Urbez-Torres. Phytopathol. Mediterr. 50:S5, 2011.

Identification of Species of Botryosphaeriaceae Causing Bot Gummosis in Citrus in California

Members of the Botryosphaeriaceae family are known to cause Bot gummosis on many woody plants worldwide. To identify pathogens associated with Bot gummosis on citrus in California, scion and rootstock samples were collected in 2010 and 2011 from five citrus-growing counties in California. Symptoms observed on citrus included branch cankers, dieback, and gumming. Various fungal species were recovered from necrotic tissues of branch canker and rootstock samples. Species were identified morphologically and by phylogenetic comparison as 'Eureka' lemon, 'Valencia', 'Washington Navel', 'Fukumoto', grapefruit, 'Satsuma', and 'Meyer' lemon. Species were identified morphologically and by phylogenetic comparison of the complete sequence of the internal transcribed spacer regions, β-tubulin gene, and elongation factor α-1 genes with those of other species in GenBank. A consensus-unrooted most parsimonious tree resulting from multigene phylogenetic analysis showed the existence of three major clades in the Botryosphaeriaceae family. In total, 74 isolates were identified belonging to the Botryosphaeriaceae family, with Neofusicoccum spp., Dothiorella spp., Diplodia spp., (teleomorph Botryosphaeria), Lasiodiplodia spp., and Neoscytalidium dimidiatum (teleomorphs unknown) accounting for 39, 25, 23, 10, and 3% of the total, respectively. On inoculated Eureka lemon shoots, lesion length was significantly different (P < 0.05) among 14 isolates recovered from portions of cankered tissues of the original trees. Lesion lengths were significantly longer (P < 0.05) for shoots inoculated with isolates of Neofusicoccum luteum and shorter for shoots inoculated with isolates of Dothiorella viticola (P < 0.05) than those of other species. Identifying the distribution and occurrence of these fungal pathogens associated with Bot gummosis is useful for management applications during occasional outbreaks in California.

Identification and Pathogenicity of Fungal Pathogens Associated with Stem-End Rot of Avocado in California

Stem-end rot of harvested avocado fruit commonly occurs wherever the crop is cultivated. Multiple fungal species have been described as causal agents. To determine the causal pathogens of stem-end rot in California, fungal isolations were conducted from symptomatic fruit, and fungi were identified by morphological and molecular techniques. In 2010 and 2011, a total of 177 isolates were recovered from 290 avocado fruit collected from seven orchards in one of the major avocado growing areas in Southern California. The majority of isolates was identified as Neofusicoccum luteum (65%), with the remainder either as Colletotrichum gloeosporioides (33%) or Phomopsis sp. (2%). In a pathogenicity test, N. luteum caused significantly (P < 0.05) more severe stem-end rot than either C. gloeosporioides or Phomopsis sp. No significant (P > 0.05) differences in stem-end rot severity were observed between inoculations with N. luteum isolated from fruit stem-end rot and N. luteum or N. parvum isolated from branch cankers. This confirms that stem-end rot of avocado can be initiated by fungi causing branch cankers. Although low humidity and rainfall during much of the growing and harvest seasons in California are considered unfavorable conditions for the development of avocado stem-end rot, the identification of the causal pathogens is of value when decays have to be managed during outbreaks, and it stresses the importance of managing branch cankers.

First Report of Wood Canker Caused by Neoscytalidium dimidiatum on Grapevine in California

In May 2012 in the Coachella valley, Riverside County, California, the decline of vines in table grape (Vitis vinifera) vineyards was observed. Foliar symptoms consisted of shoot blight with wilting and necrosis of leaves and drying and shriveling of berries. In some cases, the entire vine collapsed in the middle of the growing season (apoplexia). Wood cankers in the spurs, cordons, and trunks of affected vines were also present. The nine isolates recovered from the cankers were identified as Neoscytalidium dimidiatum (Penz.) Crous & Slippers based on morphological characteristics and DNA sequence comparisons. Two isolates were grown on potato dextrose agar (PDA) medium and a total of 50 conidia were measured per isolate. Conidia were ellipsoid to ovoid, with a truncate base and an acutely rounded apex, initially aseptate, becoming brown and two-celled at maturity, 7.2 ± 1.2 μm × 3.8 ± 0.4 μm. The rDNA internal transcribed spacer (ITS), and β-tubulin (BT) loci were amplified using primer pairs and methods previously described (4). A total of five isolates were sequenced. The DNA sequences of one N. dimidiatum grapevine isolate (UCR-Neo1) were deposited in the GenBank database (ITS, KC937066; BT, KC937067). Pathogenicity tests were performed by inoculating 12 grape cuttings cv. Thompson Seedless with isolate UCR-Neo1 and 12 control cuttings with sterile medium using a technique previously described (1). The experiment was repeated twice. After 20 weeks of incubation period in the greenhouse, the lesions length produced by N. dimidiatum averaged 13.5 mm and was significantly longer (P < 0.05) from the control (average 3 mm). N. dimidiatum was reisolated from all the inoculated plants and identified by colony morphology. The incidence of N. dimidiatum in table grape vineyards of the Coachella valley has been estimated at 15%, with nine vines infected out of 60 vines total. This pathogen has been identified in California in walnut nursery causing the death of trees due to the development of canker at the graft union (2). N. dimidiatum has also been identified as the causal agent of shoot blight, canker, and gummosis on citrus in Italy (3). The crop is also being grown in the Coachella valley and these findings warrant further investigation in order to determine the host range, distribution, and incidence of this pathogen in the area. References: (1) K. Baumgartner et al. Plant Dis. 97:912, 2013. (2) S. F. Chen et al. Plant Dis. 97:993, 2013. (3) G. Polizzi et al. Plant Dis 93:1215, 2009. (4) J. R. Urbez-Torres et al. Plant Dis. 92:519, 2008.

First Report of Togninia minima Perithecia on Esca- and Petri-Diseased Grapevines in South Africa

Esca and petri diseases are important grapevine trunk diseases in South Africa and most other grape-producing countries. The causal pathogens are Phaeomoniella chlamydospora and several species of Phaeoacremonium. In total, 25 species of Phaeoacremonium have been isolated from grapevines of which seven species have been linked to Togninia teleomorphs obtained through in vitro mating studies (3). Of these species, only perithecia of T. minima, T. fraxinopennsylvanica, and T. viticola have been found on grapevines in California (1,2,4). T. minima is heterothallic, and although both mating types are present in South African vineyards, perithecia have never been observed (3). In the current study, grapevine cordons and trunks were collected from vineyards and rootstock mother vines within Western Cape Province for examination in the laboratory under a dissecting microscope. The grapevines displayed general decline symptoms, including reduced vegetative growth, dead or dying shoots and cordons, as well as internal vascular streaking and/or a red/black/brown margin next to decayed wood typically associated with esca and petri disease. Rootstock mother vines were apparently healthy, although many old, cracked pruning wounds were visible. Togninia-like perithecia with distinctive long necks were found along the wood crevices, often on old pruning wounds. The perithecia were removed and placed on microscope slides with sterile water. Structures were measured and slides were washed with 500 μl of sterile water onto potato dextrose agar amended with chloramphenicol (250 mg/liter). Ascospores were allowed to germinate overnight to obtain single ascospore colonies. Perithecia were found on cultivars Muscat d' Alexandrie and Pinotage (Vitis vinifera) at Stellenbosch in May 2011 and on Ramsey (V. champinii) rootstock mother vines at Slanghoek in June 2012. Perithecia were globose to subglobose, black, and often embedded in the wood tissue but also present on the surface of the wood. The length of the necks was 250 to 300 × 47.5 to 55 μm. The asci were hyaline and ranged from 16 to 25 × 3.5 to 5 μm. Ascospores were hyaline, ellipsoid, and ranged from 5 to 6 × 1.5 to 2 μm. These measurements were similar to those reported by Mostert et al. (3) and Rooney et al. (4). Colony growth was typical of T. minima. DNA was extracted from the colonies and the partial betatubulin gene was amplified and sequenced using the primers T1 and Bt2b. Sequences were deposited into GenBank (JX962864 to 67). Based on a megablast search of the NCBI's GenBank nucleotide database, 100% similarity was found with other T. minima sequences (JQ691670.1, HQ605018.1, HQ605014.1; identities = 647/647 [100%], gaps = 0/647 [0%]). To our knowledge, this is the first report on the occurrence of T. minima perithecia on grapevines in Western Cape Province of South Africa. The removal of dead spurs and cordons will be instrumental in lowering the inoculum originating from perithecia, especially in rootstock mother blocks where no control strategies are applied for petri disease or esca. Spore trapping studies are currently in progress to study spore release patterns in order to determine whether pruning wounds are at risk during traditional pruning periods. References: (1) A. Eskalen et al. Plant Dis. 89:528, 2005. (2) A. Eskalen et al. Plant Dis. 89:686, 2005. (3) L. Mostert et al. Stud. Mycol. 54:1, 2006. (4) S. Rooney-Latham et al. Plant Dis. 89:867, 2005.

Fusarium euwallaceae sp. nov.--a symbiotic fungus of Euwallacea sp., an invasive ambrosia beetle in Israel and California

The invasive Asian ambrosia beetle Euwallacea sp. (Coleoptera, Scolytinae, Xyleborini) and a novel Fusarium sp. that it farms in its galleries as a source of nutrition causes serious damage to more than 20 species of live trees and pose a serious threat to avocado production (Persea americana) in Israel and California. Adult female beetles are equipped with mandibular mycangia in which its fungal symbiont is transported within and from the natal galleries. Damage caused to the xylem is associated with disease symptoms that include sugar or gum exudates, dieback, wilt and ultimately host tree mortality. In 2012 the beetle was recorded on more than 200 and 20 different urban landscape species in southern California and Israel respectively. Euwallacea sp. and its symbiont are closely related to the tea shot-hole borer (E. fornicatus) and its obligate symbiont, F. ambrosium occurring in Sri Lanka and India. To distinguish these beetles, hereafter the unnamed xyleborine in Israel and California will be referred to as Euwallacea sp. IS/CA. Both fusaria exhibit distinctive ecologies and produce clavate macroconidia, which we think might represent an adaption to the species-specific beetle partner. Both fusaria comprise a genealogically exclusive lineage within Clade 3 of the Fusarium solani species complex (FSSC) that can be differentiated with arbitrarily primed PCR. Currently these fusaria can be distinguished only phenotypically by the abundant production of blue to brownish macroconidia in the symbiont of Euwallacea sp. IS/CA and their rarity or absence in F. ambrosium. We speculate that obligate symbiosis of Euwallacea and Fusarium, might have driven ecological speciation in these mutualists. Thus, the purpose of this paper is to describe and illustrate the novel, economically destructive avocado pathogen as Fusarium euwallaceae sp. nov. S. Freeman et al.

Identification of New Fungal Pathogens of Coast Live Oak in California

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 β-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.

Host Range of Fusarium Dieback and Its Ambrosia Beetle (Coleoptera: Scolytinae) Vector in Southern California

The polyphagous shot hole borer (PSHB) is an invasive ambrosia beetle that forms a symbiosis with a new, as-yet-undescribed Fusarium sp., together causing Fusarium dieback on avocado and other host plants in California and Israel. In California, PSHB was first reported on black locust in 2003 but there were no records of fungal damage until 2012, when a Fusarium sp. was recovered from the tissues of several backyard avocado trees infested with PSHB in Los Angeles County. The aim of this study was to determine the plant host range of the beetle-fungus complex in two heavily infested botanical gardens in Los Angeles County. Of the 335 tree species observed, 207 (62%), representing 58 plant families, showed signs and symptoms consistent with attack by PSHB. The Fusarium sp. was recovered from 54% of the plant species attacked by PSHB, indicated by the presence of the Fusarium sp. at least at the site of the entry hole. Trees attacked by PSHB included 11 species of California natives, 13 agriculturally important species, and many common street trees. Survey results also revealed 19 tree species that function as reproductive hosts for PSHB. Additionally, approximately a quarter of all tree individuals planted along the streets of southern California belong to a species classified as a reproductive host. These data suggest the beetle-disease complex potentially may establish in a variety of plant communities locally and worldwide.

Effect of Fungicide Application on the Management of Avocado Branch Canker (Formerly Dothiorella Canker) in California

Members of the Botryosphaeriaceae family have been associated with branch cankers of avocado trees (Persea americana) in California. Canker infections are initiated by spores entering the host plant through fresh wounds such as pruning wounds. With high-density planting becoming more common in the California avocado industry, more intensive pruning may increase the occurrence of branch canker. The objective of this study was to evaluate the preventive ability of some commercial fungicides belonging to different chemical families against fungal pathogens associated with avocado branch canker. Initially, 12 fungicides were tested in vitro for their effect on the inhibition of mycelial growth of three isolates of Dothiorella iberica and isolates (five per species) of Neofusicoccum australe, N. luteum, N. parvum, and Phomopsis sp. Subsequently, azoxystrobin, fludioxonil, metconazole, and pyraclostrobin, selected because of their low effective concentrations that reduce 50% of mycelial growth (EC₅₀ values), and myclobutanil, selected for its high EC₅₀ value, were tested in two field experiments. Azoxystrobin and fludioxonil were used in a premix with propiconazole and cyprodinil, respectively, in field trials. Significant differences (P < 0.05) were observed among fungicides in field trials. Azoxystrobin + propiconazole had the highest percent inhibition at 52 and 62% (internal lesion length) in trial 1 and trial 2, respectively, although this level of inhibition was not significantly different from that of metconazole. A significant correlation (r = 0.51, P < 0.05) was observed between internal lesion length data in the field experiment and EC₅₀ data from in vitro fungicide screening. Application of azoxystrobin + propiconazole and metconazole can play a key role in protecting Californian avocado against fungi causing avocado branch canker.

An inordinate fondness for Fusarium: phylogenetic diversity of fusaria cultivated by ambrosia beetles in the genus Euwallacea on avocado and other plant hosts

Ambrosia beetle fungiculture represents one of the most ecologically and evolutionarily successful symbioses, as evidenced by the 11 independent origins and 3500 species of ambrosia beetles. Here we document the evolution of a clade within Fusarium associated with ambrosia beetles in the genus Euwallacea (Coleoptera: Scolytinae). Ambrosia Fusarium Clade (AFC) symbionts are unusual in that some are plant pathogens that cause significant damage in naïve natural and cultivated ecosystems, and currently threaten avocado production in the United States, Israel and Australia. Most AFC fusaria produce unusual clavate macroconidia that serve as a putative food source for their insect mutualists. AFC symbionts were abundant in the heads of four Euwallacea spp., which suggests that they are transported within and from the natal gallery in mandibular mycangia. In a four-locus phylogenetic analysis, the AFC was resolved in a strongly supported monophyletic group within the previously described Clade 3 of the Fusarium solani species complex (FSSC). Divergence-time estimates place the origin of the AFC in the early Miocene ∼21.2 Mya, which coincides with the hypothesized adaptive radiation of the Xyleborini. Two strongly supported clades within the AFC (Clades A and B) were identified that include nine species lineages associated with ambrosia beetles, eight with Euwallacea spp. and one reportedly with Xyleborus ferrugineus, and two lineages with no known beetle association. More derived lineages within the AFC showed fixation of the clavate (club-shaped) macroconidial trait, while basal lineages showed a mix of clavate and more typical fusiform macroconidia. AFC lineages consisted mostly of genetically identical individuals associated with specific insect hosts in defined geographic locations, with at least three interspecific hybridization events inferred based on discordant placement in individual gene genealogies and detection of recombinant loci. Overall, these data are consistent with a strong evolutionary trend toward obligate symbiosis coupled with secondary contact and interspecific hybridization.

Spore Trapping and Pathogenicity of Fungi in the Botryosphaeriaceae and Diaporthaceae Associated with Avocado Branch Canker in California

Avocado branch canker in California is caused by a complex of fungal species in the families Botryosphaeriaceae and Diaporthaceae. As the popularity of avocado fruit increases, California growers are under pressure to increase their productivity in order to compete with imports. One way to increase production is through high-density planting, which entails intense canopy management, possibly leaving the trees vulnerable to infection through pruning wounds. A spore trap study was undertaken to determine the seasonal spore discharge of Botryosphaeriaceous and Diaporthaceous fungi. Based on colony counts, the highest population of Botryosphaeriaceous fungi (68%) occurred during or soon after precipitation events, which coincided with the winter months of December, January, and February. The spring and fall seasons had lower numbers of spores trapped (at 13 and 17%, respectively), with few spores trapped in the summer season. For members of the Diaporthaceae family, spores trapped were almost evenly split between winter and fall seasons (50 and 49%, respectively), with few to no spores trapped in the spring and summer seasons. A pathogenicity test of six fungi of Botryosphaeriaceae and one fungus of Diaporthaceae was conducted in the greenhouse. Internal plant vascular lesion lengths resulting from inoculation with any of the seven fungal species differed significantly from the noninoculated control. These studies suggest that pruning during the drier parts of the year would minimize infection by fungi in the Botryosphaeriaceae and Diaporthaceae families.

First Report of a Fusarium sp. and Its Vector Tea Shot Hole Borer (Euwallacea fornicatus) Causing Fusarium Dieback on Avocado in California

Per capita consumption of avocado in the United States has nearly doubled between 2000 and 2010. The California avocado industry supplies almost 40% of U.S. demand and the remaining 60% is supplied by imports from Latin America and New Zealand. The Tea Shot Hole Borer (TSHB) is an ambrosia beetle from Asia that forms a symbiosis with a new, yet undescribed Fusarium sp. and is a serious problem for the Israeli avocado industry (3). The beetle also causes severe damage on the branches of tea (Camelia sinensis) in Sri Lanka and India (1). In California, TSHB was first reported on black locust (Robinia pseudoacacia) in 2003, but there are no records of fungal damage (4). In 2012, nine backyard avocado trees (cvs. Hass, Bacon, Fuerte, and Nabal) exhibiting branch dieback were observed throughout the residential neighborhoods of South Gate, Downey, and Pico Rivera in Los Angeles County. Upon inspection, symptoms of white powdery exudate, either dry or surrounded by wet discoloration of the outer bark in association with a single beetle exit hole, were found on the trunk and main branches of the tree. Examination of the cortex and wood under the exit hole revealed brown discolored necrosis. The TSHB was also found within galleries that were 1 to 4 cm long going against the grain. Symptomatic cortex and sapwood tissues were plated onto potato dextrose agar amended with 0.01% tetracycline (PDA-tet). The TSHB was dissected and plated onto PDA-tet after surface disinfestation following methods described by Kajimura and Hijii (2). After 5 days of incubation at room temperature, regular fungal colonies with aerial mycelia and reddish brown margins were produced. Single spore isolations were used to establish pure culture of the fungus. Fifty conidia were hyaline, clavate with a rounded apex, and initially aseptate (4.1 to 12.0 × 2.4 to 4.1 μm) becoming one- to three-septate (7.6 to 15.1 × 2.8 to 4.5 μm, 9.2 to 17.2 × 3.4 to 4.8 μm, and 13.5 to 17.6 × 4.3 to 4.7 μm, respectively). Identity of the fungal isolates was determined by amplification of the rDNA genes with primers ITS4/5 and EF1/2, respectively. Sequences were deposited into GenBank under Accession Nos. JQ723753, JQ723760, JQ723756, and JQ723763. A BLASTn search revealed 100% similarity to Fusarium sp. (Accession Nos. JQ038020 and JQ038013). Detached green shoots of healthy 1-year-old avocado were wounded to a depth of 1 to 2 mm and 5-mm mycelial plugs from 5-day-old cultures (UCR 1781 and UCR 1837) were placed mycelial side down onto the freshly wounded surfaces and then wrapped with Parafilm. Control shoots were inoculated with sterile agar plugs and five replicates per treatment were used. Shoots were incubated at 25 ± 1°C in moist chambers for 3 weeks. Lesions were observed on all inoculated shoots except for the control. Mean lesion lengths were 10.7 and 12.8 cm for UCR1781 and UCR1837, respectively, and were significantly different (P ≤ 0.05) from the control. Both isolates were reisolated from 100% of symptomatic tissues of inoculated shoots to complete Koch's postulates. This experiment was conducted twice and similar results were obtained. To our knowledge, this is the first report of Fusarium sp. and its vector E. fornicatus causing Fusarium dieback on Avocado in California. References: (1) W. Danthanarayana. Tea Quarterly 39:61, 1968. (2) H. Kajimura and N. Hijii. Ecol. Res. 7:107, 1992; (3) Mendel et al., Phytoparasitica, DOI 10.1007/s12600-012-0223-7, 2012. (4) R. J. Rabaglia. Annals Entomol. Soc. Amer. 99:1034, 2006.

First Report of Multiple Species of the Botryosphaeriaceae Causing Bot Canker Disease of Indian Laurel-Leaf Fig in California

Indian laurel-leaf fig (Ficus microcarpa L.) is a commonly used indoor and outdoor ornamental tree. F. microcarpa is most frequently encountered as lining city streets, especially in warmer southern California climates. A disease known as 'Sooty Canker,' caused by the fungus Nattrassia mangiferae (Syd. & P. Syd) B. Sutton & Dyko, is particularly devastating on F. microcarpa. Disease symptoms are characterized by branch dieback, crown thinning, and if the disease progresses to the trunk, eventual tree death (2). Recent taxonomic revisions have renamed Nattrassia mangiferae as Neofusicoccum mangiferae (Syd. & P. Syd.) Crous, Slippers & A. J. L. Phillips (1). An initial survey conducted during the spring of 2011 across four cities in Los Angeles County included, Culver City, Lakewood, Santa Monica, and Whittier. Five symptomatic branches per city were collected from trees showing branch cankers and dieback. Pieces of symptomatic tissue (2 mm²) were plated onto one-half-strength potato dextrose agar. Most isolates initially identified by morphological characteristics, such as growth pattern, speed of growth, and colony color, resembled those in the Botryosphaeriaceae (4). Two representative isolates from each site location were sequenced. Sequences obtained from amplification of the internal transcribed spacer region (ITS1-5.8rDNA-ITS2) and the β-tubulin gene were compared in a BLAST search in GenBank. Results identified isolates as Botryosphaeria dothidea (identity of 99% to EF638767 and 100% to JN183856.1 for ITS and β-tubulin, respectively); Neofusicoccum luteum (100% to EU650669 and 100% to HQ392752); N. mediterraneum (100% to HM443605 and 99% to GU251836); and N. parvum (100% to GU188010 and 100% to HQ392766) and have been deposited in GenBank with the following accession numbers: JN543668 to JN543671 (ITS) and JQ080549 to JQ080552 (β-tubulin). Pathogenicity tests were conducted in the greenhouse on 6-month-old F. microcarpa with one isolate from each previously listed fungal species. Five plants per isolate were stem-wound inoculated with mycelial plugs and wrapped with Parafilm. Uncolonized agar plugs were used as a control. Inoculations were later repeated a second time in the same manner for a total of 10 plants per isolate. Plants were observed for 6 weeks and destructively sampled to measure vascular lesion lengths. Mean vascular lesion lengths were 26, 22, 54, and 46 mm for B. dothidea, N. luteum, N. mediterraneum, and N. parvum, respectively. The mean lesion lengths for all isolates were significantly different (P = 0.05) from the control. Each species was consistently recovered from inoculated plants, except the control, thus fulfilling Koch's postulates. To our knowledge, this is the first report on the pathogenicity of multiple Botryosphaeriaceae species causing branch canker and dieback on F. microcarpa in California. These results are significant since trees along sidewalks in southern California are often crowded and undergo extensive root and branch pruning and some Botryosphaeriaceae spp. are known to enter its host through wounds caused by pruning or mechanical injury (2,3). Further sampling is imperative to better assess the distribution of these canker-causing fungal pathogens on F. microcarpa. References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) D. R. Hodel et al. West. Arborist 35:28, 2009. (3) V. McDonald et al. Plant Dis. 93:967, 2009. (4) B. Slippers et al. Fungal Biol. Rev. 21:90, 2007.

Botryosphaeriaceae Species Associated with Avocado Branch Cankers in California

Members of the family Botryosphaeriaceae cause branch cankers and dieback on California avocado trees. More intensive pruning, a practice associated with high-density planting that is becoming more common in the California avocado industry, may increase the occurrence of branch canker. This study was undertaken to identify and characterize the Botryosphaeriaceae spp. involved in the branch canker disease complex in order to develop future management strategies. From 2008 to 2009, branch cankers were sampled from four or five trees from each of eight avocado groves in five California counties. Six Botryosphaeriaceae spp. were identified based on morphology as well as phylogenetic analysis of the internal transcribed spacer region (ITS1-5.8S-ITS2) and a partial sequence of the β-tubulin gene. These six species included Neofusicoccum australe, N. luteum, N. parvum, an unknown Neofusicoccum sp., Fusicoccum aesculi, and Dothiorella iberica. Members of the Botryosphaeriaceae were isolated from all avocado-growing regions sampled in California; however, incidence and distribution of species varied. This report is the first description of the isolation of D. iberica from avocado branch cankers in California.

First Report of Eutypella spp. Associated with Branch Canker of Citrus in California

Eutypella is one of the few genera in the Diatrypaceae considered plant pathogens (1). In California, E. vitis and other members of the Diatrypaceae cause branch and trunk canker on grapevine (3,4). Eutypella spp. have not previously been documented as pathogens of citrus. In a 2010 survey on citrus branch canker and dieback in six citrus-growing counties of California, four isolates of Eutypella species were detected in Riverside and San Diego counties. Canker symptoms included dieback and bark cracking, and cuts made through symptomatic trees showed that the cankers were expanding through the center of the tree. Branch samples were collected from 10 trees per orchard and 5 to 10 orchards per county (102 trees for two counties). Pieces of symptomatic tissue (1 to 2 mm²) were plated onto potato dextrose agar amended with 0.01% tetracycline (PDA-tet) and incubated at 25°C for 4 days. All isolates were identified by morphological and molecular characteristics. PCR of isolates was performed in a thermal cycler using two primer pairs, ITS4/5 and Bt2a/2b for amplifying the internal transcribed spacer (ITS1), 5.8S, and ITS2 region and the β-tubulin gene, respectively (2,3). PCR products were sequenced at the University of California, Riverside Genomics Core and the sequences compared in a BLAST search. Four isolates identified as Eutypella spp. included two (UCR1088 and UCR1101) from San Diego County and two (UCR1148 and UCR1149) from the Riverside County samples. The sequences were deposited in GenBank (HQ880579, JF758610, HQ880581, and HQ880582 and HQ880583, JF758611, HQ880585, and HQ880586 for the ITS regions and β-tubulin gene, respectively. ITS sequences for UCR1088 and UCR1101 had 98 and 100% match, respectively, to Eutypella spp. ITS sequences in GenBank (GQ293959 to GQ293961), while UCR1148 and UCR1149 matched 99% (GQ293956 to GQ293958). On the basis of morphological characteristics, UCR1088 and UCR1101 were similar to Eutypella spp. group 1, while UCR1148 and UCR1149 were similar to Eutypella spp. group 3 (4). Pathogenicity tests were conducted with all four isolates on detached shoots from healthy citrus trees of the same cultivar/rootstock from which each isolate was obtained. One wound per shoot was made on 1-year-old, green, detached shoots using a 3-mm-diameter cork borer and the wounded surfaces were inoculated with 3-mm-diameter mycelial plugs of 5-day-old cultures of each isolate growing on PDA-tet. Inoculated wounds and shoot ends were covered with petroleum jelly and wrapped with Parafilm (3). Control shoots were inoculated with sterile agar plugs. There were 10 inoculated shoots per isolate and noninoculated control treatment. Shoots were incubated at 25°C in moist chambers for 6 weeks. Lesions similar to those on the original infected shoots were observed on all inoculated shoots except the control treatment. Reisolation and identification of fungi from inoculated and control shoots were done using methods described above. Inoculated isolates were recovered from 100% of inoculated shoots but none was recovered from noninoculated shoots, indicating association of Eutypella spp. with citrus branch canker. To our knowledge, this is the first report of Eutypella spp. associated with cankers on citrus in California. References: (1) B. Piskur et al. Plant Dis. 91:1579, 2007. (2) B. Slippers et al. Mycologia 96:83, 2004. (3) F. P. Trouillas and W. D. Gubler. Plant Dis. 94:867, 2010. (4) F. P. Trouillas et al. Mycologia 102:319, 2010.

First Report of Raffaelea canadensis Causing Laurel Wilt Disease Symptoms on Avocado in California

Laurel wilt disease is a newly described vascular disease of redbay (Persea borbonia (L.) Spreng.) and other members of the Lauraceae family in the southeastern United States. The disease, caused by the fungus Raffaelea lauricola and vectored by a nonnative redbay ambrosia beetle (Xyleborus glabratus Eichhoff), was first detected in Georgia in 2003 (1). Laurel wilt has caused extensive mortality of native redbay in Georgia, Florida, South Carolina, and recently, Mississippi. The avocado, Persea americana, is in the Lauraceae family and has been shown to be susceptible to the laurel wilt pathogen in Florida (3). The potential spread of this pathogen into California is of concern to the commercial avocado industry. During a survey in 2010 in a Temecula, CA avocado orchard with a history of root rot, an avocado (cv. Hass) tree with a diameter at breast height (DBH) of 45 cm was found to be showing typical laurel wilt disease symptoms. The crown was approximately 80% declined and exhibited dead branches without leaves. Black-to-brown discolored sapwood under the bark and many ambrosia beetle exit holes within 1 to 1.5 m up the bole were also observed. A Raffaelea sp. was consistently isolated from symptomatic branch tissue (from two different branches) plated onto cycloheximide-streptomycin malt agar (2) and incubated at room temperature for 2 weeks. Small subunit (18S) sequences of rDNA (approximately 1,150 bp) of three Raffaelea isolates were amplified using primers NS1 and NS4 (4) and deposited into GenBank under Accession Nos. JF327799, JF327800, and JF327801. A BLASTn search of all three sequences revealed high homology (98, 99, and 98% respectively) to an accession of R. canadensis associated with a species of ambrosia beetle (GenBank Accession No. AY858665). Pathogenicity testing was conducted by pipetting 50 μl of a 10⁵ conidia per ml suspension of each of two isolates (UCR1080 and UCR1081) into five 2-mm-diameter holes on each of two avocado (cv. Hass) trees (10 to 15 cm DBH). Isolate UCR1080 was inoculated into three holes on Tree 1 and two holes on Tree 2. Isolate UCR1081 was inoculated into two holes on Tree 1 and three holes on Tree 2. Sterile water was used as a control in five 2-mm-diameter holes on each tree. Holes were drilled to the cambium within 1 to 2 m up the bole using a 0.157-cm electric drill. Four months later, phloem tissue was peeled back, lesion lengths were measured, and pieces of necrotic tissue were cultured for completion of Koch's postulates. R. canadensis was consistently reisolated from necrotic tissue but not from control treatments. To our knowledge, this is the first report of R. canadensis associated with wilt on avocado in California. R. canadensis is closely related to R. lauricola, however, its impact on the California avocado industry is unknown at this time. References: (1) S. W. Fraedrich et al. Plant Dis. 92:215, 2008. (2) T. C. Harrington et al. Mycotaxon 111:337, 2010. (3) A. E. Mayfield et al. Plant Dis. 92:976, 2008. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

First Report of Spencermartinsia viticola, Neofusicoccum australe, and N. parvum Causing Branch Canker of Citrus in California

Dothiorella gummosis and canker on citrus is generally viewed as a minor disease but can result in serious decline of trees. Symptoms, mostly found on branches, include grayish-to-brown cast on cankered bark, which can extend into the xylem. Dothiorella gummosis was earlier believed to be caused by Dothiorella gregaria (2). In a continuing survey on citrus in six California counties (Fresno, Riverside, San Diego, San Luis Obispo, Tulare, and Ventura) in 2010, branch cankers were collected. Small pieces of symptomatic tissues were plated onto potato dextrose agar amended with 0.01% tetracycline (PDA-tet) and incubated at 25°C for 4 days. Fungi most frequently isolated were initially identified as Botryosphaeriaceae based on morphological characters (1,3). Total genomic DNA was PCR amplified with primers Bt2a/2b for the β-tubulin (BT); EF1-728F/986R for the elongation factor α-1 (EF); and ITS4/5 for the internal transcribed spacer ITS1-5.8S-ITS2 regions (3). Sequences were compared in a BLAST search. Spencermartinsia viticola UCP105 was isolated from cv. Parent Washington on Sour Orange rootstock in Tulare County, Neofusicoccum australe UCR1110 from cv. Satsuma in Riverside County, and N. parvum UCR1166 from cv. Meyer Lemon on Volkameriana rootstock in Ventura County. Sequences of UCP105, UCR1110, and UCR1166 have been deposited in GenBank under Accession Nos. JF271766, JF271776, and JF271780 for BT; JF271784, JF271793, and JF271796 for EF; and JF271748, JF271758, and JF271762 for the ITS regions. The sequences matched with isolates in GenBank as follows: ITS region of strain UCP105-98% match with Accession Nos. AY905556-8; BT of strain UCR1110-99% with GU251879-80; and EF of strain UCR1166-98% with GU251238. Pathogenicity tests were conducted by inoculating green shoots of healthy citrus trees similar to cultivar/rootstock from which each isolate was obtained. Fresh wounds were made on 1-year-old citrus shoots with a 3-mm cork borer, and the freshly wounded surfaces were inoculated with 3-mm mycelial plugs from 5-day-old cultures on PDA-tet. Control shoots were inoculated with sterile agar plugs and each treatment had 10 replicates. Inoculated wounds and shoot ends were covered with petroleum jelly and wrapped with Parafilm to prevent desiccation. Shoots were incubated at 25°C in moist chambers for 4 weeks. Lesions were observed on all inoculated shoots except for the control. Mean lesion lengths were 6.4, 7.0, and 6.9 cm for UCP105, UCR1110, and UCR1166, respectively, which were significantly (P = 0.05) different from the control (0.8 cm). The three isolates were reisolated from symptomatic tissues of inoculated shoots to confirm their pathogenicity. This test was repeated and similar results were obtained. Results indicate that there are multiple species in the Botryosphaeriaceae family causing symptoms on citrus that were previously believed to be caused by D. gregaria. To our knowledge, this is the first report of S. viticola, N. australe, and N. parvum on citrus in California. References: (1) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (2) V. McDonald et al. Plant Dis. 93:967, 2009. (3) B. Slippers et al. Mycologia 96:83, 2004.

First Report of Bot Canker Caused by Diplodia corticola on Coast Live Oak (Quercus agrifolia) in California

Sharp decline and mortality of coast live oak (Quercus agrifolia) has been observed in San Diego County, CA since 2002. Much of this decline has been attributed to a new pest in California, the goldspotted oak borer (GSOB, Agrilus coxalis) (1). Symptoms include crown thinning, bark cracking and/or peeling, patches of stain (1 to 10 cm in diameter), bleeding on the bole, and tree death and are most often observed on trees with a diameter at breast height (DBH) >30 cm. In 2008, a Botryosphaeria sp. was recovered from necrotic tissue of bleeding bole cankers from GSOB-affected trees in Jamul, CA. Zone lines separated dead and live tissue in affected phloem and xylem. Pycnidia were observed on the bark surface of the infected host. Fifty conidia averaging 32 × 18 μm, one-septate with age, and morphologically similar to conidia described by Úrbez-Torres et al. were observed (4). Oak stands with tree mortality were surveyed in GSOB-infested and -uninfested sites over eight locations throughout San Diego and Riverside counties in 2009 and 2010. Symptomatic tissue or conidia from pycnidia of affected trees, plated onto potato dextrose agar amended with 0.01% tetracycline and incubated at 25°C for 1 week, consistently produced cultures with dense, wooly, olive-green mycelium. Mycelia fit the description of Botryosphaeria corticola A.J.L. Phillips, Alves et Luque (anamorph Diplodia corticola) (2). The resulting amplified ITS4/5 region of two sequences matched 100% to published D. corticola sequences (GU799472 and GU799460) (4). These sequences were deposited with NCBI GenBank (HM104176 and HM104177). Koch's postulates were conducted by inoculating 2-mm-diameter holes on five coast live oak trees with D. corticola. Holes were drilled to the cambium at 2 to 4 locations per tree within 1 to 2 m up the bole using a 0.157-cm portable electric drill. Trees ranged from 3.7- to 32.4-cm DBH. Either single agar plugs from two isolates each of a 7-day-old culture (UCR454 and UCR793) or noncolonized agar plugs as uninoculated controls were inserted into the holes and then covered with petroleum jelly and Parafilm. Average temperature was 10°C, relative humidity of 64%, and no precipitation during inoculation. Inoculations were conducted at a location in San Diego County uninfested by GSOB and repeated twice. After 3.5 months, bark was removed from inoculation sites. Average lesion length was not significantly different between inoculations, thus data were combined (one way analysis of variance [ANOVA]; P = 0.05). Lesions averaged 13.9 × 2.3 cm and were significantly different (n = 30; one way ANOVA; P = 0.05) from controls that measured 0.31 × 0.3 cm. Staining was observed around the inoculation points on all trees and three trees exhibited bleeding. Necrotic tissue was observed in the phloem and 3 mm into the xylem tissue, where the lesion had extended up and down the grain. D. corticola was consistently reisolated from necrotic tissue but not from control treatments. B. corticola was originally described as a canker pathogen on Quercus spp. in the western Mediterranean (2), and is known to contribute to the decline of cork oak (Q. suber) in the region (3). To our knowledge, this is the first report of D. corticola causing bot canker on coast live oak in California. References: (1) T. W. Coleman and S. J. Seybold. U. S. For. Serv. R5-PR-08, 2008. (2) A. Correia et al. Mycologia 96:598, 2004. (3) J. Luque et al. For. Pathol. 38:147, 2008. (4) J. R. Úrbez-Torres et al. Plant Dis. 94:785, 2010.