scholarly journals First Report of Choke Disease Caused by Epichloë typhina on Orchardgrass (Dactylis glomerata) in China

Plant Disease ◽  
2009 ◽  
Vol 93 (6) ◽  
pp. 673-673 ◽  
Author(s):  
C. J. Li ◽  
Z. F. Wang ◽  
N. Chen ◽  
Z. B. Nan
Keyword(s):  
Dactylis Glomerata ◽  
The United States ◽  
Leaf Sheath ◽  
Climatic Conditions ◽  
Disease Spread ◽  
Willamette Valley ◽  
First Report ◽  
Epichloë Typhina ◽  
Pure Cultures ◽  
Choke Disease

Orchardgrass or cocksfoot (Dactylis glomerata L.) has been widely cultivated as a forage crop in many provinces of China (1). It is also a native perennial forage grass, which grows at the edge of forests, shrubs, and mountainous grasslands in Xinjiang and Sichuan (2). In September of 2007, signs of choke disease on orchardgrass were observed in a native grassland under birch woodland near Altai City, Xinjiang, China. Stromata, which formed on culms of diseased grass, enclosing the inflorescence and leaf sheath, were 4.5 to 5.5 mm long, smooth or wrinkled, white and later becoming yellowish or yellow, tuberculate, dry, and covered with perithecia. Inflorescences surrounded by fungal stromata were choked and failed to mature, thus restricting seed production. Pure cultures were obtained by directly scraping stromata from the surface and incubating it on antibiotic potato dextrose agar (PDA). The colonies were cottony, white on the upper surface, and white to yellow on the reverse. The growth rate was 13 to 21 mm per week at 25°C on PDA. Conidia were hyaline, lunate to reniform, and measured 4.1 ± 0.5 × 2.2 ± 0.5 μm. They accumulated in small globose heads at the tips of conidiogenous cells and were produced singly on conidiophores of 13 to 33 μm long and 2.7 to 4.1 μm wide at the base. Internal transcribed spacer (ITS) sequence by BLAST search had 99% similarity with an Epichloë typhina isolate of orchardgrass in Spain (GenBank Accession No. AM262420.1). Cultural characteristics, microscopic examination, and phylogenetic analysis showed that this choke disease on D. glomerata was caused by the fungus E. typhina (Pers.) Tul. & C. Tul. as described by White (4). To our knowledge, this is the first report of E. typhina causing choke disease on orchardgrass in China. The pathogen has been identified in France, England, Germany, Sweden, Switzerland, and the United States (3,4) with the same symptoms as those reported here. In 1997, choke disease was found in 70% of the fields in the Willamette Valley of Oregon, with disease incidences ranging from 0.05 to 28%. It was predicted to increase and spread under the prevailing climatic conditions (3). This new disease report is to provide observational and diagnostic information to help with recognition and prevention of disease spread in orchardgrass cultivation regions of China. References: (1) X. R. Chao et al. Shandong Agric. Sci. 1:7, 2005. (2) S. X. Jia, ed. China Forage Plant Flora. China Agriculture Press, Beijing, 1987. (3) W. F. Pfender and S. C. Alderman. Plant Dis. 83:754, 1999. (4) J. W. White. Mycologia 85:444, 1993.

scholarly journals Geographical Distribution and Incidence of Orchardgrass Choke, Caused by Epichloë typhina, in Oregon

Plant Disease ◽  
1999 ◽  
Vol 83 (8) ◽  
pp. 754-758 ◽  
Author(s):  
W. F. Pfender ◽  
S. C. Alderman
Keyword(s):  
Disease Incidence ◽  
Dactylis Glomerata ◽  
Willamette Valley ◽  
Cultural Conditions ◽  
The World ◽  
Epichloë Typhina ◽  
Severe Constraint ◽  
Production Area ◽  
One Year ◽  
Choke Disease

A 1998 survey was conducted in the Willamette Valley of Oregon, the major U.S. production area for orchardgrass seed, to determine the extent and severity of choke disease in Dactylis glomerata. This disease is a severe constraint to orchardgrass seed production in other parts of the world, but was unknown in Oregon prior to 1997. Thirty-seven fields, representing 27 cultivars and the geographical extent of production in the Willamette Valley, were selected from a list of fields registered for certification. Choke was found in 26 (70%) of the fields, and disease incidence ranged from <0.05 to 28% tillers affected. Five of the 37 fields had only trace levels of the disease, but four of the fields, representing three counties, had incidences >10%. In a survey of 16 fields located within 3.5 km of the 1997 discovery, choke was found in 14 fields, of which three had incidences >20%. Increase in disease incidence between 1997 and 1998 ranged from 2.1- to 3.3-fold in the three fields where disease increase was measured. One year after its presence was confirmed in Oregon, choke disease of orchardgrass is well-established throughout the orchardgrass seed producing region at damaging levels and is apparently able to increase and spread under the prevailing climatic and cultural conditions.

First Report of Dicyma pulvinata on Epichloë typhina and Its Potential for Control of E. typhina

2010 ◽  
Vol 11 (1) ◽  
pp. 25 ◽  
Author(s):  
Stephen C. Alderman ◽  
Sujaya Rao ◽  
Ruth Martin
Keyword(s):  
Seed Production ◽  
Biocontrol Agent ◽  
Field Conditions ◽  
High Humidity ◽  
Willamette Valley ◽  
First Report ◽  
Epichloë Typhina ◽  
Low Humidity ◽  
First Time ◽  
Choke Disease

The hyperparasite Dicyma pulvinata is reported for the first time on Epichloë typhina, which causes choke disease in orchardgrass seed production fields in the Willamette Valley, OR. In an orchardgrass field near Corvallis, OR, D. pulvinata was found on 7% of E. typhina stromata. Infected stromata had fewer perithecia and appeared shrunken, desiccated, and pale gray to grayish-white, in contrast to the orange colored noninfected stromata with mature perithecia. In greenhouse inoculations, D. pulvinata significantly (P < 0.05) reduced perithecial formation on E. typhina. However, under field conditions, a significant (P < 0.05) reduction in perithecial development occurred in one trial initiated in mid-May, but not in a second trial initiated in early June, although D. pulvinata sporulated on 92% of the inoculated stromata from each trial within 72 h after their incubation in moist chambers. Under field conditions, D. pulvinata may have potential as a biocontrol agent of E. typhina if applied when stromata start to emerge during mid late April to early May when rain and high humidity conditions are typical. However, development of D. pulvinata would likely be limited by low humidity conditions that often occur during mid- to late June in the Willamette Valley. There are currently no effective chemical or cultural controls for choke in orchardgrass. Accepted for publication 3 November 2009. Published 16 February 2010.

scholarly journals First Report of Seedling Blight Caused by Sclerotium rolfsii on Wheat in Oklahoma

Plant Disease ◽  
2006 ◽  
Vol 90 (5) ◽  
pp. 686-686 ◽  
Author(s):  
V. Choppakatla ◽  
R. M. Hunger ◽  
H. A. Melouk
Keyword(s):  
Filter Paper ◽  
Sclerotium Rolfsii ◽  
Significant Risk ◽  
Triticum Aestivum L ◽  
The United States ◽  
Damping Off ◽  
Wheat Seedlings ◽  
First Report ◽  
Significant Difference ◽  
Pure Cultures

Wheat (Triticum aestivum L.) is an important crop in Oklahoma and throughout the Central Plains of the United States. The soilborne fungus, Sclerotium rolfsii, is a major pathogen on peanut (Arachis hypogaea L.) but is not known to cause major damage on wheat. During September of 1998, damping-off and rotting of young wheat seedlings were observed in breeder plots in Payne County, OK. The occurrence of symptoms was sporadic with an estimated stand reduction of 10 to 15%. Symptomatic plants were collected from the field and brought to the laboratory. Sclerotia-like bodies from the symptomatic plants were surface disinfested in aqueous 1% NaOCl for 2 min and allowed to germinate at 25 ± 2°C on sterile filter paper moistened with a 1% aqueous solution of methanol. Aerial mycelia from germinating sclerotia were transferred to potato dextrose agar amended with 100 ppm of streptomycin (SPDA) to obtain pure cultures. Pure cultures had coarse, white mycelium distinctive of S. rolfsii and produced very small (0.05 to 0.1 mm), abundant, round, brown sclerotia on the surface of the medium after 15 days of incubation. Pathogenicity was tested on three hard red winter wheat cultivars commonly grown in Oklahoma (Jagger, 2137, and 2174). Four plants of each cultivar were inoculated at the two-leaf stage (Feekes' scale stage 1) by placing a 0.5-cm agar disk removed from a 3-day-old culture onto a 1-cm diameter filter paper that was then pressed to the base of the shoot. Noninoculated plants were used as a control. After inoculation, pots were covered with polyethylene sheets to maintain 95 to 100% relative humidity and incubated at 25 ± 2°C in the greenhouse. Lesions were initially superficial, yellowish, and water soaked. Lesions expanded and resulted in damping-off of seedlings. Noninoculated plants were free of disease and remained healthy. No significant difference (P ≤ 0.05) in disease severity was observed among the cultivars. To fulfill Koch's postulates, the fungus was reisolated onto SPDA where it had the same characteristics as the initial culture. To our knowledge, this is the first report of S. rolfsii on wheat in Oklahoma. Even though S. rolfsii is not expected to pose a significant risk to wheat production, infection of wheat may enhance survival of S. rolfsii and facilitate infection and losses in a following peanut crop. This is especially important in certain areas of Oklahoma where a wheat-peanut rotation is occasionally practiced.

scholarly journals First Report of Leaf Spot Caused by Phyllosticta yuccae on Yucca filamentosa in Brazil

Plant Disease ◽  
2013 ◽  
Vol 97 (9) ◽  
pp. 1257-1257 ◽  
Author(s):  
A. D. A. Silva ◽  
D. B. Pinho ◽  
B. T. Hora Junior ◽  
O. L. Pereira
Keyword(s):  
Leaf Spot ◽  
Its Region ◽  
The United States ◽  
Leaf Spot Disease ◽  
Infected Leaf ◽  
Single Spore ◽  
First Report ◽  
Leaf Spots ◽  
Slime Layer ◽  
Pure Cultures

Yucca filamentosa L. (Agavaceae), commonly known as Adam's needle, is known in Brazil as “agulha-de-adão.” It is an ornamental garden plant with medicinal properties (4). In 2010, 100% of Y. filamentosa seedlings and plants were observed with a severe leaf spot disease in two ornamental nurseries located in the municipality of Viçosa, Minas Gerais, Brazil. Initially, lesions were dark brown, elliptical, and scattered, and later became grayish at the center with a reddish brown margin, irregular and coalescent. Infected leaf samples were deposited in the herbarium at the Universidade Federal de Viçosa (Accession Nos. VIC32054 and VIC32055). A fungus was isolated from the leaf spots and single-spore pure cultures were obtained on potato dextrose agar (PDA). The sporulating single-spore cultures were deposited at the Coleção de Culturas de Fungos Fitopatogênicos “Prof. Maria Menezes” (CMM 1843 and CMM 1844). On the leaf, the fungus produced pycnidial conidiomata that were scattered or gregarious, usually epiphyllous, immersed, dark brown, unilocular, subglobose, and 95 to 158 × 108 to 175 μm, with a minute, subcircular ostiole. Conidiogenous cells were blastic, hyaline, conoidal, or short cylindrical. Conidia were aseptate, hyaline, smooth walled, coarsely granular, broadly ellipsoidal to subglobose or obovate, usually broadly rounded at both ends, occasionally truncate at the base or indented slightly at the apex, and 7.5 to 13.5 × 6 to 10 μm. Conidia were also surrounded by a slime layer, usually with a hyaline, flexuous, narrowly conoidal or cylindrical, mucilaginous apical appendage that was 10 to 16 μm long. Spermatia were hyaline, dumbbell shaped to cylindrical, both ends bluntly rounded, and 3 to 5 × 1 to 1.5 μm. These characteristics matched well with the description of Phyllosticta yuccae Bissett (1). To confirm this identification, DNA was extracted using a Wizard Genomic DNA Purification Kit and amplified using primers ITS1 and ITS4 (2) for the ITS region (GenBank Accession Nos. JX227945 and JX227946) and EF1-F and EF2-R (3) for the TEF-1α (JX227947 and JX227948). The sequencing was performed by Macrogen, South Korea. The ITS sequence matched sequence No. JN692541, P. yuccae, with 100% identity. To confirm Koch's postulates, four leaves of Y. filamentosa (five plants) were inoculated with 6-mm-diameter plugs from a 7-day-old culture growing on PDA. The leaves were covered with plastic sack and plants were maintained at 25°C. In a similar manner, fungus-free PDA plugs were placed on five control plants. Symptoms were consistently similar to those initially observed in the nurseries and all plants developed leaf spots by 15 days after inoculation. P. yuccae was successfully reisolated from the symptomatic tissue and control plants remained symptomless. P. yuccae has been previously reported in Canada, the Dominican Republic, Guatemala, Iran, and the United States of America. To our knowledge, this is the first report of P. yuccae causing disease in Y. filamentosa in Brazil and it may become a serious problem for the nurseries, due to the severity of the disease and the lack of chemical products to control this pathogen. References: (1) J. Bissett. Can. J. Bot. 64:1720, 1986. (2) M. A. Innis et al. PCR Protocols: A guide to methods and applications. Academic Press, 1990. (3) Jacobs et al. Mycol. Res. 108:411, 2004. (4) H. Lorenzi and H. M. Souza. Plantas Ornamentais no Brasil. Instituto Plantarum, 2001.

Ascosporic Fertilization of Epichloë typhina in Dactylis glomerata Seed Production Fields in Oregon and Implications for Choke Management

2008 ◽  
Vol 9 (1) ◽  
pp. 47 ◽  
Author(s):  
S. C. Alderman ◽  
S. Rao
Keyword(s):  
Seed Production ◽  
Dactylis Glomerata ◽  
Causal Agent ◽  
First Report ◽  
Epichloë Typhina

Epichloë typhina, causal agent of choke, is a fungus that systemically infects the crown and foliage of Dactylis glomerata(orchardgrass). The process of infection of orchardgrass by E. typhina has not been fully established, but ascospores are believed to be responsible for new plant infections. The objective of this study was to determine if ascospores could serve as spermatia and fertilize stromata of E. typhina. To our knowledge, this is the first report of ascosporic fertilization in the genus Epichloë. Accepted for publication 28 January 2008. Published 21 April 2008.

scholarly journals First Report of Cocksfoot mottle virus Infecting Dactylis glomerata in Oregon and the United States

Plant Disease ◽  
2016 ◽  
Vol 100 (5) ◽  
pp. 1030 ◽  
Author(s):  
S. C. Alderman ◽  
R. C. Martin ◽  
B. S. Gilmore ◽  
R. R. Martin ◽  
G. D. Hoffman ◽  
...  
Keyword(s):  
United States ◽  
Dactylis Glomerata ◽  
The United States ◽  
Mottle Virus ◽  
First Report ◽  
Cocksfoot Mottle Virus

scholarly journals First Report of Five Sooty Blotch and Flyspeck Fungi on Prunus americana in the United States

Plant Disease ◽  
2007 ◽  
Vol 91 (12) ◽  
pp. 1685-1685 ◽  
Author(s):  
J. Latinović ◽  
J. C. Batzer ◽  
K. B. Duttweiler ◽  
M. L. Gleason ◽  
G. Sun
Keyword(s):  
United States ◽  
The United States ◽  
Apple Fruit ◽  
Economic Losses ◽  
Research Station ◽  
First Report ◽  
Sooty Blotch ◽  
Sooty Blotch And Flyspeck ◽  
Pcr Products ◽  
Pure Cultures

The sooty blotch and flyspeck (SBFS) complex includes more than 30 fungi that blemish the cuticle of apple fruit, causing economic losses in humid regions worldwide (1). In August 2005, we sampled SBFS-infested wild plum (Prunus americana) fruit growing in hedgerows in Iowa. Colonies were categorized according to mycelial type (1), and isolates were made from representative colonies onto acidified water agar (AWA). Plum skins with SBFS signs were excised, pressed, and photographed. DNA was obtained from purified isolates and also from mycelium and fruiting bodies scraped directly from plum fruit skins. Extracted DNA was amplified using primer pair ITS1-F/Myc1-R (ACTCGTCGAAGGAGCTACG) and PCR products were sequenced using primer pair ITS-1F/ITS4. Six sequences were obtained from pure cultures and seven from colonies on plum fruit skin. BLAST analysis of the 470-bp sequences showed 100% homology to five known species in the SBFS complex: Zygophiala cryptogama, Zygophiala wisconsinensis, Pseudocercosporella sp. RH1, and Stomiopeltis spp. RS1 and RS2 (GenBank Accession Nos. AY598854, AY598853, AY5988645, AY598882, and AY598883, respectively). Observations of colony and fruiting structure morphology from cultures on potato dextrose agar (PDA) and colonies on plums confirmed species identity. A modified version of Koch's postulates was conducted to verify that these fungi caused the signs observed on plum and could also infest apple fruit. In June 2006, 1-month-old cultures on PDA were pulverized in a blender with sterile distilled water, passed through four layers of sterile cheesecloth, and transferred to sterile jars. Each isolate was inoculated onto 20 fruit on plum trees (P. americana) on the Iowa State University (ISU) campus and 20 fruit on cv. Golden Delicious apple trees at the ISU Research Station, Gilbert, IA. Each fruit was disinfested with 70% ethanol, air dried, swabbed with inoculum, and covered with a Fuji bag. At harvest, fungal colonies on fruit were reisolated onto AWA. DNA was extracted from pure cultures; when isolations on agar were unsuccessful, DNA was extracted directly from colonies on fruit. PCR was conducted using ITS1-F/Myc1-R, and PCR products were sequenced using ITS1-F/ITS4. All five species were reisolated and sequenced from apple. Pseudocercosporella sp. RH1 and Stomiopeltis sp. RS1 were sequenced from inoculated plums. Although flyspeck, presumably caused by Schizothyrium pomi, was reported on Japanese plum (P. salicina) in Japan (2) and black cherry (P. serotina) in the United States (3), to our knowledge this is the first report of SBFS fungi on plum in the United States and the first confirmation that fungi from plum can produce SBFS signs on apple fruit. Wild plum may therefore act as a reservoir host, providing inoculum for SBFS infestations on apple. References: (1) J. Batzer et al. Mycologia 97:1268, 2005. (2) H. Nasu and H. Kunoh. Plant Dis. 71:361, 1987. (3) T. B. Sutton. Plant Dis. 72:801, 1988.

scholarly journals First Report of a Bacterial Disease on Creeping Bentgrass (Agrostis stolonifera) Caused by Acidovorax spp. in the United States

Plant Disease ◽  
2010 ◽  
Vol 94 (7) ◽  
pp. 922-922 ◽  
Author(s):  
P. R. Giordano ◽  
J. M. Vargas ◽  
A. R. Detweiler ◽  
N. M. Dykema ◽  
L. Yan
Keyword(s):  
United States ◽  
16S Rdna ◽  
Creeping Bentgrass ◽  
The United States ◽  
Agrostis Stolonifera ◽  
Bacterial Disease ◽  
16S Rdna Sequencing ◽  
First Report ◽  
Rdna Sequencing ◽  
Pure Cultures

In June of 2009, a golf course putting green sample of creeping bentgrass (Agrostis stolonifera L.) cv. Penn G-2 from a golf club in North Carolina was submitted to the Michigan State University Turfgrass Disease Diagnostic Laboratory for diagnosis. The sample exhibited symptoms of general wilt, decline, and characteristic necrosis from the leaf tips down. Fungal pathogens were ruled out when no phytopathogenic fungal structures were observed with microscopic examination of infected tissue. Symptoms appeared similar to those of annual bluegrass affected by bacterial wilt caused by Xanthomonas translucens pv. poae. Bacterial streaming was present in all of the cut infected tissue of the Penn G-2 bentgrass sample when observed with a microscope. To isolate the causal agent, cut leaf tissue (1- to 3-mm tips) exhibiting bacterial streaming was surface disinfected for 1 min in 10% sodium hypochlorite solution and rinsed for 1 min with sterile distilled water. Leaf blades were placed into Eppendorf microtubes with 20 μl of sterile phosphate-buffered saline (PBS) solution (pH 7) and macerated with a sterile scalpel. Serial dilutions up to 1 × 10–4 were performed in sterile PBS; 10 μl of each suspension was plated onto nutrient agar (NA) (Becton Dickinson, Sparks, MD) and incubated at room temperature for 5 days. Pure cultures of three commonly observed single bacterial colonies growing on plates from serial dilutions were made on NA medium. These pure cultures were grown for 5 days and used to inoculate three replicates of 5-week-old Penn G-2 plants that had uniformly filled in 8.5-cm-diameter pots grown under greenhouse conditions. Uninfected Penn G-2 creeping bentgrass plants were inoculated with 1 ml of 1.3 × 109 CFU/ml of bacterial suspension by adding drops of the suspension to blades of sterile scissors used to cut the healthy plants. Of the three different bacterial cultures selected to inoculate healthy plants, only one resulted in slight browning of leaf tips just 2 days after inoculation. The symptoms progressed, and by 5 days after inoculation, browning, twisting and leaf dieback to the sheath were observed. When leaf tips of the inoculated plants were cut, bacterial streaming was observed. Isolation of the bacterium from inoculated Penn G-2 plants was performed to fulfill Koch's postulates. Once isolated, a single bacterial colony was identified by 16S rDNA sequencing (Microcheck Inc. Northfield, VT). 16S rDNA sequencing results indicated that the causal agent of bacterial infection was a member of the Acidovorax genus, with a 100% sequence match to Acidovorax avenae subsp. avenae (2). The same nonflorescent, aerobic, gram-negative bacterium has been consistently isolated from inoculated plants exhibiting symptoms thus far. A member of the Acidovorax genus has also been identified as a pathogen of creeping bentgrass in Japan (1). To our knowledge, this is the first report of a bacterial disease affecting creeping bentgrass caused by Acidovorax spp. in the United States. References: (1) N. Furuya et al. J. Fac. Agric. Kyushu Univ. 54:13. 2009. (2) N. Schaad et al. Syst. Appl. Microbiol. 31:434. 2008.

scholarly journals First Report of Canola Powdery Mildew Caused by Erysiphe polygoni in Argentina

Plant Disease ◽  
2004 ◽  
Vol 88 (10) ◽  
pp. 1163-1163 ◽  
Author(s):  
S. Gaetán ◽  
M. Madia
Keyword(s):  
Powdery Mildew ◽  
Buenos Aires ◽  
Disease Incidence ◽  
Fungal Growth ◽  
The United States ◽  
Climatic Conditions ◽  
Width Ratio ◽  
Infected Leaf ◽  
First Report ◽  
Erysiphe Polygoni

Canola (Brassica napus) is a developing oleaginous crop grown commercially in the Buenos Aires and Santa Fe provinces of Argentina. During the autumn of 2003, typical signs of powdery mildew were observed on canola plants in experimental field plots in Buenos Aires. Average disease incidence was 42% on 3- to 6-month-old canola cultivars developed in the following countries: Argentina (Eclipse, Impulse Master, Mistral, and Nolza); Australia (Oscar and Rainbow); Canada (Sentry); France (Cadillac, Camberra, and Capitol); and Sweden (Maskot, Sponsor, and Wildcat). The range of incidence on these cultivars was 35 to 93%. Other cultivars exhibited an apparent high level of resistance or escaped disease. These included: Charlton (Argentina); 46CO3, Dunkeld, Insignia, Mystic, Monty, Outback, Rivette, and Surpass 400 (Australia), and Caviar (France). Climatic conditions in Buenos Aires, especially rainfall, from March to May 2003 were apparently favorable for powdery mildew development. On susceptible cultivars, fungal growth was observed on leaves, stems, and pods that resulted in premature senescence of the tissues. The mycelium, with multilobed hausthoria, was white to gray, dense or fine, and in patches or covering the entire adaxial leaf surfaces. Appressoria were lobed and conidiophores were straight. Foot cells were cylindrical, straight, measured 35 to 42 × 7 to 10 μm, and were followed by two cells. Conidia were produced singly, cylindrical to ovoid, and measured 36 to 40 × 18 to 20 μm. The conidial length-to-width ratio was 2.0. No fibrosin bodies were observed in the conidia and conidia germinated at the ends. Cleistothecia were not observed. On the basis of mycelial, conidial, and hausthoria characteristics observed on six leaves for each affected cultivar, the fungus was identified as Erysiphe polygoni DC (1). Pathogenicity was confirmed on 5-week-old canola plants of cvs. Eclipse, Impulse, Master, Mistral, and Maskot by gently pressing (1 min) one adaxial infected leaf with abundant sporulation onto one adaxial healthy leaf. The experiment, which included five inoculated plants and three noninoculated control plants for each cultivar, was conducted in a greenhouse at 22 to 24°C and maintained at 75% relative humidity with no supplemental light. Inoculated and control plants were covered with polyethylene bags for 48 h after inoculation. Powdery mildew developed on all inoculated plants of all cultivars after 12 to14 days. The control plants did not develop disease. The experiment was repeated with similar results. E. polygoni has a worldwide distribution (2); however, the results suggest that this fungus may be a threat to the main cultivars being grown in Argentina (Eclipse, Impulse, Master, Mistral, and Nolza), since high levels of disease incidence, as much as 70%, were observed. Under propitious environments, this pathogen could cause severe yield losses in commercially grown canola in Argentina. To our knowledge, this is the first report of canola powdery mildew caused by E. polygoni in Argentina. References: (1) H. J. Boesewinkel. Rev. Mycol. Tome 41:493, 1977. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St.Paul, MN, 1989.

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