Search

Tomato brown rugose fruit virus (ToBRFV) is a tobamovirus that was first detected in Israel and Jordan following an outbreak of a new disease infecting tomato in 2014. Since then, the virus has been reported from all continents except Oceania and Antarctica. In response to the first finding of the virus in The Netherlands, the Dutch National Plant Protection Organization created a ToBRFV Nextstrain build (v1). In this report, we announce 47 new (near) complete ToBRFV genomes and the generation of the new ToBRFV Nextstrain (v2) build containing 118 ToBRFV genomes with associated geographic and epidemiological data. Examples of utilization of the genomic sequences are presented, and we report the first sequence from South America and present a novel hypothesis on the possible ToBRFV center of origin. [Formula: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

Photinia (Photinia × fraseri Dress) is a well-known green plant that has high ornamental value and is widely distributed around the world. An outbreak of typical bud blight disease was observed between May and August in photinia in 2017 in Qingdao, China. The causal agent for this blight was subsequently isolated from symptomatic samples and identified as Nothophoma quercina based on morphological characterization and molecular analyses (ITS, LSU, RPB2, and TUB2). Results of pathogenicity tests on isolated fungi also supported the conclusion that N. quercina is the pathogen responsible for this condition. To our knowledge, this is the first report of bud blight on P. fraseri caused by N. quercina in China.

Forest diseases caused by invasive fungal pathogens are becoming more common, sometimes with dramatic consequences to forest ecosystems. The development of early detection systems is necessary for efficient surveillance and to mitigate the impact of invasive pathogens. Windborne spores are an important pathway for introduction of fungal pathogens into new areas; the design of spore trapping devices adapted to forests, capable of collecting different types of spores, and aligned with development of efficient molecular methods for detection of the pathogen, should help forest managers anticipate new disease outbreaks. Two types of Rotorod samplers were evaluated for the collection of airborne inoculum of forest fungal pathogens with a range of spore sizes in five forest types. Detection was by specific quantitative PCR (qPCR) and by high-throughput sequencing (HTS) of amplified internal transcribed spacer sequences using a new bioinformatic pipeline, FungiSearch, developed for diagnostic purposes. Validation of the pipeline was conducted on mock communities of 10 fungal species belonging to different taxa. Although the sensitivity of the new HTS pipeline was lower than the specific qPCR, it was able to detect a wide variety of fungal pathogens. FungiSearch is easy to use, and the reference database is updatable, making the tool suitable for rapid identification of new pathogens. This new approach combining spore trapping and HTS detection is promising as a diagnostic tool for invasive fungal pathogens.

International audience; Blast disease is a notorious fungal disease leading to dramatic yield losses on major food crops such as rice and wheat. The causal agent, Pyricularia oryzae, encompasses different lineages, each having a different host range. Host shifts are suspected to have occurred in this species from Setaria spp. to rice and from Lolium spp. to wheat. The emergence of blast disease on maize in Iran was observed for the first time in the north of the country in 2012. We later identified blast disease in two additional regions of Iran: Gilan in 2013 and Golestan in 2016. Epidemics on the weed barnyard grass (Echinochloa spp.) were also observed in the same maize fields. Here, we showed that P. oryzae is the causal agent of this disease on both hosts. Pathogenicity assays in the greenhouse revealed that strains from maize can infect barnyard grass and conversely. However, genotyping with simple sequence repeat markers and comparative genomics showed that strains causing field epidemics on maize and on barnyard grass are different, although they belong to the same previously undescribed clade of P. oryzae. Phylogenetic analyses including these strains and a maize strain collected in Gabon in 1985 revealed two independent host-range expansion events from barnyard grass to maize. Comparative genomics between maize and barnyard grass strains revealed the presence or absence of five candidate genes associated with host specificity on maize, with the deletion of a small genomic region possibly responsible for adaptation to maize. This recent emergence of P. oryzae on maize provides a case study to understand host range expansion. Epidemics on maize raise concerns about potential yield losses on this crop in Iran and potential geographic expansion of the disease.

Tar spot of corn is a fairly new disease to the United States, and since its introduction in 2015 it has spread to over 310 counties across nine states. Little is understood of the biology and epidemiology of the causative agent of tar spot of corn, Phyllachora maydis. Published research from Latin America indicates that spores can only travel a distance of 75 m; however, rapid progression and spread in the United States, in addition to widespread observations of top-down infection, indicate distal dispersal is likely more important. We observed an isolated plot of decorative corn in an urban setting, isolated from agricultural fields. We assessed nearby fields for crop, tar spot, cropping history, and distance from the urban site. Based on our observations, the propagules infecting the urban plot arrived from at least 560 m if from corn residue, and from at least 1,249 m if from active infections from nearby corn. Although this observation is not replicated, it does indicate that dispersal values from Latin America may not reflect the potential dispersion in Midwest topographies.

Wilting of branches and leaves was observed on 4-5 year old apple trees of the varieties Delicious and Fuji in orchards located in Wushan, Gansu Province, China in April 2018. Subsequently, the ste...

Acer palmatum Thunb. is an important colorful leaf ornamental tree species widely distributed in Japan, Korea and China (Carlos et al. 2016). In October 2019, powdery mildew was observed on leaves ...

Acer pictum subsp. mono (Maxim.) H. Ohashi is a common deciduous tree species that is widely distributed in Northeast and Northern China, including all provinces of the Yangtze River Basin (Liu et ...

Big-leaf mahogany (Swietenia macrophylla) is valued for its high-quality wood and use in urban landscapes in Mexico. During surveys of mango-producing areas in the central western region of Mexico, symptoms of malformation, the most important disease of mango in the area, were observed on big-leaf mahogany trees. The objectives of this research were to describe this new disease and determine its cause. Symptoms on big-leaf mahogany at four sites in Michoacán, Mexico resembled those of the vegetative phase of mango malformation, including compact, bunched growth of apical and lateral buds, with greatly shortened internodes and small leaves that curved back toward the supporting stem. Of 163 isolates that were recovered from symptomatic tissues, most were identified as Fusarium pseudocircinatum (n = 121) and F. mexicanum (n = 39) using molecular systematic data; two isolates represented unnamed phylospecies within the F. incarnatum-equiseti species complex (FIESC 20-d and FIESC 37-a) and another was in the F. solani species complex (FSSC 25-m). However, only F. mexicanum and F. pseudocircinatum induced malformation symptoms on 14-day-old seedlings of big-leaf mahogany. The results indicate that F. mexicanum and F. pseudocircinatum, previously reported in Mexico as causal agents of mango malformation disease, also affect big-leaf mahogany. This is the first report of this new disease and the first time that F. mexicanum was shown to affect a host other than mango.

Leaf and neck anthracnose caused by Colletotrichum coccodes is a new disease of onion in Michigan. To test the effect of inoculation method, Prince onion seedlings were grown in the greenhouse and inoculated with either a conidial suspension of C. coccodes (alone or with an abrasive agent) or infested millet seed (dry or wet, 2 or 5 g). Foliar disease severity was greater when a conidial suspension (>39%) was used compared with infested millet seed (≤24.3%). Growth chamber studies were conducted using Infinity onion seedlings that were inoculated with a conidial suspension spray to determine the effects of temperature (15, 20, 25, or 30°C) and duration (0, 12, 24, 48, or 72 h) of high (95 ± 5%) relative humidity (RH) on disease severity (percentage of leaf area with C. coccodes lesions). Significant differences and interactions among temperature and RH were observed. The combination of high temperature (≥25°C) and extended (≥24 h) high RH resulted in >20% disease severity 28 days postinoculation. Results suggest that onion leaf and neck anthracnose symptoms are likely to be more severe when the environmental conditions are ≥25°C with ≥24 h of high RH.

Epimediums (Epimedium grandiflorum) are popular perennial groundcovers and are known to produce a wide range of medicinal effects. Extracts have long been used in traditional Chinese medicine. Carnation ringspot virus (CRSV) has a wide host range. In 2018, symptoms were observed on epimedium in three different landscape settings across St. Paul, MN. Leaf symptoms consisted of conspicuous mottling, chlorotic ringspots, and distortion of leaf margins. CRSV was confirmed by reverse transcription polymerase chain reaction. The CRSV host range now includes epimedium, which is the first species of the Berberidaceae family shown to be susceptible to CRSV. The potential risk of infection in other ornamental plant species in the family should be evaluated.

Emerging plant diseases frequently have significant economic, environmental, cultural, and social impacts. The prediction of new disease emergence, associated with new pathogens or not, remains a difficult and controversial topic. The main factors driving epidemics are often only identified several years after outbreaks, generally revealing that a limited number of factors are associated with the emergence of specific groups of pathogens. This pattern is illustrated in the insect-borne xylem-limited bacterium Xylella fastidiosa, an organism associated with several new plant diseases in different regions of the globe. Research during the last decade focusing on several severe disease outbreaks has led to substantial changes in our understanding of X. fastidiosa biology, ecology, and evolution. This new information has not only led to new insights into aspects of the biology of this bacterium and its interactions with plant and insect hosts, but also made available a phylogenetic framework that has allowed for better inferences concerning factors leading to the emergence of diseases. Here we identify and discuss these main pathways leading to epidemics caused by X. fastidiosa. Our ultimate goal was to raise critical questions and issues for academics and regulatory agencies alike, since the information generated during the last decade has both raised new questions but also clarified old ones.

A new disease was identified on the biofuel crop Jatropha curcas in 2012 in Burkina Faso that is causing serious yield losses. The disease was found to be widespread in both Sissili and Comoé Provinces. It causes characteristic leaf lesions, fruit necrosis, and cankers on young stems and branches. There was evidence of multiple infections on plants over the growing season, with regrowth evident from below old cankers, but there was little fruit production from infected branches. A detailed monitoring and assessment was undertaken of the disease progress in a severely infected field, over a 7-week period. The disease symptoms progressed from chlorosis through a necrotic phase and, in approximately 83% of replicates, stem cankers developed that resulted in dieback and lodging of branches. Colletotrichum truncatum and a member of the species complex C. gloeosporioides sensu lato were consistently isolated from fresh stem samples showing early symptoms (chlorosis). Koch's postulates were undertaken, to establish the pathogenicity of the two species. No symptoms were observed on plants inoculated with C. gloeosporioides; however, leaf and stem lesions developed after inoculation with C. truncatum, which was reisolated from the diseased tissue, confirming it as the disease-causing agent. Preliminary management practices for the disease are proposed.

The xylem-limited bacterium Xylella fastidosa causes the widely disseminated citrus variegated chlorosis disease (CVC). In Brazil, CVC has been known for more than 20 years and affects only sweet orange. Lime and mandarin have remained free of symptoms despite the high inoculum pressure. Knowing the mechanisms underlying this apparent resistance is important to devise new disease control strategies. The reaction of commercial sweet orange (‘Caipira’, ‘Natal’, ‘Pêra’, and ‘Valencia’), lime (Mexican and Persian), mandarin (‘Cleopatra’, ‘Cravo’, ‘Ponkan’, and ‘Sunki’), and the acid citrus species Rangpur to X. fastidiosa was compared in artificially inoculated seedlings, which were assessed for symptom expression, pathogen isolation, and the amount of apparently occluded xylem vessels in cross-sectioned leaf petioles. Only the sweet orange expressed typical CVC symptoms, varying from 53.8% in Valencia to 63.0% in Caipira. Average percentages of positive isolations (pi) and occluded vessels (ov) were higher in sweet orange (pi= 59.2 to 75.0; ov = 10.7 to 25.8) than mandarin (pi = 2.3 to 16.3; ov = 1.4 to 4.0), lime (pi = 0 to 5.4; ov = 0 to 2.1), or Rangpur (pi = 1,9; ov = 1.1). There were no obvious differences in xylem anatomy among all citrus varieties, suggesting that the mechanisms of resistance to CVC are not related to any physical variation in xylem structure.

Mentha longifolia is produced in and exported from Israel with annual revenue of US$16 million. In 2010, a severe epidemic of unknown etiology reduced growers' returns up to 50%. Disease symptoms included water-soaked lesions, necrosis, and web-like mycelia on plants. Two isolates (JV-1 and BS-1) from randomly selected symptomatic plants were identified as members of Rhizoctonia solani anastomosis groups 1-IB and 4HG-I, respectively. The fitness of JV-1 and BS-1 interacted with temperatures between 17 and 35°C: JV-1 grew faster and was more aggressive (P < 0.05) at lower temperatures (30°C), and the two isolates performed similarly at intermediate temperatures. Disease developed fastest at 24 to 28°C. Yield was reduced between 46 and 100%. In all, 77.5% fewer plants recovered from disease developing at 24 to 28°C than at 17 to 23 or 30 to 35°C. The relationship of disease to relative humidity (RH) fit a quadratic model (P < 0.0015, R2 = 0.98). Disease was most severe at 100% RH, decreasing by 1.3-, 1.9-, 3-, 4.5-, and 10.5-fold with the reduction of RH from 100% to 88, 76, 69, 55, or 49%, respectively. This is the first report of Rhizoctonia web blight in mint in Israel.

A syndrome has been recognized on leatherleaf fern (Rumohra adiantiformis) in Costa Rica for many years that causes widespread damage but has not been described in the literature. A full description of the syndrome, termed fern distortion syndrome (FDS), is reported here, along with evidence that FDS is a new disease and that it is associated with endophytic fluorescent pseudomonads but not with any other major groups of pathogens or pests. The main aboveground symptoms of FDS are twisting and distortions of fronds, which make the fronds unmarketable. In advanced cases of FDS, fronds are often thickened, new frond growth ceases or slows dramatically, and uneven sporulation is apparent on the underside of fronds. Symptoms of FDS belowground are reduced diameter of rhizomes and reduced overall root mass. The incidence of FDS in Costa Rica was typically over 80%, and severity typically ranged from 1.26 to 2.48 using a 0 to 3 rating scale in fields propagated vegetatively with rhizomes from fields with FDS. In contrast, in three fields planted 1.5 to 4 years previously with rhizomes derived from tissue culture, incidence and severity were markedly lower: 23 to 34% and 0.24 to 0.36, respectively. Paired sampling of symptomatic and asymptomatic plants revealed significantly greater populations of fluorescent pseudomonads inside rhizomes of symptomatic plants.

Citrus sudden death (CSD), a new disease of unknown etiology that affects sweet orange grafted on Rangpur lime, was visually monitored for 14 months in 41 groves in Brazil. Ordinary runs analysis of CSD-symptomatic trees indicated a departure from randomness of symptomatic trees status among immediately adjacent trees mainly within rows. The binomial index of dispersion (D) and the intraclass correlation (k) for various quadrat sizes suggested aggregation of CSD-symptomatic trees for almost all plots within the quadrat sizes tested. Estimated parameters of the binary form of Taylor's power law provided an overall measure of aggregation of CSD-symptomatic trees for all quadrat sizes tested. Aggregation in each plot was dependent on disease incidence. Spatial autocorrelation analysis of proximity patterns suggested that aggregation often existed among quadrats of various sizes up to three lag distances; however, significant lag positions discontinuous from main proximity patterns were rare, indicating a lack of spatial association among discrete foci. Some asymmetry was also detected for some spatial autocorrelation proximity patterns, indicating that within-row versus across-row distributions are not necessarily equivalent. These results were interpreted to mean that the cause of the disease was most likely biotic and its dissemination was common within a local area of influence that extended to approximately six trees in all directions, including adjacent trees. Where asymmetry was indicated, this area of influence was somewhat elliptical. Longer-distance patterns were not detected within the confines of the plot sizes tested. Annual rates of CSD progress based on the Gompertz model ranged from 0.37 to 2.02. Numerous similarities were found between the spatial patterns of CSD and Citrus tristeza virus (CTV) described in the literature, both in the presence of the aphid vector, Toxoptera citricida. CSD differs from CTV in that symptoms occur in sweet orange grafted on Rangpur lime. Based on the symptoms of CSD and on its spatial and temporal patterns, our hypothesis is that CSD may be caused by a similar but undescribed pathogen such as a virus and probably vectored by insects such as aphids by similar spatial processes to those affecting CTV.

To our knowledge, Ceratobasidium species have never been previously reported as a pathogen of watermelon anywhere in the United States. Because of the recent reports in Italy and confirmed incidences in major watermelon production areas in Arizona, this disease should be recognized as a potential problem in watermelon. Accepted for publication 13 November 2013. Published 25 November 2013.

Lettuce (Lactuca sativa) as annual or biennial crop is an important vegetable in China. The lettuce variety Feiqiao, which is extensively cultivated in autumn and winter, is grown for its stem and is a characteristic species bred in Yong'an City. Since October 2005, a new disease of lettuce has been observed sporadically in the fields. Initially, chlorotic symptoms, or a faded red color, were observed on the inner leaves of the infected lettuce plants. Then, the inner leaves bleached and appeared pale, while the top leaves became straight and elongated, and stopped growing. Gummosis was observed at the base of young leaves, and the whole plant became stunted and died. The disease was named lettuce chlorotic leaf rot disease. In 2008, there was a disease outbreak in Yong'an City with an incidence of approximately 30%. In 2012, total DNA was extracted from 0.1 g of leaf tissue collected from 20 symptomatic and five asymptomatic lettuce plants using the CTAB method. A PCR analysis was performed using the phytoplasma-specific primer set R16mF2/R16mR1 (1). An approximately 1.4-kb amplicon was obtained from all 20 symptomatic plants, but no corresponding DNA fragment was amplified from the five asymptomatic plants. PCR products were cloned in Escherichia coli DH5α, using the pMD18-T vector (TaKaRa, Japan), and two isolates were sequenced. The two 1,431-bp sequences were identical (GenBank Accession No. KJ668578). A BLAST analysis revealed a 99% identity between lettuce chlorotic leaf rot phytoplasma and mulberry dwarf phytoplasma, a group 16SrI phytoplasma described by Win et al. in 2012 (3). After analyzing with iPhyclassifier, the virtual RFLP pattern derived from the 16S rDNA F2n/R2 fragment was most similar to the reference pattern of the 16Sr group I, subgroup B (NC_005303), with a pattern similarity coefficient of 0.99 (2). Additionally, the leaf veins and roots with symptoms were processed for ultrastructural examinations using transmission electron microscopy. Many typical phytoplasma-like bodies were observed in the sieve elements in the leaf veins and roots, and they were spherical to oval or dumbbell shaped and 200 to 800 nm in diameter. In agreement with these findings, seven strains of phytoplasma from 16SrI-A and 16SrI-B subgroups were reported in association with lettuce plants exhibiting various types of symptoms which were not completely consistent with those observed in China (4). To our knowledge, this is the first report of a phytoplasma associated with lettuce in China. References: (1) R. E. Davis et al. Microbiol. Res. 158:229, 2003. (2) W. Wei et al. Int. J. Syst. Evol. Microbiol. 57:1855, 2006. (3) N. K. K. Win et al. J. Gen. Plant Pathol. 78:264, 2012. (4) J. Zhang et al. Phytopathology 94:842, 2004.

In Europe, chestnut blight caused by Cryphonectria parasitica (Murrill) Barr was first seen in Italy in 1938 (1). In Spain, the disease was first detected in Basque country in 1947 and later in other areas of northern Spain: Galicia, León, Navarra, and Catalonia, and in Trás-os-Montes in Portugal (2). In November 2012, in an orchard (2 ha) in Almonaster la Real (Huelva, Spain), approximately 20 cankered Castanea sativa (sweet chestnut) trees cv. Vazqueño, 40 to 50 years old, were observed. The trees were grafted 2 years before. In May and June 2013, six new disease focuses were detected near the first one. Five focuses were located in the same village and the other in Jabugo (a neighboring village). Diseased trees exhibited sunken cankers, cracked bark with mycelial fan spreads under the bark, and in some cases, orange fungal sporulation was visible on the bark. Samples were collected from two affected trees and symptom-bearing bark pieces were then placed in moist chambers at 20°C for up to 8 days to induce fungal sporulation. Cultures were made from spore masses extruding from the cankered bark and from the edge of necrotic lesions visible in the phloem of cankered bark tissue onto potato dextrose agar (PDA). Monoconidial fungal isolates were obtained from both trees. The morphological structure of two isolated fungi was identical to that described as C. parasitica (3). Species identity was confirmed by analysis of nucleotide sequences of the internal transcribed spacer (ITS) rDNA, using ITS1-ITS4 (4) as primer pairs, respectively. BLAST searches showed a high similarity between collected isolates' DNA sequences and C. parasitica sequences found on GenBank (96% coverage, 99% identity). Our isolates have been included in GenBank as KF220298 and KF220299. The pathogenicity assay of these two isolates was conducted using two cultivars of sweet chestnut (seedlings from Huelva and Granada nurseries). Isolate pathogenicity was tested on 3-year-old chestnut seedlings in a growth chamber at 25°C (day) and 20°C (night) with a 14-h photoperiod. The isolates were cultured on PDA at 25°C for 7 days. Stems were wounded at 10 cm height with a drill. Each isolate was inoculated to 25 replicates per cultivar by placing a mycelia agar plug (4 to 5 mm diameter) in the hole and wrapping the stem with Parafilm. Plants treated identically with sterile agar plugs were used as controls. Plants were then maintained at 100% relative humidity for 2 h. Both isolates induced diseases symptoms and death of seedlings of both cultivars at a mean time of 37.5 days after inoculation. No significant differences between isolates or between cultivars were detected. Twenty control plants similarly treated with sterile PDA discs did not display symptoms. C. parasitica was re-isolated from lesions, confirming Koch's postulates. Andalusia has 14,000 ha of chestnut crops with high commercial value due to their precocity. Dispersion of chestnut blight in this zone can reduce crop productivity. To our knowledge, this is the first report of C. parasitica causing chestnut blight in Andalusia (southern Spain), one of the few areas left in southwestern Europe free of chestnut blight. References: (1) A. Biraghi. Italia Agricola 7:1, 1946. (2) G. González-Varela et al. Eur. J. Plant Pathol. 131:67, 2011. (3) A. Sivanesan and P. Holliday. Cryphonectria parasitica. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 704, Set. 71. Commonwealth Mycological Institute, Kew, UK, 1981. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Amplifications. M. A. Innis et al., eds. Academic Press, San Diego, CA, 1990.

Veronica sibirica (Veronicastrum sibiricum) is an erect perennial herb, an ornamental, and a traditional Chinese medicine plant distributed mostly in northeastern, northern, and northwestern China. It has dehumidifying and detoxifying properties, and is mainly used for the treatment of cold, sore throat, mumps, rheumatism, and insect bites (4). In June 2008 through 2012, leaf spots of V. sibirica were observed in the Medicinal Herb Garden of Jilin Agricultural University (43°48′N, 125°23′E) and the medicinal plantations of Antu County (43°6′N, 128°53′E), Jilin Province. Leaf spots were amphigenous, subcircular, angular-irregular, brown, and 1 to 10 mm in diameter; they occasionally merged into a larger spot with an indefinite margin or with a pale center and dark border. Pale conidiomata were hypophyllous and scattered on the spots. The conidiophores were 100 to 400 μm high and clustered together to form synnemata 20 to 50 μm in diameter, which splayed out apically and formed loose to dense capitula. Conidiophores occasionally emerged through the stomata individually and produced conidia on the surface of the infected leaves. The conidiogenous cell terminal was geniculate-sinuous with somewhat thickened and darkened conidial scars. Conidia were solitary or catenulate, ellipsoid-ovoid or subcylindric-fusiform, hyaline and spinulose, 4.01 to 7.18 × 11.16 to 20.62 μm with obtuse to somewhat attenuated ends, and slightly thickened, darkened hila. Six isolates were obtained from necrotic tissue of leaf spots and cultured on potato dextrose agar at 25°C. After incubation for 14 days, colony surfaces were white to pinkish. The colony diameter increased by 12 mm after 21 days' incubation. Hyphae were hyaline, septate, and branched. Conidiophores grew individually or fascicularly. The symptoms and morphological characteristics were consistent with previous descriptions (1,2), and the fungus was identified as Phacellium veronicae (Pass.) (U. Braun 1990). The internal transcribed spacer (ITS) region of the nuclear rDNA was amplified using primers ITS4/ITS5 (3). The ITS was identical among all six isolates (HE995799) and 98% identical to that of P. veronicae (JQ920427, HQ690097). Pathogenicity was confirmed by spraying five 1-year-old V. sibirica seedlings with a conidial suspension (106 conidia/ml) of each isolate and five seedlings with sterile water as a control treatment. Plants were grown in the greenhouse at 20 to 25°C and were covered with plastic bags to maintain humidity on the foliage for 72 h. After 15 days, the same symptoms appeared on the leaves as described earlier for the field-grown plants; the control plants remained healthy. The same fungus was reisolated from the leaf spots of inoculated plants. Currently, the economic importance of this disease is limited, but it may become a more significant problem, as the cultivated area of V. sibirica is increasing. To our knowledge, although P. veronicae was recorded on the other species of Veronica (V. austriaca, V. chamaedrys, V. grandis, V. longifolia, V. paniculata, and V. spicata ssp. incana) in Europe (Germany, Denmark, Ireland, Romania) and V. wormskjoldii in North America (Canada) (1), this is the first report of V. sibirica leaf spots caused by P. veronicae in the world, and it is a new disease in China. References: (1) U. Braun. A monograph of Cercosporella, Ramularia and allied genera (phytopathogenic Hyphomycetes) 2, IHW-Verlag, Germany, 1998. (2) U. Braun. Nova Hedwigia 50:499, 1990. (3) D. E. L. Cooke et al. Mycol. Res. 101:667, 1997. (4) Jiangsu New Medical College. Dictionary of Chinese Materia Medica. Shanghai: Shanghai Scientific and Technical Publishers, China, 1977.

In October 2011, a new disease of dragon fruit (Hylocereus costaricensis) was discovered in a fruit market in Yuanjiang, Yunnan Province, China. Small, light brown, water-soaked spots appeared initially and then coalesced, extending to the entire fruit in 6 days. Hyaline hyphae and light brown sporangia were observed over the entire surface of the infected fruit. On potato sucrose agar (PSA) the fungus produced a white, appressed colony that covered a 9-cm diameter petri dish in less than 5 days at 25°C. The sporangiophores were hyaline, light brown to grayish, 44.71 to 143.14 (average = 85.10) μm long, and arose directly from the non-septate substrate hyphae. The sporangia were spherical, single, and terminal and yellow-brown to brown when young turning to dark brown or black at maturity. Both the sporangiophores and sporangia were covered with calcium oxalate crystals. When mounted in a drop of water, the sporangium immediately broke longitudinally into two halves, releasing the spores and exposing a large pyriform columella at the tip of the sporangiophore. The spores were mostly globose to ellipsoid, aseptate, and 5.15 (3.71 to 7.86) × 6.30 (4.08 to 9.19) μm (n = 300). Two to three slender, hyaline appendages were attached to the ends of the spores. The cardinal growth temperatures of the pathogen were 10, 30, and 40°C and it grew faster in the dark than under 12-h alternating light-dark cycles. The fungus was identified as Gilbertella persicaria (1). To confirm the identification, the internal transcribed spacer region of the nuclear rDNA of one isolate was amplified using the fungal primers ITS1 and ITS4. The nucleotide sequence (Accession No. JQ951601) showed 98% homology with G. persicaria in GenBank (HM999958). Pathogenicity tests were carried out on two species of dragon fruit, H. costaricensis and H. undatus, by placing a 6-mm diameter young mycelial PSA agar disc on the surface of an asymptomatic fruit, either unwounded or wounded with a sterile needle. As the control, a plain PSA disc was used. Each inoculated fruit was placed in a moist chamber and incubated at 25°C. Three fruits were used per treatment and the experiment was repeated twice. The fruits rotted in 2 to 3 days, and the disease was especially serious on wounded fruits and on H. costaricensis. The fungus was reisolated from infected fruits. The controls did not show any disease symptoms. Inoculation studies were also made on other fruits but rot was produced only on peach, pear, and wounded tomato. To our knowledge, this is the first record of dragon fruit rot caused by G. persicaria. The fungus had been reported in China but caused no diseases (2). In India, it caused fruit rot of pear, tomato, and peach (3). To minimize the disease, dragon fruit should be stored at low temperature and in uncovered containers. References: (1) G. L. Benny. Mycologia 83:150, 1991. (2) J. Y. Cheng and H. Y. Mei. Acta Phytotax. Sin. 10:105, 1965. (3) M. D. Mehrotra. Mycopath. Mycol. Appl. 29:151, 1966.

In September and October 2011, a new disease was observed on Buxus spp. in North Carolina and Connecticut, respectively. In North Carolina, over 10,000 containerized Buxus sempervirens (American boxwood) were affected at one location. A few weeks later, the disease was found in Connecticut on entire plantings of B. sempervirens ‘Suffruticosa’ (English boxwood) at two residential properties, and shortly thereafter on over 150,000 plants at two production nurseries. Initial foliar symptoms appeared as light to dark brown spots, often with dark borders. Spots enlarged and coalesced, often with a concentric pattern, and black streaks or cankers developed on stems. Infected leaves became brown or straw colored and dropped quickly after foliar symptoms were visible. Branch dieback and plant death were also observed in Connecticut. Cultures were isolated from symptomatic leaves and stems and identified as Cylindrocladium pseudonaviculatum Crous, Groenewald & Hill 2002 (1) (syn. Cylindrocladium buxicola Henricot 2002 [2]) on the basis of morphological characteristics. Macroconidiophores were single or in groups of up to three and comprised a stipe, stipe extension, and a penicillate arrangement of fertile branches. The stipe extension was septate, hyaline (89 to 170 × 2 to 4.5 μm), and terminated in an ellipsoidal vesicle (6 to 11 μm diameter) with a papillate or pointed apex. Conidia were cylindrical, straight, hyaline, and one septate (48 to 62 × 4 to 6 μm), occurring in slimy clusters. No microconidiophores were observed. Chlamydospores were medium to dark brown, thick walled, and smooth to rough. Microsclerotia were observed on PDA (1). A portion of β-tubulin gene sequence from two Connecticut (Genbank Accession Nos. JQ866628 and JQ866629) and two North Carolina isolates showed 100% similarity with only C. pseudonaviculatum strains. USDA-APHIS-PPQ confirmed this new United States record on October 24, 2011. Pathogenicity was confirmed by inoculating three 1-gallon container plants of B. sempervirens ‘Suffruticosa’ in North Carolina and four liners of B. sinica var. insularis × B. sempervirens ‘Green Velvet’ in Connecticut with a spore suspension of approximately 5.0 × 106 conidia (North Carolina) or 1.0 × 106 conidia (Connecticut) on the foliage of each plant; untreated control plants were sprayed with water. After incubation at ambient temperature, all inoculated plants developed foliar and stem lesions within 3 to 4 days and blighting occurred within 2 weeks; control plants remained asymptomatic. C. pseudonaviculatum was reisolated from inoculated plants. To our knowledge, this is the first report of C. pseudonaviculatum in the United States. C. pseudonaviculatum causes a serious disease of Buxus spp. in the United Kingdom and several other European countries as well as New Zealand (1). Confirmation of boxwood blight in the United States is significant because of the popularity of boxwood as a landscape plant, and because of the potential economic impact this disease may have on commercial growers; boxwood production in the United States has an annual wholesale market value of approximately $103 million (3). References: (1) P. Crous, et al. Sydowia 54:23, 2002. (2) B. Henricot and A. Culham Mycologia 94: 980, 2002. (3) USDA-NASS, Census of Horticulture, 2010.

Dead spot, also known as bentgrass dead spot or bermudagrass dead spot, is a relatively new disease of golf course putting greens and is caused by the pathogen Ophiosphaerella agrostis (1). The disease first was reported on a creeping bentgrass (Agrostis stolonifera) putting green in Maryland (2) and since has been identified on putting greens of creeping bentgrass and hybrid bermudagrass (Cynodon dactylon × C. transvaalensis) in the eastern and southern United States (3,4). In June 2004, disease symptoms resembling dead spot were observed on a golf course in southern Ontario. Small (≤3 cm) spots first appeared approximately 14 months after establishment of the sand-based, ‘L-93’ creeping bentgrass putting greens. The disease became more severe during the summer months and patches increased in size to as much as 5 to 8 cm in diameter. Dead spot infection centers remained visible throughout the winter months and the disease again became active during the spring of 2005. Bentgrass tissues growing adjacent to the periphery of active infection centers were orange-red to reddish-brown. Although dark brown ectotrophic hyphae were observed on bentgrass stolons, none were found on the roots. Few new infection centers occurred in 2005 and pseudothecia embedded within necrotic tissue only were observed in small numbers. No mature ascospores were observed when samples were collected during September 2005. A single fungal morphotype consistently was isolated from leaves and stolons with a rose-quartz color when grown for several days on potato dextrose agar. To demonstrate pathogenicity, ‘L-93’ creeping bentgrass seedlings were grown for 28 days in 10-cm-diameter pots containing an autoclaved greens-mix with a mechanical analysis of 94% sand, 5% silt, and 1% clay. Inoculum was prepared by placing mycelia from a hyphal-tipped isolate on an autoclaved mix of seed of tall fescue (Festuca arundinacea) and wheat (Triticum aestivum) bran (50% [vol/vol]), and grown at 24°C for 14 days. The inoculum (5 g) was embedded a few milliliters into the sand in the center of each pot (n = 5), and uninfested inoculum served as the untreated control. Pots were placed in enclosed plastic containers and incubated at room temperature (13 to 26°C) under natural light (replication 1) or under 14 h of light per day from fluorescent lights (replication 2). After 7 days, tissue along the periphery of each inoculation point became covered in a pink mycelium, and newly infected leaves appeared tan or brownish-red. Most plants were dead after 22 to 28 days of incubation. Reisolation of the pathogen from necrotic leaves produced fungal colonies similar in color, morphology, and growth rate to the original isolates. Few pseudothecia developed on infected tissue but were present in large numbers on infested tall fescue seed. Bitunicate asci containing spirally twisted filiform ascospores were observed. Light brown ascospores (n = 50) were 7 to 15 septate and measured 1.9 to 3.6 μm × 60.7 to 147.9 μm. On the basis of field symptoms, morphological characteristics, and pathogenicity tests, the pathogen was identified as O. agrostis. To our knowledge, this is the first report of dead spot on creeping bentgrass in Canada and of O. agrostis outside the United States. References: (1) M. P. S. Câmara et al. Mycologia 92:317, 2000. (2) P. H. Dernoeden et al. Plant Dis. 83:397, 1999. (3) J. E. Kaminski and P. H. Dernoeden. Plant Dis. 86:1253, 2002. (4) J. P. Krausz et al. Plant Dis. 85:1286, 2001.

A new disease was found in September 2001 on greenhouse-produced onion transplants of cv. Colorado 6 grown in a field in Larimer County in northern Colorado. Symptoms included straw-colored, dry, tan, spindle- or diamond-shaped lesions on the leaves and scapes of onion plants. Infected plants were scattered (less than 5% incidence) throughout the outer perimeter of the sprinkler-irrigated field. Iris yellow spot virus (IYSV) in two collections each with 4 to 6 symptomatic onion plants was confirmed with western blot assays by James Moyer of North Carolina State University. Western blot showed a faint band from protein extracts of infected Nicotiana benethimiana. Western blot assay is the most definitive method of identification. IYSV can be mechanically transmitted to N. benethimiana, but it cannot be recovered and transmitted back to onion, and it is difficult to detect in infected onion plants. IYSV is a tospovirus that is transmitted by various species of thrips, including onion thrips and western flower thrips (1). The host range for this disease includes onion, leek, and iris. IYSV has been reported previously on onion in Israel, Brazil, and Idaho (2). There are no reports that this disease affects bulb quality or marketability; however, heavy losses of onion bulb production are reported (1). University and industry personnel in other onion-growing areas of the country are encouraged to monitor onion and other host fields for evidence and distribution of IYSV. References: (1) A. Kritzman et al. Plant Dis. 85:838, 2001. (2) L. Pozzer et al. Plant Dis. 83:345, 1999.

In 1992 symptoms consisting of twig dieback, canker-like deformities, and often, mortality of all sizes of container-grown flowering dogwood trees (Cornus florida L.) was frequently observed in northern Florida where nursery production of dogwood is concentrated. Twigs, branches, growing points, and portions of main trunks up to 3 cm in diameter were killed. On affected portions, leaves drooped downward but did not wilt severely; they later became silvery, gray-green and eventually died but did not drop. Affected trees produced flower buds, but the flower buds did not open. Many trees died and others were destroyed because of unsightly dead limbs and deformed trunks. The inciting pathogen was not satisfactorily determined. After 1994, disease incidence subsided, but in 1999, it reappeared and caused serious economic damage. In 1999, we followed the disease from propagation through several stages of nursery production, including growth in large containers. A Colletotrichum species was consistently isolated from acervuli produced in abundance near the soil line on diseased, rooted cuttings and small plants. The same fungus was consistently isolated from acervuli produced on diseased leaves and twigs of larger plants and small trees. Conidia of the isolated pathogen were used to inoculate small dogwood trees kept at 100% RH for 2 days then grown in a greenhouse. Within 23 weeks, a slowly developing leaf spot was produced on inoculated plants. After 3 months, numerous acervuli were produced on inoculated leaves and on adjacent small twigs from which the same pathogen was consistently reisolated. The symptoms and pathogen were not consistent with descriptions of anthracnose incited by Discula destructiva. On potato-dextrose agar (PDA), spore masses were bright red-orange on lawn plates inoculated with large numbers of conidia. Conidiomata did not produce setae in culture nor did acervuli on diseased plant material. On PDA, mycelial growth was tufted and pale-gray. The reverse side of colonies was buff to cream-colored or pale-gray to tan but never dark. With age, a pale pink or orange-pink pigment often formed within the agar media (1,3). When produced on PDA, most conidia were elliptical and elongated with abruptly tapering ends. An average of 18% had both ends slightly rounded; none had only one end abruptly tapered or rounded. Conidia measured 15.3 × 4.78 μm; the length/width ratio was 3.20 (1,3). The teleomorph was not found on diseased plant material or in culture. Analysis of DNA by polymerase chain reaction (PCR) using the CaInt2-ITS4 and CgInt-ITS4 primer pairs (1,2) and by comparison of PCR products with those produced by C. acutatum pathotypes isolated from leatherleaf fern, lime, post-bloom fruit drop-affected Navel orange fruit, and strawberry fruit, and with isolates of C. gleosporiodes from citrus, Camellia, Nandina, holly, and strawberry indicated that the fungus was C. acutatum. The amplified PCR product (approximately 490 bp) obtained from all dogwood isolates using primers CaInt2 and ITS4 was consistent with the size of product expected from C. acutatum. No products were produced with the CgInt-ITS4 primer pair. Based on the morphology of conidia, growth in culture and PCR results, the pathogen was identified as C. acutatum and represents the first report of this pathogen on flowering dogwood. References: (1) J. E. Adaskaveg and R. J. Hartin. Phytopathology 87:979, 1997. (2) A. E. Brown et al. Phytopathology 86:523, 1996. (3) B. C. Sutton. Pages 1–27 in: Colletotrichum: Biology, pathology and control. Brit. Soc. For Plant Pathol., CAB International, 1992.