First Report of Phytophthora cactorum Causing Crown Rot of Shepherdia × utahensis in the United States

Phytophthora cactorum causes crown rot of strawberry (Fragaria × ananassa) (2), a disease that has been particularly severe during the last 5 years in the southeastern United States. In the fall of 2001, strawberry plants (cv. Camarosa) in a field in Lexington County, South Carolina exhibited typical crown rot symptoms (2) 1 to 2 weeks after transplanting, even though plants had been drenched with mefenoxam (Ridomil Gold; Syngenta Crop Protection, Greensboro, NC) immediately after transplanting. Initially, we observed leaves that had marginal necrosis, were smaller than normal, and were discolored. Soon after, diseased plants appeared stunted and unthrifty compared with other plants in the field, and some of these plants eventually wilted and died. Severely affected plants had necrotic roots and decayed crowns. Ten symptomatic plants were collected for isolation. In the laboratory, root and crown tissues were rinsed in running tap water and blotted dry, small pieces of necrotic tissue were placed aseptically on PAR-V8 selective medium (1), and isolation plates were placed at 20°C in the dark for up to 7 days. P. cactorum was recovered from six plants. Isolates produced characteristic asexual and sexual structures directly on the isolation plates (i.e., papillate sporangia on sympodial sporangiophores and oospores with paragynous antheridia) (2). A single hypha of an isolate from each plant was transferred to fresh PAR-V8, and pure cultures were stored on cornmeal agar in glass vials at 15°C in the dark. All six isolates from the Lexington County field and nine other isolates of P. cactorum from strawberry (three from South Carolina, three from North Carolina, and three from Florida) were tested for sensitivity to mefenoxam on fungicide-amended medium. Mefenoxam was added to 10% clarified V8 juice agar (cV8A) after autoclaving so the concentration in the medium was 100 ppm. Agar plugs from active colonies were transferred to mefenoxam-amended and nonamended cV8A (three replicates per treatment), plates were placed at 25°C in the dark for 3 days, and linear mycelium growth was measured. All six isolates from Lexington County were highly resistant to mefenoxam with mycelium growth relatively unrestricted on mefenoxam-amended medium (73 to 89% of that on nonamended medium). In comparison, the other nine isolates were sensitive to mefenoxam with mycelium growth severely restricted by 100 ppm of mefenoxam (0 to 7% of that on nonamended medium). To our knowledge, this is the first report of mefenoxam resistance in P. cactorum on strawberry or any other crop in the United States and elsewhere. Because mefenoxam is the primary fungicide used to manage Phytophthora crown rot in the southeastern United States, resistance may limit use of this fungicide in strawberry production. References: (1) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (2) E. Seemüller. Crown rot. Pages 50–51 in: Compendium of Strawberry Diseases, 2nd ed. J. L. Maas, ed. The American Phytopathological Society, St. Paul, MN, 1998.

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First Report of Macrophomina Crown Rot Caused by Macrophomina phaseolina on Basil in the United States

Plant Disease ◽

10.1094/pdis-10-20-2300-pdn ◽

2021 ◽

Vol 105 (4) ◽

pp. 1218-1218

Author(s):

S. T. Koike ◽

H. Stanghellini ◽

A. Burkhardt

Keyword(s):

United States ◽

Macrophomina Phaseolina ◽

The United States ◽

Crown Rot ◽

First Report

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First Report of Stem and Crown Rot of Garbanzo Caused by Sclerotinia minor in the United States and by Sclerotinia sclerotiorum in Arizona

Plant Disease ◽

10.1094/pdis.2000.84.11.1250a ◽

2000 ◽

Vol 84 (11) ◽

pp. 1250-1250 ◽

Cited By ~ 4

Author(s):

M. E. Matheron ◽

M. Porchas

Keyword(s):

United States ◽

Cicer Arietinum ◽

Soil Surface ◽

The United States ◽

Crown Rot ◽

Sclerotinia Minor ◽

First Report ◽

Initial Symptoms ◽

Stem Necrosis ◽

White Mycelium

In March 2000, plants began to die within two garbanzo (Cicer arietinum L.) fields about 48 km apart in southwestern Arizona. Initial symptoms included wilting of leaves and stem necrosis on individual branches, followed by entire plant necrosis and death. White mycelium was present on plant stems near the soil surface. In one field, small black irregularly shaped sclerotia (1 mm in diameter) were present on the infected stem surface along with the white mycelia, whereas in the other field the associated sclerotia were of similar shape but larger (5 to 6 mm in diameter). Isolation from diseased garbanzo stem tissue from the respective fields yielded Sclerotinia minor, which produced small sclerotia when cultured on potato-dextrose agar and S. sclerotiorum, which produced the typical larger sclerotia of this species. To fulfill Koch's postulates, healthy plants and associated soil from a garbanzo field with no evidence of infection by Sclerotinia were removed with a shovel and transferred into a series of 8-liter plastic pots. After transporting back to the laboratory, some of the plants were inoculated by wounding stems with a 5-mm-diameter cork borer, placing an agar disk containing either S. minor or S. sclerotiorum onto each wound, securing the agar disk to the stem with plastic tape, then incubating the plants at 25°C for 7 days. Control plants were treated similarly except that agar disks did not contain Sclerotinia. Stems inoculated with S. minor or S. sclerotiorum developed symptoms of wilt and necrosis, including the appearance of white mycelium and sclerotia on the stem surface, whereas control plants remained healthy. S. minor or S. sclerotiorum were recovered from garbanzo stems inoculated with the respective species of the pathogen. Sclerotinia leaf drop, which can be caused by S. minor or S. sclerotiorum on lettuce in Arizona, had been observed in both fields previously. Garbanzo fields in Arizona usually are watered by furrow irrigation. Disease was most severe in areas of the garbanzo fields that were heavily irrigated with resultant wetting of tops of plant beds. Proper management of irrigation water and avoidance of establishing a garbanzo planting in fields following lettuce could help reduce future losses from these pathogens. S. minor previously had been reported as a pathogen on Cicer arietinum from the island of Sardinia (2); however, this is apparently the first report of the pathogen on garbanzo other than in Sardinia. S. sclerotiorum has been reported as a pathogen on this host in several countries including the United States (California) (1) but not previously in the state of Arizona. References: (1) I. W. Buddenhagen, F. Workneh, and N. A. Bosque-Perez. Int. Chickpea Newsl. 19:9–10, 1988. (2) F. Marras. Rev. Appl. Mycol. 43:112, 1964.

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First Report of Phytophthora nicotianae Causing Crown Rot of Strawberry in the United States

Plant Disease ◽

10.1094/pdis-08-17-1333-pdn ◽

2018 ◽

Vol 102 (7) ◽

pp. 1463-1463 ◽

Cited By ~ 2

Author(s):

M. V. Marin ◽

T. Seijo ◽

M. S. Oliveira ◽

E. Zuchelli ◽

J. Mertely ◽

...

Keyword(s):

United States ◽

The United States ◽

Phytophthora Nicotianae ◽

Crown Rot ◽

First Report

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First Report of Crown Rot of Gazania rigens Caused by Sclerotinia sclerotiorum in Louisiana

Plant Disease ◽

10.1094/pd-90-1114a ◽

2006 ◽

Vol 90 (8) ◽

pp. 1114-1114

Author(s):

G. E. Holcomb

Keyword(s):

United States ◽

Sclerotinia Sclerotiorum ◽

Standard Error ◽

The United States ◽

Crown Rot ◽

First Report ◽

Bedding Plant ◽

Leaf Yellowing ◽

Crown Tissue ◽

Pathogenicity Tests

Gazania rigens (L.) (treasure flower, Asteraceae) is grown as a winter and summer annual bedding plant in Louisiana and the lower southern United States. In March 2006, cv. Kiss Mix was observed in a wholesale nursery with symptoms of leaf yellowing, wilt, crown rot, and death. White mycelia and black sclerotia were present on some infected and dead plants. The plants had been grown outdoors and approximately 2% of 1,120 plants had been lost. Petiole and crown tissue from infected plants were surface disinfected in 70% ethyl alcohol, and sections were placed on acidified potato dextrose agar (PDA). A fungus that produced white mycelia and black sclerotia consistently grew from tissue pieces. Other characteristics included production of numerous sclerotia (32 to 71 per dish from 10 dishes) that were oval to oblong and formed in a ring at the periphery of culture dishes. Sclerotia measured 3 to 7 mm long (mean = 4.4, standard error = 0.15, N = 50) × 2 to 4 mm wide (mean = 3.0, standard error = 0.06, N = 50). Cells of sclerotial rinds were globose and lacked erect tomentum hyphae (1). Growth rate of the fungus at 26°C on PDA ranged from 1.3 to 3.1 cm/day (mean = 2.2, standard error = 0.05, N = 45) and mycelia covered the dishes after 3 days (2). On the basis of these characteristics, the fungus was identified as Sclerotinia sclerotiorum (Lib.) de Bary. Fungal inoculum for pathogenicity tests was grown on twice-sterilized wheat grains and 1 g of 10-day-old inoculum, consisting of fungus mycelia and sclerotia, was placed at the base of six G. rigens cv. Daybreak Mix plants. Inoculated and noninoculated control plants were placed in a dew chamber held at 22°C for 48 h and then moved to a greenhouse where temperatures ranged from 20 to 25°C. Leaf yellowing, wilt, and crown rot developed after 3 to 4 days on all inoculated plants followed by death after 6 days. S. sclerotiorum was reisolated from all inoculated plants. Noninoculated plants remained healthy. Sclerotinia crown rot of G. rigens was first reported in the United States from California (3) and has also been reported from Italy and Argentina (4). To our knowledge, this is the first report of Sclerotinia crown rot on G. rigens in Louisiana. References: (1) L. M. Kohn. Phytopathology 69:881, 1979. (2) G. Li et al. Mycol. Res. 104:232, 2000. (3) V. M. Muir and A. H. McCain. Calif. Plant Pathol. 16:1, 1973. (4) S. M. Wolcan. J. Plant Path. 86:263, 2004.

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First Report of Crown Rot, Stem Rot, and Root Rot Caused by Binucleate Rhizoctonia AG-G on Viburnum tinus in Italy

Plant Disease ◽

10.1094/pdis-93-4-0433b ◽

2009 ◽

Vol 93 (4) ◽

pp. 433-433 ◽

Cited By ~ 2

Author(s):

G. Polizzi ◽

D. Aiello ◽

A. Vitale ◽

E. Lahoz ◽

R. Nicoletti ◽

...

Keyword(s):

United States ◽

Root Rot ◽

The United States ◽

Crown Rot ◽

Fluorescent Light ◽

First Report ◽

Binucleate Rhizoctonia ◽

Potted Plants ◽

Rdna Its ◽

Safranin O

Laurustinus (Viburnum tinus L.), native to the Mediterranean Region, is an evergreen shrub belonging to the Caprifoliaceae that is commonly cultured as an ornamental shrub or small tree. During the summer and autumn of 2007 and 2008, a widespread yellowing, partial foliar necrosis, or death of the whole plant was observed on 3- to 4-year-old potted plants of V. tinus in a commercial nursery in eastern Sicily (Italy). More than 20% of the plants showed disease symptoms. Infected roots, crowns, and stems turned dark brown, leaves gradually became necrotic, and infected plants were often killed. Diseased tissues were disinfested for 1 min in 1% NaOCl, rinsed in sterile water, plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 mg/liter, and then incubated at 25°C. A binucleate Rhizoctonia (BNR) species was consistently isolated from affected tissue of Laurustinus. Fungal colonies were initially white, then turned light brown or brown with age, and formed irregularly shaped, light brown sclerotia after 10 days. Hyphal cells were determined to be binucleate when stained with 1% safranin O and 3% KOH solution (1) and examined with a microscope at ×400. Anastomosis groups were determined by pairing isolates on 2% water agar in petri plates (4). Pairings were made with tester strains of binucleate Rhizoctonia AG-A through AG-S, except AG-J and AG-M. Anastomosis was observed only with tester isolates of AG-G. The rDNA-ITS of two isolates of BNR (DISTEF-Vt 31 and DISTEF-Vt 32) was sequenced (GenBank Accession Nos. AB478783 and AB478784, respectively) (3). The sequence from these two isolates exhibited 100% homology with BNR AG-G (GenBank Accession No. AY927334). Pathogenicity tests were conducted on potted, healthy, 6-month-old laurustinus. Twenty plants were inoculated by placing 1-cm2 plugs of PDA from 5-day-old mycelial cultures near the base of the stem. The same number of plants was treated with 1-cm2 PDA plugs as control. Plants were kept at 25°C and 95% relative humidity with a 12-h fluorescent light/dark regimen. Stem, crown, and root rot symptoms, identical to ones observed in nursery, appeared 20 days after inoculation, and all the inoculated plants showed symptoms within 1 month. Control plants remained healthy. Binucleate Rhizoctonia was reisolated from symptomatic tissues, completing Koch's postulates. R. solani was previously reported on Viburnum sp. in the United States (2). To our knowledge, this is the first report of binucleate Rhizoctonia causing disease on V. tinus. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) D. F. Farr et al. Page 1252 in: Fungi on Plants and Plant Products in the United States. The American Phytopathological Society. St. Paul, MN, 1989. (3) M. Hyakumachi et al. Phytopathology 95:784, 2005. (4) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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First Report of Pathogenicity of Fusarium sporotrichioides and Fusarium acuminatum on Sunflowers in the United States

Plant Health Progress ◽

10.1094/php-2010-0915-02-br ◽

2010 ◽

Vol 11 (1) ◽

pp. 42 ◽

Cited By ~ 4

Author(s):

F. Mathew ◽

B. Kirkeide ◽

T. Gulya ◽

S. Markell

Keyword(s):

United States ◽

Helianthus Annuus ◽

The United States ◽

Fusarium Sporotrichioides ◽

Charcoal Rot ◽

Koch’S Postulates ◽

First Report ◽

Fusarium Acuminatum ◽

Helianthus Annuus L ◽

Koch's Postulates

Widespread infection of charcoal rot was observed in a commercial sunflower field in Minnesota in September 2009. Based on morphology, isolates were identified as F. sporotrichioides and F. acuminatum. Koch's postulates demonstrated pathogencity of both species. To our knowledge, this is the first report of F. sporotrichoides and F. acuminatum causing disease on Helianthus annuus L. in the United States. Accepted for publication 23 August 2010. Published 15 September 2010.

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First Report of Wisteria vein mosaic virus in Wisteria sinensis in the United States of America

Plant Health Progress ◽

10.1094/php-2008-0818-01-br ◽

2008 ◽

Vol 9 (1) ◽

pp. 42 ◽

Cited By ~ 1

Author(s):

Rayapati A. Naidu ◽

Gandhi Karthikeyan

Keyword(s):

United States ◽

Mosaic Virus ◽

United States Of America ◽

The United States ◽

Home Gardens ◽

First Report ◽

Woody Perennial ◽

Wisteria Sinensis ◽

First Time ◽

Wisteria Vein Mosaic Virus

The ornamental Chinese wisteria (Wisteria sinensis) is a woody perennial grown for its flowering habit in home gardens and landscape settings. In this brief, the occurrence of Wisteria vein mosaic virus (WVMV) was reported for the first time in Chinese wisteria in the United States of America. Accepted for publication 18 June 2008. Published 18 August 2008.

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Expansion of Groundnut ringspot virus Host and Geographic Ranges in Solanaceous Vegetables in Peninsular Florida

Plant Health Progress ◽

10.1094/php-2011-0725-01-br ◽

2011 ◽

Vol 12 (1) ◽

pp. 34 ◽

Cited By ~ 6

Author(s):

Craig G. Webster ◽

William W. Turechek ◽

H. Charles Mellinger ◽

Galen Frantz ◽

Nancy Roe ◽

...

Keyword(s):

United States ◽

The United States ◽

Vegetable Production ◽

Viral Pathogen ◽

Geographic Ranges ◽

First Report ◽

Geographic Spread ◽

Wide Range ◽

Production Areas ◽

Solanaceous Plants

To the best of our knowledge, this is the first report of GRSV infecting tomatillo and eggplant, and it is the first report of GRSV infecting pepper in the United States. This first identification of GRSV-infected crop plants in commercial fields in Palm Beach and Manatee Counties demonstrates the continuing geographic spread of the virus into additional vegetable production areas of Florida. This information indicates that a wide range of solanaceous plants is likely to be infected by this emerging viral pathogen in Florida and beyond. Accepted for publication 27 June 2011. Published 25 July 2011.

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