scholarly journals First Report of Powdery Mildew Caused by Podosphaera (Sphaerotheca) fusca on Euryops pectinatus in North America

Plant Disease ◽  
2000 ◽  
Vol 84 (9) ◽  
pp. 1048-1048 ◽  
Author(s):  
G. S. Saenz ◽  
S. T. Koike ◽  
N. Shishkoff
Keyword(s):  
United States ◽  
New York ◽  
North America ◽  
Powdery Mildew ◽  
Fungal Growth ◽  
The United States ◽  
Voucher Specimen ◽  
First Report ◽  
Humidity Chamber ◽  
Powdery Mildew Pathogen

Gray-leaved Euryops (Euryops pectinatus Cass., Asteraceae) is an evergreen shrub that is widely planted in landscapes in the United States. In the fall of 1999, powdery mildew was observed on E. pectinatus planted in landscapes in Redlands (San Bernardino County), CA. Symptoms consisted only of slight cupping of leaves. Fungal growth was observed on stems, leaves, petioles, and pedicels and was ectophytic and amphigenous. The white mycelium was patchy to effuse. Hyphal appressoria were indistinct (1). Conidiophore foot cells were cylindric and sometimes were tapered toward or constricted at the base. Foot cells measured 30 to 50 by 10 to 12 μm and were followed by one to two shorter cells. Conidia were cylindric to slightly doliform, borne in chains of two to three, and measured 26 to 38 by 14 to 18 μm. Conidial length to width ratios ranged from 1.7 to 2.4. Catenate conidia had crenate edge lines (3). Conidia possessed conspicuous fibrosin bodies and from their sides produced short germ tubes without appressoria. Cleistothecia were not observed. Based on these characters, the fungus was identified as Podosphaera fusca (Fr.) U. Braun & N. Shishkoff (Podosphaera sect. Sphaerotheca) (1,2). Pathogenicity was confirmed by gently pressing diseased leaves onto leaves of healthy E. pectinatus plants. Plants were incubated in a humidity chamber at 22 to 24°C and after 12 to 14 days powdery mildew colonies developed. E. pectinatus cv. Viridis, a cultivar that lacks the extensive pubescence of E. pectinatus, also developed disease when inoculated. This appears to be the first report of powdery mildew on E. pectinatus in North America. A voucher specimen has been deposited into the University of California Herbarium (accession # UC1738635). P. fusca was also observed on cv. Viridis in a nursery in New York in 1999. It is unclear where this pathogen originated. P. fusca parasitizes a large number of asteraceous species including dandelion (Taraxacum officinalis) and sowthistle (Sonchus spp.) weeds, which occur in the area and sometimes are infected with powdery mildew. The Euryops powdery mildew pathogen may be a race that is different than those found on other composites in the United States. The fungus was observed on plants in shaded areas but not on plants in full sun. References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (3) H. D. Shin and Y. J. La. Mycotaxon 46:445, 1993.

scholarly journals First Report of Powdery Mildew on Nandina domestica (Berberidaceae) in North America

Plant Disease ◽  
2000 ◽  
Vol 84 (6) ◽  
pp. 705-705 ◽  
Author(s):  
G. S. Saenz ◽  
S. T. Koike ◽  
H. J. Scheck
Keyword(s):  
North America ◽  
Powdery Mildew ◽  
Santa Barbara ◽  
Voucher Specimen ◽  
First Report ◽  
The United Kingdom ◽  
Humidity Chamber ◽  
Powdery Mildew Pathogen ◽  
The University ◽  
Germ Tubes

Nandina domestica Thunb. (heavenly bamboo) is an ornamental plant that is widely planted in landscapes in California and other states. Since 1996, powdery mildew disease has been seen on outdoor landscape N. domestica in various regions of California (Alameda, Monterey, Riverside, and Santa Barbara counties). Symptoms consist of reddening of leaf and stem tissues colonized by the fungus and curling and twisting of infected leaves. The following observations were the same for all collected isolates. White ectophytic mycelium was observed on leaves and petioles. Mycelium on leaves was amphigenous, mostly epiphyllous, and effused or in patches. Hyphal appressoria were nipple-shaped to lobed and sometimes opposite in orientation. Conidiophores were cylindrical, straight, sometimes slightly flexuous, 22 to 32 × 6 to 8 μm in dimension, and followed by one to two shorter cells. Conidia were cylindrical, produced singly, and 27 to 42 × 11.5 to 14 μm in dimension. Fibrosin bodies were not observed. Conidial germ tubes were approximately twice the length of the spore, originated from the ends of the spore, and terminated in simple appressoria. Cleistothecia were not present. Based on these characteristics, the fungus was identified as Microsphaera berberidis (DC) Lév. (1). Pathogenicity was confirmed by gently pressing diseased leaves on leaves of healthy N. domestica plants. Plants were incubated in a humidity chamber at 22 to 24°C, and after 10 to 14 days, powdery mildew colonies developed. A voucher specimen was deposited in the University of California Herbarium (UC 1738622). Additional inoculation experiments showed that four other N. domestica cultivars were susceptible (Compacta Nana, Gulf Stream, Harbour Dwarf, and Royal Princess). Helfer (2) noted several possible candidates for the Nandina powdery mildew pathogen in the United Kingdom. However, due to the conidial characteristics of that fungus and the paucity of character descriptions for the several species mentioned, no species name was given to the Edinburgh isolate. In contrast, the mitosporic characteristics of our isolates fit the description for M. berberidis. This is the first report of powdery mildew on N. domestica in North America. References: (1) U. Braun. Nova Hedwigia 89:1, 1987. (2) S. Helfer. Plant Dis. 79:424, 1995.

scholarly journals Sawadaea tulasnei Powdery Mildew of Norway Maple (Acer platanoides) in North America

Plant Disease ◽  
2006 ◽  
Vol 90 (6) ◽  
pp. 830-830
Author(s):  
J. Weiland ◽  
G. Stanosz
Keyword(s):  
United States ◽  
New York ◽  
North America ◽  
Powdery Mildew ◽  
Acer Saccharum ◽  
The United States ◽  
Rdna Its ◽  
Maple Leaves ◽  
Norway Maple ◽  
Genus 2

Norway maple leaves bearing powdery mildew were collected from one location in the fall of 2003 and four locations (as much as 1.5 km apart) in the fall of 2005 in Buffalo, NY. No powdery mildew was observed on leaves collected from sugar maples (Acer saccharum) that were present in the vicinity of affected Norway maples at two locations. Trees were located along streets and in yards. Diseased leaves were present throughout tree crowns but lower leaves were more commonly affected. White mycelium was present in irregular, discrete, scattered spots only on the upper surface of leaves and on both sides of wings of samaras. Typically, <10% of the upper leaf area bore visible mycelium. Cleistothecia were present singly or in groups on the mycelium. Morphology of cleistothecia on leaves collected each year, including simple and bifid appendages with uncinate to circinate apices, was sufficient to identify the pathogen to the genus Sawadaea (1). Other characteristics were not sufficiently distinct to make an identification of S. bicornis or S. tulasnei (1), each a European species found on Acer spp. However, a sample from 2003 was supplied by the authors for use in a study of phylogeny of the genus (2) that served as a first report of the species in the United States. Analysis of nuclear rDNA ITS sequence of this specimen (GenBank Accession No. AB193390) placed the sample in a clade with S. tulasnei specimens from Europe. In the same study, powdery mildew samples from Acer spp. in Ohio and Montreal, Canada also were placed in this clade. Thus, occurrence of S. tulasnei in North America is confirmed. S. bicornis was recently identified (based on morphology) on Norway maple in the western United States (3). Specimens from Buffalo, NY have been deposited in the U.S. National Fungus Collections (BPI 871210). References: (1) U. Braun. The Powdery Mildews (Erysiphales) of Europe. Gustav Fischer Verlag, Jena-Stuttgart-New York, 1995. (2) S. Hirose et al. Mycol. Res. 109:912, 2005. (3) C. Nischwitz and G. Newcombe. Plant Dis. 87:451, 2003.

scholarly journals First Report of Leaf Spot Caused by Cercospora bizzozeriana on Lepidium draba in the United States

Plant Disease ◽  
2009 ◽  
Vol 93 (1) ◽  
pp. 108-108 ◽  
Author(s):  
A. J. Caesar ◽  
R. T. Lartey ◽  
D. K. Berner ◽  
T. Souissi
Keyword(s):  
United States ◽  
North America ◽  
Sugar Beet ◽  
Leaf Spot ◽  
The United States ◽  
Initial Report ◽  
Voucher Specimen ◽  
First Report ◽  
Leaf Spots ◽  
Lepidium Draba

The herbaceous perennial Lepidium draba L. is an invasive weed of rangelands and riparian areas in North America and Australia. As of 2002, it had infested 40,500 ha of rangeland in Oregon and large areas in Wyoming and Utah. Little is known of plant pathogens occurring on L. draba, especially in the United States, that could be useful for biological control of the weed. Leaf spots were first noted on a stand of L. draba near Shepherd, MT in 1997. The spots were mostly circular but sometimes irregularly shaped and whitish to pale yellow. The pathogen was erroneously assumed to be Cercospora beticola since its morphological traits closely resembled that species and the area had large fields of sugar beet with heavy Cercospora leaf spot incidence. Diseased leaves of L. draba were collected in 1997 and 2007. Conidia, borne singly on dark gray, unbranched conidiophores produced on dark stromata late in the season, were elongate, hyaline, multiseptate, 38 to 120 × 2 to 6 μm (mostly 38 to 50 × 2 to 5 μm) and had bluntly rounded tips and wider, truncate bases. These characteristics were consistent with the description of C. bizzozeriana Saccardo & Berlese (2). To isolate the fungus, spores were picked from fascicles of conidiophores with a fine-tipped glass rod, suspended in sterile water, and spread on plates of water agar. Germinated spores were transferred to potato dextrose agar (PDA). The ITS1, 5.8S, and ITS2 sequences of this fungus (GenBank Accession No. EU887131) were identical to sequences of an isolate of C. bizzozeriana from Tunisia (GenBank Accession No. DQ370428). However, these sequences were also identical to those of a number of Cercospora spp. in GenBank, including C. beticola. We also compared the actin gene sequences of the Montana isolate of C. bizzozeriana (GenBank Accession No. FJ205397) and an isolate of C. beticola from Montana (GenBank Accession No. AF443281); the sequences were 94.6% similar, an appreciable difference. For pathogenicity tests, cultures were grown on carrot leaf decoction agar. Aqueous suspensions of 104 spores per ml from cultures were sprayed on 6-week-old L. draba plants. Plants were covered with plastic bags and placed on the greenhouse bench at 20 to 25°C for 96 h. Koch's postulates were completed by reisolating the fungus from the circular leaf spots that appeared within 10 days, usually on lower leaves. Spores of C. bizzozeriana were also sprayed on seedlings of sugar beet, collard, mustard, radish, cabbage, and kale under conditions identical to those above. No symptoms occurred. After the discovery of the disease in 1997, plants of L. draba in eastern Montana, Wyoming, and Utah were surveyed from 1998 to 2003 for similar symptoms and signs, but none were found. This, to our knowledge, is the first report of C. bizzozeriana in the United States. The initial report of the fungus in North America was from Manitoba in 1938 (1). It has recently been reported as occurring on L. draba in Tunisia (4) and Russia (3) and is reported as common in Europe (2). A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI No. 878750A). References: (1) G. R. Bisby. The Fungi of Manitoba and Saskatchewan. Natl. Res. Council of Canada, Ottawa, 1938. (2) C. Chupp. A Monograph of the Fungus Genus Cercospora. C. Chupp, Ithaca, NY, 1953. (3) Z. Mukhina et al. Plant Dis. 92:316, 2008. (4) T. Souissi et al. Plant Dis. 89:206, 2005.

scholarly journals First Report of Powdery Mildew Caused by Podosphaera xanthii on Sechium edule in the United States

Plant Disease ◽  
2009 ◽  
Vol 93 (12) ◽  
pp. 1348-1348 ◽  
Author(s):  
R. Singh ◽  
D. M. Ferrin ◽  
M. C. Aime
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
New Orleans ◽  
Dna Analysis ◽  
The United States ◽  
Abaxial Surface ◽  
Internal Transcribed Spacer Region ◽  
Voucher Specimen ◽  
First Report ◽  
Sechium Edule

Sechium edule (Jacq.) Sw., also known as mirliton or chayote, is a perennial, monoecious, cucurbitaceous plant native to Mexico and Central America. It is cultivated worldwide for a variety of uses (4). Mirliton fruit is rich in carbohydrates, has 16 amino acids, and is a traditional staple in New Orleans, LA. During the spring of 2009, the LSU AgCenter's Plant Disease Diagnostic Clinic received diseased mirliton plants from a small commercial grower in New Orleans. Symptoms included yellow, irregular spots on both surfaces of the leaves. Microscopic examination revealed the presence of powdery mildew conidia and conidiophores. Initially, white, cottony mycelial colonies were present on the abaxial surface, but as the disease progressed, white, cottony colonies developed on the adaxial surface, the spots coalesced, and the entire leaf turned yellow and necrotic. Conidia were hyaline, ovoid, borne in long chains with crenate edges, and measured 25.6 to 36.6 μm long (mean = 31.2) × 14.6 to 18.3 μm wide (mean = 17.1). Conidia contained fibrosin bodies and produced a lateral germ tube with a simple appressorium. Conidiophores were erect, simple, unbranched, and measured 54.9 to 76.9 μm long (mean = 66.4) × 11.0 to 14.6 μm wide (mean = 12.9). The cylindrical foot cell had a simple base with basal septum adjacent to the mycelium. No teleomorph was observed. Morphologically, this powdery mildew fits either Podosphaera fusca or P. xanthii so DNA analysis was conducted. We designed Podosphaera-specific primers PFITS-F (5′-CCAACTCGTGCTGTGAGTGT-3′) and PF5.8-R (5′-TGTTGGTTTCTTTTCCTCCG-3′) to amplify and sequence the internal transcribed spacer region (ITS) of the nuclear rDNA. The 331-bp sequence (GenBank Accession No. GQ902939) was identical with haplotype 27 of P. fusca (GenBank Accession No. AB040324) (3), which is now called P. xanthii (1). Pathogenicity tests were conducted by pressing infected leaves against healthy leaves of two vines. A noninoculated vine served as a control. Plants were maintained in a greenhouse at 30°C. Five days after inoculation, yellow, irregular spots appeared on the inoculated vines and white, powdery mildew colonies appeared on the abaxial surface. Spots coalesced and the entire leaf turned yellow 8 days after inoculation and necrotic 12 days after inoculation. No symptoms developed on the controls. On the basis of DNA sequence data, this powdery mildew is identified as P. xanthii sensu (1). Erysiphe cichoracearum has been previously reported to cause powdery mildew on mirlitons in Florida and Hawaii (2). To our knowledge, this is the first report of powdery mildew caused by P. xanthii on mirliton in the United States. A voucher specimen has been deposited in the Bernard Lowy Mycological Herbarium (LSUM 185359). References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:31, 2000. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, SMML, Online publication. USDA-ARS, 2009. (3) T. Hirata et al. Can. J. Bot. 78:1521, 2000. (4) M. Janssens et al. Tropical Crops. ARTS; Field and Vegetable Crops, PTS 130. Bonn, Germany, 2002/03.

scholarly journals First Report of Impatiens Downy Mildew Outbreaks Caused by Plasmopara obducens Throughout the Hawai'ian Islands

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 696-696 ◽  
Author(s):  
J. A. Crouch ◽  
M. P. Ko ◽  
J. M. McKemy
Keyword(s):  
United States ◽  
Downy Mildew ◽  
The United States ◽  
Molecular Data ◽  
Economic Losses ◽  
Voucher Specimen ◽  
First Report ◽  
Plastic Bags ◽  
Leaf Surfaces ◽  
Impatiens Walleriana

Downy mildew of impatiens (Impatiens walleriana Hook.f.) was first reported from the continental United States in 2004. In 2011 to 2012, severe and widespread outbreaks were documented across the United States mainland, resulting in considerable economic losses. On May 5, 2013, downy mildew disease symptoms were observed from I. walleriana ‘Super Elfin’ at a retail nursery in Mililani, on the Hawai'ian island of Oahu. Throughout May and June 2013, additional sightings of the disease were documented from the islands of Oahu, Kauai, Maui, and Hawai'i from nurseries, home gardens, and botanical park and landscape plantings. Symptoms of infected plants initially showed downward leaf curl, followed by a stippled chlorotic appearance on the adaxial leaf surfaces. Abaxial leaf surfaces were covered with a layer of white mycelia. Affected plants exhibited defoliation, flower drop, and stem rot as the disease progressed. Based on morphological and molecular data, the organism was identified as Plasmopara obducens (J. Schröt.) J. Schröt. Microscopic observation disclosed coenocytic mycelium and hyaline, thin-walled, tree-like (monopodial branches), straight, 94.0 to 300.0 × 3.2 to 10.8 μm sporangiophores. Ovoid, hyaline sporangia measuring 11.0 to 14.6 × 12.2 to 16.2 (average 13.2 × 14.7) μm were borne on sterigma tips of rigid branchlets (8.0 to 15.0 μm) at right angle to the main axis of the sporangiophores (1,3). Molecular identification of the pathogen was conducted by removing hyphae from the surface of three heavily infected leaves using sterile tweezers, then extracting DNA using the QIAGEN Plant DNA kit (QIAGEN, Gaithersburg, MD). The nuclear rDNA internal transcribed spacer was sequenced from each of the three samples bidirectionally from Illustra EXOStar (GE Healthcare, Piscataway, NJ) purified amplicon generated from primers ITS1-O and LR-0R (4). Resultant sequences (GenBank KF366378 to 80) shared 99 to 100% nucleotide identity with P. obducens accession DQ665666 (4). A voucher specimen (BPI892676) was deposited in the U.S. National Fungus Collections, Beltsville, MD. Pathogenicity tests were performed by spraying 6-week-old impatiens plants (I. walleriana var. Super Elfin) grown singly in 4-inch pots with a suspension of 1 × 104 P. obducens sporangia/ml until runoff using a handheld atomizer. Control plants were sprayed with distilled water. The plants were kept in high humidity by covering with black plastic bags for 48 h at 20°C, and then maintained in the greenhouse (night/day temperature of 20/24°C). The first symptoms (downward curling and chlorotic stippling of leaves) and sporulation of the pathogen on under-leaf surfaces of the inoculated plants appeared at 10 days and 21 days after inoculation, respectively. Control plants remained healthy. Morphological features and measurements matched those of the original inoculum, thus fulfilling Koch's postulates. To our knowledge, this is the first report of downy mildew on I. walleriana in Hawai'i (2). The disease appears to be widespread throughout the islands and is likely to cause considerable losses in Hawai'ian landscapes and production settings. References: (1) O. Constantinescu. Mycologia 83:473, 1991. (2) D. F. Farr and A. Y. Rossman. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ July 16, 2013. (3) P. A. Saccardo. Syllogue Fungorum 7:242, 1888. (4) M. Thines. Fungal Genet Biol 44:199, 2007.

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 First Occurrence of Downy Mildew of Statice, Caused by Peronospora statices, in California and the Rest of the United States

Plant Disease ◽  
1998 ◽  
Vol 82 (5) ◽  
pp. 591-591 ◽  
Author(s):  
S. T. Koike ◽  
P. A. Nolan ◽  
S. A. Tjosvold ◽  
K. L. Robb
Keyword(s):  
United States ◽  
Downy Mildew ◽  
Fungal Growth ◽  
The United States ◽  
San Diego County ◽  
Leaf Spots ◽  
Initial Symptoms ◽  
First Occurrence ◽  
Humidity Chamber ◽  
Favorable Conditions

In California, hybrid statice (Misty series; Limonium bellidifolium × Limonium latifolium) is grown as a commercial cutflower crop in fields and greenhouses. In 1997, downy mildew was observed on statice plantings in both southern (San Diego County) and central (Monterey and Santa Cruz counties) parts of coastal California. Initial symptoms consisted of light green, irregularly shaped leaf spots that, after a few days, became chlorotic. As disease progressed, chlorotic spots coalesced and turned necrotic, at times resulting in extensive death of leaf tissues. Under favorable conditions, the purple to gray sporulation of the pathogen could be seen on abaxial surfaces of leaves. Conidiophores had main trunks with dichotomous branches and measured 194 to 335 μm in length (mean = 229 μm) from the base to the first branches and 7 to 8 μm across at the widest part. Branch ends were slender with curved tips that measured 5 to 8 μm long. Conidia were ovoid to globose with very short pedicels, and measured 14 to 19 μm × 14 to 17 μm. Conidial surfaces appeared slightly roughened when viewed with a scanning electron microscope. Clearing leaf sections with 10% NaOH (1) revealed the presence of yellow-brown, globose oospores that measured 31 to 47 μm. The pathogen was identified as Peronospora statices (1). Pathogenicity was demonstrated by pressing leaves with abundant sporulation against healthy leaves of test plants (Misty White) and then placing inoculated plants in a humidity chamber. After 10 to 12 days, symptoms similar to those originally observed developed on inoculated plants; after 14 to 16 days, purple fungal growth morphologically similar to the original isolates grew on leaves. Uninoculated control plants did not develop symptoms or signs of downy mildew. This is the first report of downy mildew caused by P. statices on statice in California and the rest of the United States. The disease has also been confirmed on Blue Fantasia (L. bellidifolium × L. perezii). This disease has been reported previously in Italy, The Netherlands, and the United Kingdom (1). Reference: (1) G. S. Hall et al. Eur. J. Plant Pathol. 103:471, 1997.

scholarly journals First Report of Subanguina radicicola, the Root-Gall Nematode Infecting Poa annua Putting Greens in Washington State

Plant Disease ◽  
2007 ◽  
Vol 91 (7) ◽  
pp. 905-905 ◽  
Author(s):  
N. A. Mitkowski
Keyword(s):  
United States ◽  
New York ◽  
The United States ◽  
Washington State ◽  
Poa Annua ◽  
Golf Course ◽  
Severe Damage ◽  
Surrounding Water ◽  
Putting Greens ◽  
First Report

In the fall of 2006, a golf course in Snoqualmie, WA renovated five putting greens with commercially produced Poa annua L. sod from British Columbia, Canada. Prior to the renovation, the greens had been planted with Agrostis stolonifera L. cv. Providence, which was removed during the renovation. In February of 2007, chlorotic patches were observed on the newly established P. annua greens. When the roots were examined, extensive galling was observed throughout plant roots. Galls were slender and twisted in appearance and less than one millimeter long. Upon dissection of washed galls, hundreds of eggs were exuded into the surrounding water droplet and both mature male and female nematodes were observed. Further morphometric examination of males, females, and juvenile nematodes demonstrated that they were Subanguina radicicola (Greef 1872) Paramanov 1967 (1). Amplification of nematode 18S, ITS1, and 5.8S regions, using previously published primers (2), resulted in a 100% sequence match with the publicly available sequence for S. radicicola, GenBank Accession No. AF396366. Each P. annua plant had an average of six galls (with a range of 1 to 8), primarily located within the top 2 cm of the soil. All five new P. annua putting greens at the golf course were infested with the nematode. Additionally, P. annua from two A. stolonifera cv. Providence greens that had not been renovated was infected, suggesting that the population occurred onsite and was not imported from the Canadian sod. S. radicicola has been identified as causing severe damage in New Brunswick, Canada on P. annua putting greens and in wild P. annua in the northwestern United States, but to our knowledge, this is the first report of the nematode affecting P. annua on a golf course in the United States. References: (1) E. L. Krall. Wheat and grass nematodes: Anguina, Subanguina, and related genera. Pages 721–760 in: Manual of Agricultural Nematology. Marcel Dekker, New York, 1991. (2) N. A. Mitkowski et al. Plant Dis. 86:840, 2002.

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