First Report of Plumeria spp. Rust Caused by Coleosporium plumeriae in Louisiana and Malaysia and Catheranthus roseus, a New Host of this Rust.

Plumeria spp., native to tropical America, are popular small trees grown widely in tropical areas of the world and as potted plants elsewhere. P. rubra and P. obtusa cultivars and hybrids are most common. A rust disease of a Plumeria sp. (likely P. rubra based on pointed leaf tips, leaves more than 18 cm (7 inches) long, and high rust susceptibility) was observed in November 2008 and again in June 2009 on homeowner plants in Baton Rouge, LA. A survey of five Baton Rouge retail nurseries in September 2009 revealed that 87% (90 of 103) of the plumeria plants were heavily infected with rust. Early symptoms included numerous 1-mm chlorotic spots on adaxial leaf surfaces followed by leaf chlorosis, necrosis, and abscission. Uredinia were numerous, mostly hypophyllous and yellowish orange. Urediniospores were catenulate, orange en masse, verrucose, globose, ovoid, ellipsoidal or angular, and measured 21.8 to 41.9 × 16.4 to 32.8 µm (average 29.4 × 22.6 µm). The rust was identified as Coleosporium plumeriae Pat. (= C. plumierae) (3). Teliospores were not found during this study. Pathogenicity tests were performed by spraying urediniospores (20,000/ml of deionized water) on three healthy Thai hybrid plumeria plants. Five leaves of each plant were misted with water and covered with plastic bags and three to five leaves were inoculated. Plants were held at 27°C for 27 h in a dew chamber and then moved outdoors. Typical rust symptoms and uredinia with urediniospores developed in 10 days on all inoculated leaves while noninoculated leaves remained healthy. Characteristics and spore measurements matched those of the rust from original infected plants. Additional plumeria rust inoculations were made to other Apocynaceae family members that included Allamanda cathartica, Catheranthus roseus (Madagascar periwinkle), Mandevilla splendens, Nerium oleander, and Vinca major. Catheranthus roseus was very susceptible to C. plumeriae with chlorotic leaf spots developing on the six inoculated plants after 8 days and uredinia with urediniospores appearing after 11 days. None of the other plant genera were susceptible to the rust. Plumeria rust was also observed on plumeria trees in urban landscapes in peninsular (Penang) and Bornean (Kota Kinabalu, Sabah) Malaysia in December 2007. To confirm identity, ~1,000 bp of nuclear rDNA 28S subunit from each (Lousiana, Penang, and Kota Kinabalu) was sequenced with rust-specific primers (1) and shared 100% identity (GenBank No. GU145555-6). Plumeria rust was first found on the island of Guadeloupe (3) and then spread to Central and South America. It has been known from Florida since 1960 under the synonym C. domingense (2), but has not been reported elsewhere in the continental United States. In more recent years, plumeria rust has spread to Hawaii, many Pacific islands, India, China, Taiwan, Thailand, Australia, and Nigeria (4). To our knowledge, this is the first report of plumeria rust from Louisiana and Malaysia and of susceptibility of another member of the Apocynaceae, Madagascar periwinkle, to C. plumeriae. Voucher material from Louisiana and Malaysia has been deposited in the Mycology Herbarium of Louisiana State University (LSUM). References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) Anonymous. Index of Plant Diseases in the United States. U.S. Dept. Agric. Handb. No. 165. Washington, D.C., 1960. (3) N. Patouillard. Bull. Soc. Mycol. Fr. 18:171, 1902. (4) C. To-Anun et al. Nat. Hist. J. Chulalongkorn Univ. 4:41, 2004.

First Report of Powdery Mildew on Azalea Caused by Erysiphe azaleae in Louisiana.

A group of five cv. Red Formosa azaleas (also known as cv. Dixie Beauty, an evergreen indica type of Rhododendron indicum) was observed with powdery mildew symptoms in Baton Rouge, LA in early March 2006. Symptoms included leaf distortion, purple leaf pigmentation at infection sites, and irregular necrotic areas. White, sparse, superficial fungal mycelium was present on both leaf surfaces. There was no active conidia production at this time and no cleistothecia were found on the old infected leaves. Infected plants were 5 years old and growing in heavy shade beneath a large deciduous oak tree. Two other groups of powdery mildew-free cv. Red Formosa, containing 6 and 11 plants each, were growing in mostly shade-free areas within 30 and 140 m, respectively, of the infected plants. Of 5,091 azaleas surveyed in and around Baton Rouge, only three other infected plants were found beside the original five. Among the plants surveyed were 167 additional cv. Red Formosa azaleas. The three additional infected azaleas, all the same unidentified indica type cultivar and growing in dense shade, showed severe leaf distortion and leaf drop. Conidia were produced abundantly on these plants in April and early May, but the teleomorph was not found. Pathogenicity tests were performed by rubbing leaves with sporulating powdery mildew from infected cv. Red Formosa plants on terminal leaves of two branches each of three 1-gallon-container plants of the same cultivar. A clear plastic bag containing a damp paper towel was placed over each inoculated branch for 48 h and then removed. Noninoculated branches on the same plants served as controls. Plants were maintained in a greenhouse (21 to 27°C). After 5 days, the first symptoms and signs of infection appeared on inoculated leaves in the form of purple pigment formation and white sporulating mycelia. After 12 days, terminal leaves on all inoculated branches showed symptoms and signs of powdery mildew, and after 18 days, leaf puckering and irregular necrotic spotting was common; purple pigmentation often outlined infected areas in which white mycelia and conidia production occurred. Some sporulation was present on petioles and some leaf drop occurred. The foliage on noninoculated branches remained disease free. Conidia from original infected plants were produced singly, ellipsoid to cylindric, lacked fibrosin bodies, and measured 27 to 54 µm long (mean = 37.4, standard error (SE) = 0.19, n = 102) × 15 to 23 µm wide (mean = 17.4, SE = 0.13, n = 102). Conidia sometimes formed short chains of two to four on inoculated plants held in the greenhouse. Conidiophores measured 77 to 123 µm long (mean = 106, SE = 1.1, n = 12) × 7 to 10 µm wide (mean = 8.9, SE = 0.26, n = 12) and had curved or twisted bases. Appressoria were multilobed. On the basis of these characters, the anamorph of the azalea powdery mildew was identified as Oidium ericinum Erikss. = Erysiphe (Microsphaera) azaleae (U. Braun) U. Braun & S. Takam. (1,2,4). To our knowledge, this is the first report on the occurrence of azalea powdery mildew in Louisiana. Powdery mildew is more common on deciduous than on evergreen azaleas and is more common in northern parts of the United States, especially in the Pacific Northwest (3). References: (1) U. Braun. Nova Hedwigia Suppl. 89:1, 1987. (2) U. Braun and S. Takamatsu. Schlechtendalia 4:5, 2000. (3) M. L. Daughtrey and D. M. Benson. Rhododendron diseases. Page 339 in: Diseases of Woody Ornamentals and Trees in Nurseries. R. K. Jones and D. M. Benson, eds. The American Phytopathological Society. St. Paul, MN, 2001. (4) A. J. Inman et al. J. Phytopathol. 148:17, 2000.

First Report of Downy Mildew on Greenhouse and Landscape Coleus Caused by a Peronospora sp. in Louisiana and New York.

In May 2005, two commercial greenhouse flower growers, one in Louisiana (LA) and one in New York (NY), submitted coleus, Solenostemon scutellarioides (L.) Codd, plants for diagnosis after observing stunted growth, inward curling and twisting of leaves, and leaf abscission on multiple cultivars. Downy mildew-like growth was observable with hand lens or a microscope on the abaxial leaf surfaces of affected plants. Irregular necrotic spotting was present on some, but not all, plants on which sporulation was evident. Microscopic examination of LA material led to tentative identification of the pathogen as Peronospora lamii A. Braun (2). The pale brown conidia ranged from 17 to 26 × 15 to 26 µm (average 23 × 19 µm). Conidiophores ranged from 345 to 561 × 9 to 15 µm. No oospores were found. Additional coleus plants with downy mildew were subsequently found in three retail nurseries in LA in early summer. In NY, infected coleus plants were observed in landscapes in Farmington, Rochester, Ithaca, and in two commercial greenhouses between August and October 2005. NY samples sent to the USDA/APHIS in Beltsville, MD were examined, and the fungus was found to have morphology consistent with P. lamii. Two pathogenicity trials were conducted in NY. Conidia were rubbed from an infected coleus leaf onto the leaves of six healthy potted coleus plants of five cultivars and two basil plants that were placed in a shaded plastic tent in the greenhouse where temperatures ranged from 17 to 22°C. A household humidifier was used to supply mist inside the tent for 5 h per day. Six noninoculated plants of each coleus cultivar and two basil plants, placed in the same environment, served as controls. Downy mildew sporulation and some curling and twisting of leaves were observed 14 days after inoculation on all inoculated plants for three of the five cultivars (Florida Rustic Orange, Aurora Peach, and Aurora Mocha). Cvs. Florida Sun Rose and Lava showed no symptoms or signs of downy mildew. An irregularly shaped brown lesion developed on one inoculated basil leaf, and downy mildew sporulation was evident on the abaxial surface 35 days after inoculation. All noninoculated control plants remained disease free. In a second trial, conidia were rinsed from infected coleus leaves and sprayed onto the abaxial leaf surfaces of three coleus cv. Aurora Mocha plants. Three noninoculated plants served as controls and all were placed in a humidity tent. Leaf twisting and downy mildew sporulation were observed 13 days later on all inoculated plants, and control plants showed no sporulation or symptoms. A downy mildew causing disease of greenhouse-grown basil in Europe, originally identified as P. lamii on the basis of morphology, has recently been reported to be taxonomically distinguishable from P. lamii when tested by molecular methods (1). ITS sequences of coleus downy mildew from NY and LA were nearly identical (99% homology) to those of basil downy mildew from Switzerland and Italy (1). To our knowledge, this is the first report of downy mildew occurrence on coleus. References: (1) L. Belbahri et al. Mycol. Res. 109:1276, 2005. (2) S. M. Francis. Peronospora lamii. Descriptions of Pathogenic Fungi and Bacteria. No. 688. CMI, Kew, England, 1981.

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

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.

First Report of Sclerotinia Stem Rot and Death of Osteospermum spp. Hybrid Cultivars Caused by Sclerotinia sclerotiorum in Louisiana.

Osteospermum spp. Hybrids, belong to Asteraceae, commonly called African daisy or cape daisy with over 214 named cultivars, are popular flowering plants grown as winter landscape plants in southern Louisiana. During January of 2005, plants growing in a wholesale nursery using polyethylene-film-covered greenhouses were observed with symptoms of wilt that began with tan stem lesions and progressed to stem rot, wilt, and plant death. Plants had been purchased out-of-state as rooted cuttings and transplanted to a commercial bark potting mix in 11.4-cm (4.5-in.) plastic pots. Signs of fungal infection included the presence of white cottony mycelium and black sclerotia. Disease incidence was 50% on cv. Soprano White but less than 1% among the four other cultivars being grown (Ostica Blue Eye, Ostica Pink, Lemon Symphony, and Soprano Purple). Differences in disease incidence among cultivars may have been due to differences in susceptibility since all were grown on the same greenhouse bench. Sclerotinia sclerotiorum was consistently isolated from sections of diseased stems that had been surfaced disinfested (30 to 60 s in 70% ethyl alcohol) and placed on acidified potato dextrose agar. Inoculum for pathogenicity tests consisted of mixed mycelia and sclerotia that had been grown on twice-sterilized wheat grain for 14 days. Ten flowering-age Osteospermum sp. plants of cv. Soprano White were inoculated with 1 g of inoculum placed at the base of each plant. One group of five plants was kept in a dew chamber at 22°C for 40 h after which they were removed to a greenhouse. The second group of five plants was placed in a single, plastic bag with the top left open and kept in the greenhouse. Ten noninoculated plants of the same cultivar served as controls with five kept in the dew chamber for 40 h and the other five held in a plastic bag in the greenhouse. Inoculated plants that had been held in the dew chamber developed stem lesions and rot after 2 days, wilted permanently after 5 days, and were desiccated and dead by day 7. Inoculated plants held in the bag in the greenhouse followed a similar disease development pattern but did not show wilt symptoms until 8 days after inoculation and were dead after 12 days. White cottony mycelium and black sclerotia developed on stems and at the base of all inoculated plants. S. sclerotiorum was reisolated from inoculated diseased plants. All noninoculated control plants remained disease free. An outbreak of this disease was previously reported on Osteospermum spp. planted along highways in southern California (1). To our knowledge, this is the first report of the disease in Louisiana and the first report of its occurrence in greenhouse production of Osteospermum spp. Reference: (1) H. S. Gill. Plant Dis. Rep. 59:82, 1975.

First Report of Southern Blight of Ruellia brittoniana Caused by Sclerotium rolfsii in Louisiana.

Ruellia brittoniana, Mexican petunia, is an herbaceous flowering perennial grown in hardiness zones 8 to 10 in the southern and western United States. Popular dwarf forms with flower colors of white, pink, and blue are used as ground covers and borders. In April of 2003, root and stem rot that caused plant death was observed on cv. Katie (dwarf form, pink flowers) at a wholesale nursery in southern Louisiana. Plants were growing in a vermiculite and sand mix. The grower had purchased the plants from an out-of-state source, and approximately one-half of 1,440 plants were dead or dying. Symptoms included wilt, basal stem rot, and root rot. Peripheral roots were covered with a white mycelial layer that contained white sclerotial initials and small, brown sclerotia. Fungal isolates from infected roots grown on potato dextrose agar (PDA) produced white mycelia and 1- to 2-mm-diameter dark brown sclerotia. Sclerotia were nearly round with smooth surfaces and distributed over the entire colony. Isolates were identified as Sclerotium rolfsii on the basis of mycelial characteristics and color, size, and distribution of sclerotia. Two-month-old seedlings (6 to 10 cm high) of R. brittoniana, from seed of cv. Katie, were used in pathogenicity tests. Inoculum was grown in 10-cm-diameter plastic, culture dishes on PDA medium. Blended inoculum was prepared from a single 1-week-old culture that was composed of mycelia and sclerotia and blended 4 to 6 s at high speed in 100 ml of distilled water. In test one, 5 ml of inoculum was placed at the base of each inoculated plant. In test two, a single 5-mm-diameter agar plug with mycelium plus four sclerotia was placed beside plant stems near soil line. In test three, 5 ml of blended inoculum was dripped on exposed roots after plants were removed from pots. In test four, exposed plant roots were dipped in the blended inoculum. Each test contained 10 inoculated plants, and 10 noninoculated plants served as controls. All plants were placed in a dew chamber maintained at 28°C for 2 days and then returned to a greenhouse to observe development of symptoms and signs of disease. In tests one and two, basal stem rot and wilt developed on inoculated plants after 2 days and after 5 to 8 days all were dead. Inoculated plants from tests three and four were alive 4 months after inoculation, but were showing symptoms including leaf yellowing and drop, moderate to severe root rot, and some plants had begun to show white mycelia and white sclerotial initials on peripheral roots by January 2004. All noninoculated plants remained healthy and S. rolfsii was reisolated from infected plants in each test. To my knowledge, this is the first report of S. rolfsii causing disease on R. brittoniana.

First Report of Petunia Blight Caused by Choanephora cucurbitarum in the United States.

A blight (wet rot) of petunia (Petunia ×hybrida Hort. Vilm.-Andr.) was observed in a wholesale propagation nursery in Baton Rouge, LA in September 2002. The grower reported that plants wilted and then completely rotted. The disease occurred during a period of hot, humid, and cloudy weather. Approximately 100 flats of flowering-age plants of cvs. Rose and White Madness were destroyed. No fungal sporulation was noticed on dead plants, but occasional strands of white mycelium were observed. The grower's use of azoxystrobin, iprodione, and thiophanate methyl plus mancozeb fungicides during current and past outbreaks of this disease did not prevent disease spread, but disease activity stopped after temperature and humidity dropped in early October. A fungus that produced white aerial mycelia that later developed light yellow areas and also black aerial spore masses was consistently isolated from diseased tissue placed on acidified potato dextrose agar (APDA). The fungus was identified as Choanephora cucurbitarum (Berk. & Ravenel) Thaxt. on the basis of cultural and morphological characteristics (3). Sporangiola were ellipsoid, pale brown to reddish brown with distinct longitudinal striations and measured 15 to 20 × 9 to 14 µm. Sporangiospores were broadly ellipsoid, pale brown to reddish brown, indistinctly striate with fine, hyaline polar appendages, and measured 16 to 34 × 7 to 12 µm. Spore measurements were within the range previously given for C.cucurbitarum (3). Pathogenicity tests were performed by misting a mixture of sporangiola and sporangiospores (25,000 to 70,000 per ml of water taken from 7- to 10-day-old cultures grown on APDA) on flowering-age petunia plants (cvs. Rose Madness, White Madness, and Dreams Pink). Tests were repeated twice. Inoculated plants and uninoculated control plants (2 to 4 of each treatment in each test) were held in a dew chamber at 28°C for 48 h and then moved to a greenhouse. Within 48 h after inoculation, plants developed water-soaked lesions on flowers, leaves, and stems, then wilted and rotted. Uninoculated plants remained disease free except for several that developed disease symptoms in the first test, apparently from the presence of natural inoculum on healthy-appearing plants that were obtained from the nursery where the disease was found. Koch's postulates were completed by reisolation of the pathogen from diseased inoculated plants. C. cucurbitarum (1) and C. infundibulifera (Curr.) Sacc. (2) have been reported to cause flower blight of petunia in the United States and whole plant blight (wet rot) of petunia in Japan (4). To our knowledge, this is the first report of C. cucurbitarum causing whole plant blight of petunia in the United States. References: (1) M. L. Daughtrey et al. Choanephora wet rot of poinsettia. Page 15 in: Compendium of Flowering Potted Plant Diseases. The American Phytopathological Society, St. Paul, MN, 1995. (2) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (3) P. M. Kirk. Mycological Paper 152:1, 1984. (4) J. Takeuchi and H. Horie. Jpn. J. Phytopathol. 66:72, 2000.

First Report of Web Blight Caused by Rhizoctonia solani on Catharanthus roseus in Louisiana.

Web (aerial) blight was observed in field plots of Catharanthus roseus (L.) G. Don (Madagascar periwinkle) during three consecutive summers at the Burden Research Center in Baton Rouge. Leaf spots formed first, followed by a general blighting of leaves and stems that resulted in circular areas of dead plants in the plots. Dead leaves were matted together but remained attached to plants. Mycelia, and occasionally small, brown sclerotia (1 to 3 mm) were observed on blighted foliage. During the first year, only prostrate-growing cultivars belonging to the Mediterranean series of C. roseus were infected, but in 2001 and 2002 upright-growing cultivars as well as those with prostrate growth habit became infected. The disease occurred in July and August during periods of hot, humid, and rainy weather. Among 52 cultivars in the 2001 trial, only 'Tropicana Pink', 'Tropicana Rose' and 'Stardust Orchid' were disease free. A Rhizoctonia sp. was consistently isolated from diseased plants and further characterized as R. solani Kühn AG-1 based on its multinucleate cells and hyphal anastomosis with several AG-1 tester isolates. On potato dextrose agar, colonies displayed morphologies with characteristics of AG-1 IA and AG-1 IB, therefore, identification to AG subgroup was not made. Mature colonies ranged from light tan to brown and produced sclerotia, individually or in clumps, at the edge of the culture dish. Pathogenicity tests were performed by placing agar blocks, taken from the margins of 7-day-old cultures, on stems of eight healthy Madagascar periwinkle plants (15 to 20 cm tall). Inoculated and noninoculated control plants were held in a dew chamber at 26°C for 3 days and then moved to a greenhouse. Leaves on all inoculated plants developed water-soaked spots that turned dark brown or black prior to death, whereas noninoculated plants remained healthy. R. solani was reisolated from inoculated plants and its cultural characteristics were similar to those of the original isolate. Web blight occurs in Louisiana on Madagascar periwinkle used as landscape bedding plants, but has not been observed on container-grown plants. Web blight caused by R. solani AG-1 was previously reported on Madagascar periwinkle from Alabama (1). R. solani AG-1 has been reported previously as causing web blight in Louisiana on rosemary (2), dianthus (4), and verbena (3). To our knowledge, this is the first report of web blight on Madagascar periwinkle (C. roseus) in Louisiana. References: (1) A. K. Hagan and J. M. Mullen. Plant Dis. 77:1169, 1993. (2) G. E. Holcomb. Plant Dis. 76:859, 1992. (3) G. E. Holcomb and D. E. Carling. Plant Dis. 84:492, 2000. (4) G. E. Holcomb and D. E. Carling. Plant Dis. 84:1344, 2000.

First Report of Occurrence of Sclerotinia Blight on Petunia in Louisiana.

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.

First Report of Leaf Blight of Dianthus chinensis Caused by Rhizoctonia solani.

Dianthus chinensis (rainbow pink) is a popular seasonal bedding plant for the Gulf Coast of the United States and is primarily grown during the fall, winter, and early spring months. In August 1999, diseased plants were observed in a Baton Rouge, LA, propagation nursery with irregularly oval, tan leaf spots 3 to 10 mm in diameter. Heavily infected leaves became blighted and were killed, but plants survived and roots, crowns, and flowers were not affected. Infected leaf samples were surface-disinfected for 1 to 3 min in 70% ethyl alcohol, blotted dry, and sections were placed on 2% acidified water agar. A fungus that was identified as Rhizoctonia solani, and belonging to anastomosis group (AG)-1 IB, was consistently isolated from infected leaves. Inoculum was prepared by blending one 7-day-old plate culture, grown on acidified potato-dextrose agar, in 100 ml distilled deionized water. Pathogenicity tests were performed by dripping inoculum from a 10-ml pipette on leaf surfaces of healthy rainbow pink plants. Inoculated and noninoculated plants were held in a dew chamber at 26°C for 2 to 3 days and then removed to a greenhouse where temperatures ranged from 25 to 32°C. Inoculated plants developed water-soaked spots after 2 to 3 days that turned tan and became necrotic 5 to 10 days later. These symptoms were like those observed on the original diseased plants. R. solani was reisolated from inoculated plants, and noninoculated plants remained healthy. Although R. solani has been reported previously as a root and stem pathogen of D. chinensis (1), this is the first report of leaf blight disease caused by this fungus. Reference: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.

First Report of Oidium sp. Powdery Mildew and Tomato spotted wilt virus on Melampodium divaricatum.

Melampodium divaricatum (Rich. ex Pers.) DC. (=M. paludosum H.B.K.), a member of the family Asteraceae and native to South America, is a recent introduction for use as a summer bedding ornamental. In September 1999, melampodium plants in multiple Baton Rouge landscapes were observed with signs of powdery mildew and symptoms of a virus-like disease. Powdery mildew spread throughout one of the plantings by late November and infected flowers and leaves. An Oidium species sporulated on both leaf surfaces but was more common on the adaxial surface. Ellipsoid conidia were produced in chains, lacked fibrosin bodies, and averaged 31 × 19 µm. No sexual stage was observed. Eight of 63 plants (cv. Derby) in one of the plantings showed virus disease symptoms that included severe leaf mosaic, leaf malformation, and stunting. Leaves from infected plants were used to sap inoculate seedling plants of melampodium and Nicotiana benthamiana. Melampodium seedlings developed typical mosaic symptoms after 48 to 56 days. N. benthamiana developed severe chlorosis and mosaic, then wilted and died after 14 days. Noninoculated plants of both species remained healthy. The virus in both plant species was identified as Tomato spotted wilt virus (TSWV) by enzyme-linked immunosorbent assay (ELISA) (Agdia, Elkhart, IN). ELISA tests for presence of Impatiens necrotic spot virus were negative. This is the first report of powdery mildew and TSWV on M. divaricatum.

First Report of Downy Mildew Caused by Peronospora lamii on Salvia splendens and Salvia coccinea.

Angular chlorotic spots were observed on adaxial leaf surfaces of Salvia splendens (scarlet sage cvs. Empire Purple, Empire White, Red Pillar, and Red Hot Sally) and S. coccinea (scarlet or Texas sage cv. Lady in Red) in early May in Baton Rouge area nurseries. Leaf spots sometimes became necrotic and resulted in leaf drop. Abaxial leaf surfaces contained scattered patches of white mycelia with brown spores. Microscopic examination of mycelia revealed irregular dichotomously branched conidiophores with pointed tips and brown oval conidia. Conidiophores averaged 485 × 9 µm and conidia averaged 21 × 18 µm (16 to 26 × 15 to 23 µm) in dimensions. The fungus was identified as Peronospora lamii A. Braun (= P. swinglei Ellis & Everh.) based on these characters and its known occurrence on Salvia spp. and five other genera in the family Lamiaceae (2). Pathogenicity tests were performed by washing conidia from infected leaves into distilled water and mistinoculating S. coccinea cv. Lady in Red and S. splendens cv. Empire Purple with 50,000 spores/ml. Plants were held in a dew chamber at 20°C for 3 days, then moved to a greenhouse where temperatures ranged from 18 to 32°C. Typical angular chlorotic leaf spots developed on inoculated plants within 6 to 8 days and noninoculated plants remained healthy. The fungus did not sporulate under these greenhouse temperatures, but infected leaves that were removed and placed in a moist chamber at 25°C produced conidiophores and brown conidia typical of P. lamii within 2 to 3 days. P. lamii has been reported previously on S. officinalis (3) and S. reflexa (1) in the United States. This is the first report of downy mildew on S. coccinea and S. splendens. Appearance of the disease in retail nurseries that obtained plants from out of state (Arkansas) suggests a widespread occurrence of the disease on these host plants. References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (2) S. M. Francis. 1981. Peronospora lamii. Descriptions of Pathogenic Fungi and Bacteria No. 688. Commonwealth Mycological Institute, Kew, England. (3) R. T. McMillan and W. R. Graves. Plant Dis. 78:317, 1994.

First Report of Web Blight on Verbena Caused by Rhizoctonia solani.

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.

First Report of Sclerotium rolfsii on Catharanthus roseus.

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.

First Report of Powdery Mildew Caused by an Oidium sp. on Torenia fournieri.

Torenia fournieri Lind. ex Fourn. (wishbone flower, bluewings) is a popular summer bedding plant in Louisiana. Clown Mixture cultivars are available in garden centers in March and April. Transplants of cultivar Clown Rose were purchased, transplanted to larger pots, and maintained in a greenhouse. A powdery mildew was observed on these plants in March and all plants (six) were severely diseased by May. Symptoms included leaf distortion and yellowing. Powdery mildew was not present on transplants and none was found in later checks of garden centers. An Oidium sp. was observed sporulating on both leaf surfaces of infected plants. Conidia were ellipsoid, produced in chains, lacked fibrosin bodies, and averaged 41 × 22 µm in dimensions. No sexual stage was observed. Healthy plants of Clown Mixture cultivars were obtained and inoculated by brushing conidia from infected plant leaves to leaves of healthy plants. Plants were maintained in a greenhouse where temperatures ranged from 16 to 26°C. Hyphal growth appeared on inoculated plants after 5 days and the reproductive structures formed later appeared the same as those on originally infected plants. Uninoculated plants remained healthy. No previous reports of powdery mildew diseases of T. fournieri in the United States were found. Other powdery mildew pathogens reported on T. fournieri are Sphaerotheca fuliginea (Schlechtend.:Fr.) Pollacci in Finland and Japan and an Erysiphe sp. in Japan (1). Reference: (1) K. Amano. Host Range and Geographical Distribution of the Powdery Mildew Fungi. Japan Scientific Press, Tokyo, 1986.

First Report on Natural Occurrence of Tomato Spotted Wilt Tospovirus in Basil (Ocimum basilicum).

Virus-like symptoms were observed on basil plants (Ocimum basilicum L. 'Mrs. Burns Lemon' [MBL]) growing in containers and a demonstration plot at the Louisiana State University Burden Research Plantation, Baton Rouge, during July 1998. Symptoms consisted of ring spots, leaf distortion, and severe mosaic. Mechanical transmission of the suspect virus by sap inoculation from infected MBL to basil cvs. MBL, Aussie Sweet, Cinnamon, Siam Queen, and Sweet Dani was successful. Symptoms were similar to those on infected MBL. Nicotiana benthamiana Domin. reacted with local chlorotic spots followed by severe yellows, necrosis, and death. Electron microscopy of thin sections of infected basil revealed virus inclusions but no virus particles. However, infected N. benthamiana revealed the presence of 82-nm membrane-bound particles in the cytoplasm. The virus was identified from basil and N. benthamiana as the common strain of tomato spotted wilt tospovirus (TSWV) by enzyme-linked immunosorbent assay (Agdia, Elkhart, IN). An outbreak of thrips insects during the summer drought in 1998 was probably responsible for the occurrence of TSWV in basil. This is the first report of the occurrence of TSWV in basil (1). Reference: (1) A. A. Brunt et al., eds. 1996. Plant Viruses Online: Descriptions and Lists from the VIDE Database. Published online by Australian National University, Canberra.

First Report of Powdery Mildew Caused by an Oidium sp. on Banana Shrub (Michelia figo).

Banana shrub (Michelia figo (Lour.) Spreng.) is an evergreen grown in southern landscapes in hardiness zones 7 to 9. A powdery mildew disease has been observed sporadically on this plant for several years in the Baton Rouge area during fall months, but symptoms were always mild. During the summer and fall of 1998, banana shrub plants were observed with moderately severe powdery mildew infections that resulted in leaf chlorosis, distortion, and some defoliation. An Oidium sp. was present on both leaf surfaces, but sporulation was more abundant on the abaxial surfaces. Conidia were ellipsoid, produced in chains, devoid of conspicuous fibrosin bodies, and averaged 37 × 19 µm. No sexual stage was found. Conidia brushed from infected leaves to healthy leaves of a potted banana shrub maintained in a greenhouse caused new infections in 5 to 8 days. Factors responsible for the increased severity of the disease in 1998 are unknown, but the unusually dry summer may have contributed to the increased incidence of this disease. An Oidium sp. was listed on M. figo in Australia and the United States (1), but no other reports were found to confirm this. This is the first report of the occurrence of a powdery mildew on M. figo in the United States. Reference: (1) K. Amano. Host Range and Geographical Distribution of the Powdery Mildew Fungi. Japan Scientific Press, Tokyo, 1986.

First Report of Basil Leaf Spot Caused by Pseudomonas cichorii in Louisiana and Cultivar Screening Results.

A leaf spot of basil, Ocimum basilicum L., was observed on container-grown and field plantings of cultivars Aussie Sweet and Sweet Basil. The disease was of minor importance under field conditions, but was of potential economic importance in seedling production. Gray to black, watersoaked, necrotic spots commonly developed at leaf margins. Large numbers of bacteria were released from cut lesions when viewed by light microscopy. Single colony bacterial isolates were established on nutrient dextrose agar (NDA) and yeast extract-dextrose-calcium carbonate agar (YDC). Pathogencity tests were performed by misting a water suspension containing 104 bacterial cells per ml on healthy basil plants. Plants were held for 24 h in a dew chamber at 26°C and then moved to a greenhouse for observation. Typical leaf spots developed on inoculated plants in 2 days, but not on healthy control plants, and the bacterium was reisolated. The bacterium was characterized as a gram-negative, motile rod, negative for potato rot test, positive in tobacco hypersensitivity test, and oxidase positive. Isolates were identified as Pseudomonas cichorii according to the Biolog Microplate system (similarities ranged from 0.937 to 0.995). Screening tests were conducted by inoculating 15 basil cultivars, six replicates each, and rating them for disease severity based on a scale of 1 to 5 in which 1 = no disease and 5 = dead plants. Cultivars most resistant to bacterial leaf spot (ratings in parentheses are averages of two tests and those followed by the same letter are not significantly different according to Tukey's Studentized Range Test, P = 0.05) were Green Bouquet (2.0 a), Piccolo (2.2 a), Mrs. Burn's Lemon (2.2 a), Genovese (2.4 a), and Dark Opal (2.5 ab). Moderately susceptible cultivars were Bush Green (2.8 abc), Sweet Basil (2.8 abc), Large Green (2.9 abcd), Lemon (3.1 abcd), and Mexican Spice (3.6 bcd). The most susceptible cultivars were Lettuce Leaved (3.8 cd), Thai (3.8 cd), Napoletano (4.0 de), Green Ruffles (5.0 e), and Purple Ruffles (5.0 e). Bacterial leaf spot of basil caused by P. cichorii was first reported in the U.S. from Florida (1). Other bacterial diseases reported on basil include leaf blight from Egypt caused by P. syringae (2) and leaf necrosis from California caused by P. viridiflava (3). This is the first report on the occurrence of basil bacterial leaf spot in Louisiana and the first reported information on cultivar susceptibility. References: (1) S. M. Burgess et al. Proc. Fla. State Hortic. Soc. 99:249, 1986. (2) S. A. M. El-Sadek et al. Assiut J. Agric. Sci. 22:2, 1991. (3) E. L. Little et al. Plant Dis. 78:831, 1994.

First Report of Anthracnose of Velvet Ash Caused by Discula fraxinea in Louisiana.

Velvet ash (Fraxinus velutina Torr.), a native tree of the southwestern United States, was commonly planted in Louisiana and other southeastern states until horticulturalists lost interest in the plant due to insect and disease problems. For several years, velvet ash trees in Baton Rouge have exhibited necrotic leaf spots and blotches during March and April. Trees frequently have 10 to 25% foliage infection and those most severely infected may show 50% defoliation. Small hyaline conidia that averaged 9.0 × 3.8 µm were produced in acervuli in necrotic tissue on lower leaf surfaces of affected trees. A fungus that produced similar conidia was consistently isolated from infected leaves and grown on potato dextrose agar. Pathogenicity tests were performed by misting 3 × 106 conidia per ml on leaf surfaces of velvet ash seedlings that were then placed in a dew chamber maintained at 26°C for 48 h. Chlorotic leaf spots developed on inoculated plants in 4 to 6 days at 24°C and were followed by necrotic spots and blotches 4 days later. The fungus was reisolated and identified as Discula fraxinea (Peck) Redlin & Stack (previously known as Gloeosporium aridum Ellis & Holw.) (2). Velvet ash anthracnose was first reported from California in 1949 (1), but this is the first report of its occurrence in Louisiana. References: (1) D. M. Coe and W. W. Wagener. Plant Dis. Rep. 33:232, 1949. (2) S. C. Redlin and R. W. Stack. Mycotaxon 32:175, 1988.

First Report of Fire Blight on Indian Hawthorn Cultivar Olivia in Louisiana.

Twig and branch death were observed on Indian hawthorn (Raphiolepis indica (L.) Lindl.) cv. Olivia in an experimental planting in May 1998. Symptoms resembled those of fire blight caused by Erwinia amylovora and included the release of large numbers of bacteria from stem sections placed in water drops. Small pieces of wood from surface-disinfected cv. Olivia twigs were crushed in drops of sterile water, dilutions made and streaked on yeast extract-dextrose-CaCO3 agar, and single colony cultures established. Pathogenicity tests were performed on immature pear (Pyrus communis L. 'Kieffer') and cherry laurel (Prunus caroliniana (Mill.) Aiton) fruits by injecting them with bacterial suspensions containing 105 CFU/ml. Twigs of cv. Olivia were inoculated with a needle that had been dipped in the bacterial cultures. Control inoculations were done with sterile water. Inoculated fruits (nine pear and eight cherry laurel) turned black and oozed bacteria after 5 to 10 days and seven of nine inoculated twigs developed leaf chlorosis followed by browning and death of foliage and twigs after 7 days. Control inoculations were negative. The bacterium was reisolated and identified as E. amylovora based on positive pathogenicity tests and results from Biolog Microplate tests. Although R. umbellata (Thunb.) Makino is a natural host of E. amylovora (1), R. indica was reported only as an experimental host (2) but is now generally recognized as a natural host of E. amylovora. Among nine Indian hawthorn cultivars. (total of 48 plants) in the Louisiana planting, only cv. Olivia was infected with fire blight and all six plants died by late summer. References: (1) E. M. Hildebrand. Phytopathology 44:192, 1954. (2) H. E. Thomas and H. E. Thomas. Phytopathology 21:425, 1931.