scholarly journals First Report of Occurrence of Sclerotinia Blight on Petunia in Louisiana

Plant Disease ◽  
2001 ◽  
Vol 85 (1) ◽  
pp. 95-95
Author(s):  
G. E. Holcomb
Keyword(s):  
Petunia Hybrida ◽  
Baton Rouge ◽  
The United States ◽  
Tidal Wave ◽  
Sclerotinia Blight ◽  
Pathogenicity Tests ◽  
Wave Rose ◽  
Stem Lesions ◽  
Prostrate Growth ◽  
Branch Death

Petunia × hybrida Wave series cultivars were observed with symptoms of tan to brown stem lesions, wilt, and branch death in a demonstration/trial planting at Burden Research Center in Baton Rouge, LA, during January and February 2000. Disease signs included the presence of white, cottony mycelia on infected stems and the presence of black sclerotia. Seventeen of 131 plants were infected on 20 February and included individuals of cvs. Wave Purple, Wave Rose, Wave Misty Lilac, Wave Pink, Tidal Wave Hot Pink, and Tidal Wave Cherry. Isolations were made by placing diseased stem sections on acidified potato-dextrose agar. A fungus that produced white mycelia and black sclerotia was consistently isolated from infected stems and identified as Sclerotinia sclerotiorum. Pathogenicity tests were done by pipetting 1 to 2 ml of blended mycelia and sclerotia (one plate culture blended in 100 ml distilled water) at the base of flowering-age Wave series plants. Plants were held for 3 days in a dew chamber maintained at 22°C and then moved to a greenhouse held at 25°C. Wilt and branch death developed on inoculated plants after 5 days and S. sclerotiorum was reisolated. Uninoculated plants remained healthy. Wave series cultivars have a prostrate growth habit that is conducive to disease development. No plants in the trial planting were killed and infected plants had recovered by 1 May and had uniformly covered the plant bed. Sclerotinia blight was previously reported on Petunia × hybrida from Bermuda (2) and Florida (1). References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN. (2) J. M. Waterston. Dept. Agric. Bermuda Rep., 1947.

scholarly journals First Report of Web Blight on Verbena Caused by Rhizoctonia solani

Plant Disease ◽  
2000 ◽  
Vol 84 (4) ◽  
pp. 492-492 ◽  
Author(s):  
G. E. Holcomb ◽  
D. E. Carling
Keyword(s):  
Rhizoctonia Solani ◽  
Fungal Pathogen ◽  
Baton Rouge ◽  
Anastomosis Group ◽  
First Report ◽  
Foliage Blight ◽  
Pathogenicity Tests ◽  
Stem Lesions ◽  
Web Blight ◽  
Branch Death

Web blight was observed on verbena (Verbena × hybrida) during July 1999 in a cultivar trial planting at Burden Research Plantation in Baton Rouge, LA. Foliage blight, stem lesions, and branch death were common symptoms on 12 of 24 cultivars in the trial. Plant death occurred in cvs. Babylon Florena (one of four plants), Purple Princess (two of four plants), and Taylortown Red (two of four plants). Isolations from infected leaves and stems on acidified water agar consistently yielded a fungus with the mycelial and cultural characteristics of Rhizoctonia solani. Pathogenicity tests were carried out by placing 5-day-old fungal mycelial plugs, grown on acidified potato dextrose agar, at the base of healthy verbena stems and holding plants in a dew chamber at 26°C. After 3 days, foliage blight and stem lesions appeared on inoculated plants, and plants were moved to a greenhouse where temperatures ranged from 23 to 32°C. Seven of nine inoculated plants died after 7 days; noninoculated plants remained healthy. The fungal pathogen was reisolated from all inoculated plants. The fungus was identified as R. solani anastomosis group (AG)-1 IB based on multinucleate condition, type of sclerotia produced, and ability to anastomose with R. solani tester isolates of AG-1 IB. This is the first report of web blight on verbena.

scholarly journals First Report of Sclerotinia minor Infecting Ipomoea hederacea and I. coccinea in Texas

Plant Disease ◽  
2008 ◽  
Vol 92 (3) ◽  
pp. 482-482 ◽  
Author(s):  
J. E. Woodward ◽  
M. A. Batla ◽  
P. A. Dotray ◽  
T. A. Wheeler ◽  
T. A. Baughman
Keyword(s):  
Weed Management ◽  
Tap Water ◽  
The United States ◽  
Plant Diseases ◽  
Weed Species ◽  
Sclerotinia Minor ◽  
Ipomoea Hederacea ◽  
First Report ◽  
Sclerotinia Blight ◽  
Pathogenicity Tests

Sclerotinia blight, caused by the soilborne fungus Sclerotinia minor Jagger, is a major disease of peanut (Arachis hypogaea L.) in parts of west Texas. Previous reports have indicated that annual weed species may serve as collateral hosts for S. minor (2). Several Ipomoea spp. are commonly found in peanut fields throughout the region. In September of 2007, Ipomoea hederacea and I. coccinea plants with bleached, shredded stems, and signs of black sclerotia were collected from a field known to be infested with S. minor. Symptomatic stem sections were rinsed in tap water, surface disinfested in 0.5% sodium hypochlorite for 1 min, air dried, and plated on potato dextrose agar (PDA). Pure cultures of S. minor consisting of white, fluffy mycelia and small (<2 mm), black, irregular sclerotia were consistently recovered. Pathogenicity tests were conducted by wound-inoculating healthy I. hederacea and I. coccinea transplants (n = 3) with agar plugs obtained from the edges of actively growing S. minor cultures. Plants were incubated in a dew chamber at 20°C and 95% relative humidity for 5 days. Plants inoculated with sterile PDA plugs served as controls (n = 3). A similar test was conducted using the susceptible peanut cultivar Flavorunner 458. Characteristic symptoms of Sclerotinia blight (3) were observed on all inoculated weed and peanut plants; whereas, the controls remained healthy. Pathogenicity tests were repeated with similar results. Cultures of S. minor were obtained from all symptomatic tissues, fulfilling Koch's postulates. These results indicate that I. hederacea and I. coccinea are additional hosts of S. minor and that sclerotia produced on infected plants can significantly augment soil inoculum. S. minor has been observed to infect I. batatas seedlings in New Jersey (1); however, this to our knowledge is the first report of S. minor infecting Ipomoea spp. in Texas. Therefore, weed management should inevitability be a part of disease management strategies for the control of Sclerotinia blight in peanut. References: (1) Anonymous. Index of Plant Diseases in the United States. USDA Handb. No. 165, 1960. (2) J. E. Hollowell et al. Plant Dis. 87:197, 2003. (3) D. M. Porter and H. A. Melouk. Sclerotinia blight. Page 34 in: Compendium of Peanut Diseases. 2nd ed. N. Kokalis-Burelle et al., eds. The American Phytopathologicial Society, St. Paul, MN, 1997.

scholarly journals First Report of Sclerotium rolfsii on Catharanthus roseus

Plant Disease ◽  
2000 ◽  
Vol 84 (2) ◽  
pp. 200-200
Author(s):  
G. E. Holcomb
Keyword(s):  
Catharanthus Roseus ◽  
Fungal Pathogen ◽  
Baton Rouge ◽  
Sclerotium Rolfsii ◽  
The United States ◽  
Madagascar Periwinkle ◽  
Basal Stem Rot ◽  
First Report ◽  
Pathogenicity Tests ◽  
Stem Necrosis

Wilt, blight, and stem necrosis were observed on Catharanthus roseus (L.) G. Don ‘Mediterranean Deep Rose’ (MDR) plants (Madagascar or rose periwinkle) in August 1999 at Burden Research Plantation in Baton Rouge, LA. MDR was the only prostrate-form cultivar and the only cultivar of 11 that was diseased. Twelve of twenty-four plants of cv. MDR were killed in the trial planting. White mycelia and small (1 mm diameter) light brown sclerotia were present at the base of infected plants. The suspect fungus was isolated consistently on acidified water agar and maintained on acidified potato dextrose agar (APDA). Pathogenicity tests were done by pipetting 1 ml of blended inoculum (contents of one 7-day-old plate culture grown on APDA in 100 ml of deionized water) at the base of nine 15-cm-tall Madagascar periwinkle plants. Inoculated and noninoculated plants were held in a dew chamber for 3 days at 28°C and placed in a greenhouse where temperatures ranged between 25 and 31°C. All inoculated plants showed wilt, blight, and basal stem rot after 3 days and were dead after 10 days. Noninoculated plants remained symptomless. The fungal pathogen was identified as Sclerotium rolfsii Sacc. and was reisolated from inoculated plants. The fungus was previously reported on Lochnera rosea (L.) Rchb. (=C. roseus) from Taiwan (1). This is the first report of the occurrence of S. rolfsii on Madagascar periwinkle in the United States. Reference: (1) K. Goto. Trans. Nat. Hist. Soc. Formosa 23:37, 1933.

scholarly journals First Report of Anthracnose of Lentil Incited by Colletotrichum truncatum in Bulgaria

Plant Disease ◽  
1998 ◽  
Vol 82 (1) ◽  
pp. 128-128 ◽  
Author(s):  
W. J. Kaiser ◽  
M. Mihov ◽  
F. J. Muehlbauer ◽  
R. M. Hannan
Keyword(s):  
Severe Infection ◽  
Plant Introduction ◽  
The United States ◽  
Field Trials ◽  
Colletotrichum Truncatum ◽  
Low Frequencies ◽  
First Report ◽  
Pure Cultures ◽  
Pathogenicity Tests ◽  
Stem Lesions

In June 1992 and 1995, anthracnose of lentil (Lens culinaris Medik.) incited by Colletotrichum truncatum (Schwein.) Andrus & W. D. Moore was widespread in field trials at the Institute for Wheat and Sunflower ‘Dobroudja’ near General Toshevo in northeastern Bulgaria. Lesions on the leaves, stems, and pods were usually white to grayish on younger plants, often turning brown as plants matured. Severe infection usually resulted in dieback and/or death of plants. Acervuli containing spores and dark setae were observed within lesions, and conidia from the acervuli produced pure cultures of C. truncatum. Conidia were hyaline, onecelled, falcate to nearly straight with a prominent clear area in the center of highly granular cytoplasm, and measured 17.6 to 19.8 × 4.4 μm. C. truncatum was seed-borne in naturally infected lentil cv. Tadjikskaya 95 at low frequencies (<2%). Koch's postulates were fulfilled by inoculating the foliage of lentil cvs. Brewer and Pardina and reisolating the fungus from stem and petiole lesions. In pathogenicity tests, three isolates of C. truncatum from the foliage and seeds of lentil caused severe symptoms on inoculated lentil cvs. Brewer and Pardina, similar to those observed on diseased lentils in Bulgaria. The fungus also caused moderate symptoms on inoculated faba bean (Vicia faba L.) and pea (Pisum sativum L.), and light symptoms on inoculated chickpea (Cicer arietinum L.). In 1995, 258 USDA Plant Introduction (PI) accessions from the USDA lentil core collection were screened in replicated trials in northeastern Bulgaria and disease symptoms were observed in >90% of the lines. Anthracnose severity ranged from light to severe. A few accessions appeared to have acceptable levels of resistance to the disease. These included accessions from Iran (PI 431714 and 431717) and Spain (PI 533693). Also that year, C. truncatum was isolated from stem lesions of naturally infected bitter vetch (Vicia ervilia (L.) Willd.) at the Institute for Wheat and Sunflower ‘Dobroudja’. The disease in Bulgaria appears to be identical to one causing anthracnose of lentil in Canada (1) and the United States (2). This is the first report of C. truncatum causing anthracnose of lentil in Bulgaria. References: (1) R. A. A. Morrall. Plant Dis. 72:994, 1988. (2) J. R. Venette et al. Plant Dis. 78:1216, 1994.

scholarly journals First Report of Sclerotinia Blight Caused by Sclerotinia sclerotiorum on Petunia × hybrida in Italy

Plant Disease ◽  
2009 ◽  
Vol 93 (12) ◽  
pp. 1353-1353 ◽  
Author(s):  
A. Garibaldi ◽  
D. Bertetti ◽  
P. Pensa ◽  
M. L. Gullino
Keyword(s):  
United States ◽  
Relative Humidity ◽  
Sclerotinia Sclerotiorum ◽  
Petunia Hybrida ◽  
Ornamental Plants ◽  
Its Region ◽  
The United States ◽  
First Report ◽  
Potted Plants ◽  
Sclerotinia Blight

Petunia × hybrida (Solanaceae) includes several hybrids that are grown as ornamental plants and are very much appreciated for their long-lasting flowering period. During the spring of 2009, extensive wilting was observed on 2-month-old potted plants of Petunia × hybrida cv. Sanguna Lilac Vein grown in a commercial glasshouse near Albenga (northern Italy). First symptoms included stem necrosis and darkening and withering of leaves. Wilt occurred a few days after the appearance of the first symptoms. Infected plants were characterized by the presence of soft, watery tissues. In the presence of high relative humidity, lesions became covered with a whitish mycelium and irregular, dark gray sclerotia (3.0 to 6.5 × 2.0 to 5.0 mm, average 4.8 × 3.3 mm) were produced on the mycelium. Diseased tissue was surface sterilized for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 mg/l of streptomycin sulfate. Sclerotinia sclerotiorum (Lib.) de Bary (3) was consistently recovered from infected stem pieces. Sclerotia produced on PDA measured 2.0 to 6.0 × 1.5 to 5.0 mm (average 3.9 × 3.1) mm. The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 548-bp segment showed a 100% homology with the sequence of S. sclerotiorum. The nucleotide sequence has been assigned GenBank Accession No. GQ375746. Pathogenicity of one isolate obtained from sclerotia of infected plants was confirmed by inoculating three 90-day-old plants belonging to cv. Sanguna Lilac Vein transplanted in 22-cm-diameter pots in a glasshouse in a sphagnum peat/pomix/pine bark/clay (50:20:20:10) mix. Inoculum that consisted of 2 g/liter of substrate of wheat kernels infested with mycelium and sclerotia was placed in the soil and around the base of each plant. Three noninoculated plants served as controls. Plants were maintained in greenhouse at temperatures ranging between 22 and 26°C and relative humidity >90%. The inoculation trial was carried out twice. All inoculated plants developed leaf yellowing by 20 days after soil infestation. White, cottony mycelium and dark sclerotia developed on stems and at the base of all inoculated plants. Eventually, infected plants wilted. Control plants remained symptomless. S. sclerotiorum was reisolated from the stems of inoculated plants. To our knowledge, this is the first report of S. sclerotiorum on Petunia × hybrida in Italy. The disease has been previously reported on Petunia × hybrida in Bermuda (2) and the United States (4). References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997 (2) R. M. Brien. N.Z. J. Sci. Tech., A, 24, 62, 1942. (3) N. F. Buchwald. Kongl. Veterisk Landb. Aarssk. 75, 1949. (4) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989.

scholarly journals First Report of Sclerotinia sclerotiorum Infecting Peanut in Texas

Plant Disease ◽  
2008 ◽  
Vol 92 (10) ◽  
pp. 1468-1468 ◽  
Author(s):  
J. E. Woodward ◽  
C. Nui ◽  
R. J. Wright ◽  
M. A. Batla ◽  
T. A. Baughman
Keyword(s):  
Block Design ◽  
Molecular Study ◽  
The United States ◽  
Disease Diagnosis ◽  
Outer Edge ◽  
Regional Survey ◽  
Blast Search ◽  
Sclerotinia Blight ◽  
Pathogenicity Tests ◽  
Petri Dishes

Peanut (Arachis hypogaea L.) is grown extensively in several counties in West Texas. Sclerotinia blight, caused by the soilborne fungus Sclerotinia minor Jagger, is an increasingly important disease throughout this region. In September of 2007, diseased peanut plants (cv. Tamrun OL02) exhibiting symptoms of Sclerotinia blight (2,4) were collected from a commercial farm in Gaines County during a regional survey. Infected stem sections were surface disinfested in 0.5% sodium hypochlorite for 1 min, air dried, and placed in petri dishes containing water agar. Hyphae were subsequently transferred to petri dishes containing potato dextrose agar (PDA) after 3 days of incubation at room temperature. Pure cultures formed abundant, aerial, white mycelia, which later became darkly pigmented. Black, spherical to elongated sclerotia, 3.8 ± 0.8 mm, formed on the outer edge of petri dishes after 1 week. These characteristics are consistent with S. sclerotiorum (Lib.) de Bary (1,2). Pathogenicity tests were conducted by inoculating stems of greenhouse-grown peanut plants (cvs. Tamrun OL02, n = 4 and Flavorrunner 458, n = 4) with PDA plugs containing S. sclerotiorum. Mounting pins were used to create a shallow wound and affix inoculum plugs to stems. Control plants (n = 4) were inoculated with noncolonized PDA plugs. Plants were placed in a dew chamber at 20°C and 95% relative humidity in a randomized complete block design. The experiment was conducted two times. Symptoms identical to those observed on the original plant specimens were observed after 3 days on all inoculated plants; the controls remained healthy. Darkly pigmented cultures of S. sclerotiorum were consistently reisolated from all symptomatic stem sections. Fungal DNA was extracted from mycelia and sclerotia with a Qiagen DNeasy Plant Mini kit (Valencia, CA) and amplified by PCR using three S. sclerotiorum-specific primer pairs (3). PCR products for three replicates (two from mycelia and one from sclerotia) were sequenced and subjected to a NCBI BLAST search of highly similar sequences (megablast). The BLAST search revealed that our sequences are highly similar only with reported sequences of S. sclerotiorum. Sequences generated from three primer pairs in this study were 99, 95, and 95% homologous to S. sclerotiorum Accessions Nos. AF377925.1, AF377919.1, and AF377904.1 over 373, 376, and 300 bp of aligned sequence, respectively. Results from the pathogenicity tests and molecular study confirm that the S. sclerotiorum isolate obtained in this study is capable of inciting Sclerotinia blight of peanut. While S. minor is the primary causal agent of the disease, recent reports indicate that S. sclerotiorum is becoming more prevalent throughout the peanut-producing regions of the United States (2,4), and must therefore be considered in disease diagnosis. References: (1) L. M. Kohn. Phytopathology 69:881, 1979. (2) S. Sanogo and N. Puppala. Plant Dis. 91:1077, 2007. (3) C. Sirjusingh and L. M. Kohn. Mol. Ecol. Notes 1:267, 2001. (4) J. E. Woodward et al. Plant Dis. 90:111, 2006.

scholarly journals First Report of Stem Canker of Salsola tragus Caused by Diaporthe eres in Russia

Plant Disease ◽  
2009 ◽  
Vol 93 (1) ◽  
pp. 110-110 ◽  
Author(s):  
T. Kolomiets ◽  
Z. Mukhina ◽  
T. Matveeva ◽  
D. Bogomaz ◽  
D. K. Berner ◽  
...  
Keyword(s):  
United States ◽  
Biological Control ◽  
Biological Control Agent ◽  
Aqueous Suspension ◽  
Stem Canker ◽  
The United States ◽  
Invasive Weed ◽  
Voucher Specimen ◽  
First Report ◽  
Stem Lesions

Salsola tragus L. (Russian thistle) is a problematic invasive weed in the western United States and a target of biological control efforts. In September of 2007, dying S. tragus plants were found along the Azov Sea at Chushka, Russia. Dying plants had irregular, necrotic, canker-like lesions near the base of the stems and most stems showed girdling and cracking. Stem lesions were dark brown and contained brown pycnidia within and extending along lesion-free sections of the stems and basal portions of leaves. Diseased stems were cut into 3- to 5-mm pieces and disinfested in 70% ethyl alcohol. After drying, stem pieces were placed into petri dishes on the surface of potato glucose agar. Numerous, dark, immersed erumpent pycnidia with a single ostiole were observed in all lesions after 2 to 3 days. Axenic cultures were sent to the Foreign Disease-Weed Science Research Unit, USDA, ARS, Ft. Detrick, MD for testing in quarantine. Conidiophores were simple, cylindrical, and 5 to 25 × 2 μm (mean 12 × 2 μm). Alpha conidia were biguttulate, one-celled, hyaline, nonseptate, ovoid, and 6.3 to 11.5 × 1.3 to 2.9 μm (mean 8.8 × 2.0 μm). Beta conidia were one-celled, filiform, hamate, hyaline, and 11.1 to 24.9 × 0.3 to 2.5 μm (mean 17.7 × 1.2 μm). The isolate was morphologically identified as a species of Phomopsis, the conidial state of Diaporthe (1). The teleomorph was not observed. A comparison with available sequences in GenBank using BLAST found 528 of 529 identities with the internal transcribed spacer (ITS) sequence of an authentic and vouchered Diaporthe eres Nitschke (GenBank DQ491514; BPI 748435; CBS 109767). Morphology is consistent with that of Phomopsis oblonga (Desm.) Traverso, the anamorph of D. eres (2). Healthy stems and leaves of 10 30-day-old plants of S. tragus were spray inoculated with an aqueous suspension of conidia (1.0 × 106 alpha conidia/ml plus 0.1% v/v polysorbate 20) harvested from 14-day-old cultures grown on 20% V8 juice agar. Another 10 control plants were sprayed with water and surfactant without conidia. Plants were placed in an environmental chamber at 100% humidity (rh) for 16 h with no lighting at 25°C. After approximately 24 h, plants were transferred to a greenhouse at 20 to 25°C, 30 to 50% rh, and natural light. Stem lesions developed on three inoculated plants after 14 days and another three plants after 21 days. After 70 days, all inoculated plants were diseased, four were dead, and three had more than 75% diseased tissue. No symptoms occurred on control plants. The Phomopsis state was recovered from all diseased plants. This isolate of D. eres is a potential biological control agent of S. tragus in the United States. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI 878717). Nucleotide sequences for the ribosomal ITS regions (ITS 1 and 2) were deposited in GenBank (Accession No. EU805539). To our knowledge, this is the first report of stem canker on S. tragus caused by D. eres. References: (1) B. C. Sutton. Page 569 in: The Coelomycetes. CMI, Kew, Surrey, UK, 1980. (2) L. E. Wehmeyer. The Genus Diaporthe Nitschke and its Segregates. University of Michigan Press, Ann Arbor, 1933.

scholarly journals Characterization of Leaf Spot Pathogens from Several Spinach Production Areas in the United States

Plant Disease ◽  
2020 ◽  
Vol 104 (7) ◽  
pp. 1994-2004
Author(s):  
Bo Liu ◽  
Larry Stein ◽  
Kimberly Cochran ◽  
Lindsey J. du Toit ◽  
Chunda Feng ◽  
...  
Keyword(s):  
United States ◽  
South Carolina ◽  
Leaf Spot ◽  
The United States ◽  
Leaf Damage ◽  
Leaf Spots ◽  
Pathogenicity Tests ◽  
Agar Media ◽  
Production Areas

Leaf spot diseases have become a major concern in spinach production in the United States. Determining the causal agents of leaf spots on spinach, their prevalence and pathogenicity, and fungicide efficacy against these pathogens is vital for effective disease management. Spinach leaves with leaf spots were collected from Texas, California, Arizona, and South Carolina from 2016 to 2018, incubated in a moist chamber, and plated on potato dextrose and tryptic soy agar media. Fungal and bacterial colonies recovered were identified based on morphology and sequence analysis of the internal transcribed spacer rDNA and 16S rRNA, respectively. Two predominant genera were isolated: (i) Colletotrichum spp., which were identified to species based on sequences of both introns of the glutamate synthetase (GS-I) and glyceraldehyde-3-phosphate dehydrogenase (gapdh-I) genes; and (ii) Stemphylium spp., identified to species based on sequences of the gapdh and calmodulin (cmdA) genes. Anthracnose (Colletotrichum spinaciae) and Stemphylium leaf spot (Stemphylium vesicarium and S. beticola) were the predominant diseases. Additional fungi recovered at very limited frequencies that were also pathogenic to spinach included Colletotrichum coccodes, C. truncatum, Cercospora beticola, and Myrothecium verrucaria. All of the bacterial isolates were not pathogenic on spinach. Pathogenicity tests showed that C. spinaciae, S. vesicarium, and S. beticola caused significant leaf damage. The fungicides Bravo WeatherStik (chlorothalonil), Dithane F-45 (mancozeb), Cabrio (pyraclostrobin), and Merivon (fluxapyroxad and pyraclostrobin) were highly effective at reducing leaf spot severity caused by an isolate of each of C. spinaciae and S. vesicarium, when inoculated individually and in combination.

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