bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Insect Exclusion on the Incidence of Yellow Vine Disease and of the Associated Bacterium in Squash
Authors: Bextine Blake , Wayadande Astri , Bruton B. D. , Pair S. D. , Mitchell Forrest , Fletcher Jacqueline
Published: May 2007

Yellow vine (YV) of cucurbits, associated with a phloem-limited bacterium, causes rapid wilting and death in affected plants. In a previous study, experimental insecticide-treated plots had a lower incidence of YV than untreated plots, suggesting that insects were involved in the transmission of the bacterium. In the study reported here, we compared the incidence of YV and polymerase chain reaction (PCR) detection of the YV bacterium in noncovered squash plants (Cucurbita pepo var. melopepo) with plants covered with fine-mesh fabric secured in such a way that insects were excluded. Rows of squash were covered with row mesh cover that was stretched over hoops and anchored in the soil. The row cover was removed after 40 or 50 days, at which time all plants were sampled destructively by harvesting the crown and root. In the first experiment, 3% of the noncovered plants had foliar symptoms, 7% were positive with the use of Dienes' stain, and 25% were positive when analyzed by PCR with specific primers. No covered plants were positive by any detection method, and no plants in the second experiment had foliar symptoms or tested positive with Dienes' stain. However, 20% of noncovered and 0% of covered plants were PCR positive. These data support the hypothesis that insects were involved in the transmission of the bacterium.
Lack of Induced Systemic Resistance in Peanut to Late Leaf Spot Disease by Plant Growth-Promoting Rhizobacteria and Chemical Elicitors
Authors: Zhang Shouan , Reddy M. S. , Kokalis-Burelle Nancy , Wells Larry W. , Nightengale Stevan P. , Kloepper Joseph W.
Published: May 2007

A disease assay was optimized for late leaf spot disease of peanut using Cercosporidium per-sonatum in the greenhouse, and this assay was used in attempts to elicit induced systemic resistance using strains of plant growth-promoting rhizobacteria (PGPR) and chemical elicitors. Nineteen strains of spore-forming bacilli PGPR, including strains of Paenibacillus macerans, Brevibacillus brevis, Bacillus laterosporus, B. subtilis, B. pumilus, B. amyloliquefaciens, B. sphaericus, B. cereus, and B. pasteurii, which previously elicited systemic disease control activity on other crops, were evaluated in greenhouse assays. Seven PGPR strains elicited significant disease reduction in a single experiment; however, none repeated significant protection achieved in the greenhouse assay, while significant protection consistently occurred with the fungicide chlorothalonil (Bravo). In other greenhouse trials, neither stem injections of C. personatum nor foliar sprays of chemicals, including salicylic acid, sodium salicylate, isonicotinic acid, or benzo[1,2,3]thiadiazole-7-carbothioc acid S-methyl ester (Actigard), which elicit systemic acquired resistance on other crops, elicited significant disease protection. In contrast, foliar sprays with DL-β-amino-n-butyric acid (BABA), which is an elicitor of localized acquired resistance, resulted in significantly less late leaf spot disease in one of two tests. Combination treatments of four PGPR strains with BABA in the greenhouse did not significantly protect peanut from late leaf spot. Field trials conducted over two growing seasons indicated that none of the 19 PGPR strains, applied as seed treatments at two concentrations, significantly reduced late leaf spot disease. The same chemical elicitors tested in the greenhouse, including BABA, did not elicit significant disease protection. Some combinations of four PGPR and BABA significantly reduced the disease at one but not at two sample times. Collectively, these results suggest that late leaf spot resistance in peanut is not systemically inducible in the same manner as is resistance to diseases in other crops by PGPR and chemical inducers.
First Report of Garlic Rust Caused by Puccinia allii in Oregon
Authors: Griesbach J. A. , Putnam M. L. , Driesner D.
Published: May 2007

In June of 2000, garlic rust caused by Puccinia allii F. Rudolphi was detected in a single commercial garlic field (Allium sativum L.) in the Willamette Valley of western Oregon. To our knowledge, this is the first report of P. allii in Oregon. The pathogen was present in low levels throughout the majority of the garlic field with little apparent effect; however, several 10 to 20 m wide lenses of severely damaged plants were observed. In the lenses, the plants were stunted and the outer leaves were prematurely senescent. Uredia were abundant and irregularly scattered on the leaves and gave the heavily infected plants an orange cast. The field was resurveyed in August and telia and uredia were collected. Urediospores were ellipsoid and measured 29 to 35 × 20 to 26 μm. Urediospore walls were generally hyaline, 1 to 2 μm thick and echinulate. Telia were black, oval to elongate, and non-erumpent to slightly erumpent. Teliospores were predominantly two-celled and measured 40 to 62 × 19 to 30 μm. The cap cells were angular to acuminate and irregular. Pedicels were generally shorter than the length of the spore. These characteristics are consistent with published descriptions of P. allii (1). P. allii was not detected in any of the 103 garlic or 113 onion seed fields enrolled in the state's phytosanitary certification programs during 2000.

References: (1) G. F. Laundon and J. M. Waterson. CMI Descr. Pathog. Fungi Bact. No. 52, 1965.
Proof for the Occurrence of Flower Blight Caused by Ciborinia camelliae in Italy
Authors: Garibaldi A. , Gilardi G. , Bertetti D. , Gullino M. L.
Published: May 2007

Camellia cultivation has a long history in the Lake Maggiore area of Northern Italy where a wide selection of varieties is present. In March to April 2001, a previously unconfirmed flower blight was observed on a collection of camellia varieties grown in a garden. Initial symptoms included the appearance of irregular, small, brown spots on the petals. Under favorable temperature and moisture conditions, the lesions enlarged rapidly and coalesced to form large spots that turned the entire petal brown. When the infection reached the base of the petal, it spread to other petals of the flower and finally caused the entire flower to show symptoms of blight. Eventually, the whole flower became uniformly dull brown and dropped from the plant. At the bases of infected flowers, a white or gray ring of mycelium was seen when the calyx was removed. Fungal pseudoparenchyma in the base of the petals eventually formed sclerotia and microconidia. Large numbers of apothecia and sclerotia were frequently in the soil, below infected plants. Apothecia were nearly sessile or, when buried in soil, had stipes up to 40 mm in length. They also had saucer-like disks of 5 to 20 mm in diameter. Ciborinia camelliae was recovered consistently from infected petals, sclerotia, and spores collected from apothecia, then plated on potato dextrose agar amended with 100 mg of streptomycin sulfate per liter. Pathogenicity of three isolates was confirmed by inoculating flowers of potted camellia plants (cv. Waterhouse), with spores obtained from apothecia. Noninoculated plants served as controls. All plants were kept in a growth chamber at 20°C and kept moist. Inoculated plants developed symptoms within 12 days, whereas control plants remained symptomless. C. camelliae was reisolated from flowers of inoculated plants. Camellia flower blight was first observed in Japan, in 1919, then in the United States (1938), New Zealand (1993), and more recently in several European countries, including Italy (1999) (1). This report confirms the occurrence of camellia flower blight in Italy and apparently is the first report in which C. camelliae was isolated and pathogenicity tests completed.

Reference: (1) C. H. Taylor and P. G. Long, NZ J. Crop Hortic. Sci. 28:123, 2000.
The Roles of Three Fungicides in the Epidemiology of Potato Late Blight
Authors: Mayton H. , Forbes G. A. , Mizubuti E. S. G. , Fry W. E.
Published: May 2007

Three fungicides were tested in the field for efficacy on late blight caused by Phytophthora infestans. The effects of these fungicides on epidemic development, lesion growth rate and sporulation were measured. No fungicide completely arrested epidemic development under the environmental conditions of these experiments. However, the fungicide mixture, propamocarb hydrochloride plus chlorothalonil, had the most suppressive effect of the fungicides tested. The mechanism of effect included suppression of disease progress and lesion expansion. Growth chamber studies demonstrated that 24°C compared to 10 or 16°C limited cymoxanil efficacy.
First Report of Potato spindle tuber viroid in Tomato in New Zealand
Authors: Elliott D. R. , Alexander B. J. R. , Smales T. E. , Tang Z. , Clover G. R. G.
Published: May 2007

During May 2000, symptoms resembling those of Potato spindle tuber viroid (PSTVd) infection were observed in glasshouse tomatoes (cv. Daniella) growing on one site in Tuakau, South Auckland, New Zealand. Symptoms appeared 2 to 3 months after planting, were confined to plant tops, and included leaf interveinal chlorosis, epinasty, and brittleness. Affected plants comprised ≍10% of the crop and were located near access points. PSTVd was identified in symptomatic plants by the Dutch Plant Protection Service and confirmed by mechanical transmission and grafting to tomato cv. Rutgers and reverse transcription polymerase chain reaction (2). The sequenced genome of this isolate (Accession AF369530) was 358 nt in length and had the closest homology to a Dutch isolate (Accession X17268). Electron microscopy did not reveal the presence of any viruses in affected plants and specific tests for other tomato pathogens were negative. A survey of 50 tomato glasshouse facilities throughout New Zealand revealed three further infected sites, two located close to the original site and one in Nelson, some 480 km distant. However, a survey of field-grown potato crops within 1.5 km of the original outbreak site did not reveal the presence of the viroid. PSTVd is seed transmitted and was probably introduced in glasshouses by use of infected seed. Glasshouse tomatoes are an important crop in New Zealand and annual production is currently 40,000 tonnes. The yield of affected plants may be decreased by up to 80% if suitable controls are not implemented (1).

References: (1) S. Kryczynski et al. Phytopath. Polonica 22:85, 1995. (2) A. M. Shamloul et al. Can. J. Plant Pathol. 19:89, 1997.
First Report of Infection of Kiwifruit by Pestalotiopsis sp. in Turkey
Authors: Karakaya A.
Published: May 2007

Circular to irregular brown leaf spots, 0.2 to 1.5 cm in diameter, were commonly observed on kiwifruit (Actinidia deliciosa) cv. Hayward plants in the Artvin-Arhavi region of northeastern Turkey. Leaf spots sometimes covered large portions of infected leaves, giving them a blighted appearance. Fruit symptoms consisted of brown, sunken, shriveled areas that were 0.5 to 3 cm in diameter. A fungus, later identified as a Pestalotiopsis sp. (1), was consistently isolated from diseased tissues. Pathogenicity tests were performed on 2-year-old kiwifruit plants and mature fruits at 18/22°C (day/night). A spore suspension (1 × 106 conidia per ml) was sprayed on leaves of 2-year-old kiwifruit plants. Agar pieces, 3 mm in diameter, from 10-day-old cultures also were applied to the leaves. Controls were treated with water and agar alone. Plants were covered with plastic bags for 3 days to ensure high humidity. After 2 weeks, disease symptoms were observed on inoculated leaves. Pestalotiopsis sp. was consistently isolated from these regions. Agar pieces from 10-day-old cultures were placed in small wounds made on the surfaces of mature, surface-disinfested fruits. Controls were treated with agar pieces alone. Softening of tissues next to the wound was observed 1 week after inoculation. Pestalotiopsis sp. was isolated from these areas. No symptoms were observed on noninoculated leaves or fruits. It was concluded that this disease is caused by Pestalotiopsis sp. This is the first report of its occurrence in Turkey.

Reference: (1) T. R. Nag Raj. Coelomycetous anamorphs with appendage bearing conidia. Mycologue Publications, Ontario, Canada, 1993.
Cuban Isolate of Bean golden yellow mosaic virus is a Member of the Mesoamerican BGYMV Group
Authors: Echemendía A. L. , Ramos P. L. , Peral R. , Fuentes A. , González G. , Sanpedro J. , Morales F.
Published: May 2007

In Cuba, the emergence of bean golden mosaic was associated with high populations of Bemisia tabaci in common bean (Phaseolus vulgaris L.) plantings in the 1970s (1). During the last two decades, the disease has caused significant economic losses, forcing some growers to abandon bean production. In Holguín, one of the main bean producing provinces of the country, about 2,000 ha of beans were abandoned in 1991 due to the high incidence of this whitefly-transmitted virus. At that time, yield losses associated with this disease reached 90 to 100% in farmer's fields. In spite of various control measures, the disease affected 33, 28, and 6.5% of the total area planted in Cuba to common bean in 1990, 1992, and 1996, respectively. For this investigation, common bean leaves showing systemic yellowing symptoms were collected in fields located in the provinces of Havana, Matanzas, and Holguín during 1998-1999. Sap and total DNA leaf extracts were used to inoculate healthy bean plants by manual and biolistic procedures, respectively. Characteristic yellowing symptoms were more efficiently reproduced using a particle gun device than by manual inoculation (18/20 plants and 5/20 plants, respectively, for a Holguín virus isolate). DNA extracts were further analyzed by polymerase chain reaction using two degenerate primer sets: PAL1v1978-PAR1c715 and PAL1c1960-PAR1v722 (2). Fragments of approximately 1.4 and 1.2 kb were amplified and cloned. Restriction fragment length polymorphism analysis of the cloned 1.4-kb fragments was performed with BglII, HincII, SalI, EcoRI, PstI, and XbaI, indicating that selected isolates from the three Cuban provinces shared identical restriction patterns. The nucleotide sequence obtained from two clones of a virus isolate from Holguín, was compared to sequences available for other begomoviruses using BLAST. The Cuban isolate shared up to 94% nt sequence identity with various strains of Bean golden yellow mosaic virus (BGYMV) in the first 250 nt of the rep gene. For the common region (CR), scores were 93% for BGYMV-GA (Guatemala), 92% for BGYMV-MX (southern Mexico) and BGYMV-PR (Puerto Rico), and 91% for BGYMV-DR (Dominican Republic). The iterative sequence ATGGAG was identified in the CR of the Cuban BGYMV isolate, as reported for other BGYMV isolates. Finally, the Cuban begomovirus, hereafter referred to as BGYMV-CU, shared nt and aa sequence identities of 94 and 100%, respectively, with the coat protein gene of BGYMV-MX. We conclude that the begomovirus isolated from mosaic-affected common bean plants in the province of Holguín is a member of the Mesoamerican BGYMV group (3).

References: (1) N. Blanco and C. Bencomo. Cienc. Agric. 2:39, 1978. (2) M. R. Rojas et al. Plant Dis. 77:340, 1993. (3) Morales and Anderson, Arch. Virol. 146:415, 2001.
First Report of Phomopsis longicolla from Velvetleaf Causing Stem Lesions on Inoculated Soybean and Velvetleaf Plants
Authors: Li S. , Bradley C. A. , Hartman G. L. , Pedersen W. L.
Published: May 2007

Reddish brown lesions were observed on the lower stem and upper root area of velvetleaf (Abutilon theophrasti Medik.) plants growing in an Illinois soybean field in June 2000. The lesions were similar in appearance to those caused by Rhizoctonia root rot of soybean. Stems and roots with lesions were cut into ≍5-mm pieces, surface-disinfested, and placed on 2% water agar at pH 4.5. The cultural morphology of the two isolates fit the description of Phomopsis longicolla Hobbs (1). Colonies on potato dextrose agar (PDA) were floccose, dense, and white. The undersides of the cultures were colorless. Stromata were large, black, and spreading. The pattern of stromata in one isolate was effuse, and most of the stromata were immersed or semiimmersed in the medium, whereas the stromata from the other isolate were massive and prominent. Neither isolate turned green on PDA. Alpha conidia were hyaline, ellipsoidal to fusiform, and guttulate. DAPI (4′,6-diamidino-2-phenylindole)-stained alpha conidia were uninucleate. Beta conidia and perithecia did not occur on either PDA or oat flakes on water agar from 1 to 10 weeks at 25°C under a 12-h photoperiod. The DNA sequences of the mitochondrial small subunit rRNA genes of the two isolates were identical and shared 100% sequence identity with two P. longicolla soybean isolates that we had identified previously. Pathogenicity tests were conducted in a greenhouse by cutting the stems of 3-week-old soybean and velvetleaf plants at the second internode. Mycelial plugs (4 mm in diameter) from the margin of 1-week-old cultures of the two isolates from velvetleaf and one from soybean were individually placed mycelial side down directly on the top of cut stems of 10 to 15 plants per isolate. Controls included noninoculated plants with and without PDA plugs. Plants were kept in a mist chamber in the dark at 25°C for 4 days and were then transferred to a greenhouse with a 16-h photoperiod at 24 ± 3°C. Stem lesions were measured 7 days after inoculation. The experiment was repeated once. Mean stem lesion lengths caused by the velvetleaf and soybean isolates were 23 and 20 mm, respectively, on soybean stems, while negative controls produced no lesions. Mean stem lesion lengths caused by the velvetleaf and soybean isolates were 23.5 and 12 mm, respectively, on velvetleaf stems. P. longicolla was reisolated from the stem lesions of five randomly collected plants. This is the first report of P. longicolla being isolated from velvetleaf and causing stem lesions on inoculated soybean and velvetleaf plants.

Reference: (1) T. W. Hobbs et al. Mycologia 77: 535, 1985.
Gradients of Primary and Secondary Infection byMonilinia vaccinii-corymbosifrom Point Sources of Ascospores and Conidia
Authors: Cox K. D. , Scherm H.
Published: May 2007

Spread of mummy berry disease of blueberry, caused by Monilinia vaccinii-corymbosi, occurs in two discrete monocycles; primary infection by ascospores results in shoot blight, while secondary infection of open flowers by conidia leads to fruit mummification. Gradients of primary and secondary infection from point sources of ascospores and conidia placed in separate plant rows were recorded in each of 2 years at two sites with no history of the disease. Primary infection gradients were longer downwind than upwind, with 95% of blighted shoots occurring within 30 m of the ascospore point source. This observation, along with a positive correlation (r = 0.852, P = 0.0072, n = 8) between the distance over which shoot blight occurred and wind speed parallel to the row, supports the role of wind as a key factor in ascospore dispersal. By contrast, secondary infection gradients were shorter downwind and longer upwind, with 95% of infected fruit occurring within 20 m of the conidial point source. The shorter downwind spread of secondary infection, along with a nonsignificant correlation (r = -0.649, P = 0.0812, n = 8) between the distance over which infected fruit occurred and wind speed, suggests that factors other than wind are important in the transfer of conidia to open flowers; this could include conidial dispersal by bee pollinators, which have been shown previously to forage primarily upwind. Exponential and Pareto cumulative distribution functions were fitted to cumulative counts of blighted shoots and infected fruit to model spread of primary and secondary infection. The Pareto model, which is characterized by a longer tail and predicts more infection farther from the inoculum source, better fits the observed disease gradients in most cases.
First Report of Anthracnose Caused by Colletotrichum gloeosporioides on Gueroba in Brazil
Authors: Charchar M. J. d'A. , Anjos J. R. N. , Akimoto A. K.
Published: May 2007

Gueroba (Syagrus oleracea (Mart.) Becc.), a member of the family Arecaceae, is an important native palm tree in central Brazil and has great potential as a cultivated crop and ornamental plant (1). In July 1999, anthracnose symptoms were observed on several gueroba plants growing in a field in Planaltina, Federal District. Leaves showed spots or small circular to irregular, brown-to-black necrotic lesions, which generally coalesced as symptoms progressed. Tissue sections from leaves with symptoms were plated aseptically on potato dextrose agar (PDA). A fungus was consistently isolated from leaves of symptomatic plants and was identified as Colletotrichum gloeosporioides (Penzig) Penzig & Sacc. by P. F. Cannon of CABI Bioscience, Egham, UK, where a culture (IMI 384186) has been deposited. An isolate was tested for pathogenicity by inoculating 20 plants at the two-leaf stage by placing a mycelial PDA plug from a 10-day-old fungal culture on a previously wounded leaf. Noninoculated plants served as controls. Plants were enclosed in a plastic bag and incubated for 4 days at 26 ± 2°C and ≈100% relative humidity. Ten days after inoculation, plants developed leaf lesions similar to those observed in the field. Symptoms did not develop on the control plants. C. gloeosporioides was reisolated from 95% of the inoculated leaves, completing Koch's postulates. The pathogenicity test was repeated with the same results. To our knowledge, this is the first report of C. gloeosporioides causing anthracnose on gueroba in Brazil.

Reference: (1) H. Lorenzi. Page 288 in: Árvores Brasileiras. Plantarum. Nova Odessa, Brazil 1998.
First Report of Rhizomania of Sugar Beet in the Columbia River Basin of Washington and Oregon
Authors: Gallian J. J. , Wintermantel W. M. , Hamm P. B.
Published: May 2007

Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV) and vectored by the soilborne fungus, Polymyxa betae Keskin, is one of the most economically damaging diseases affecting sugar beet (Beta vulgaris L.) worldwide and has been found in most sugar beet-growing areas of the United States (2). During harvest in October 2000, sugar beet plants exhibiting typical symptoms of rhizomania (1) were found in a field near Paterson, WA. Sugar beet had been planted in the field in 1999 and 2000, but prior to this, the field had not been planted with sugar beet for approximately 20 years. Symptomatic roots from the field exhibited stunting, vascular discoloration, and proliferation of lateral rootlets. Leaves of affected plants were chlorotic. Four soil samples were taken from symptomatic areas of the field and diluted with an equal amount of sterile sand. Seeds of rhizomania-susceptible sugar beet cv. Beta 8422 were planted in the soil and sand mix and maintained in a controlled environment at 24°C and 12 h of daylight at one location and in the greenhouse at another. After 8 weeks, enzyme-linked immunosorbent assay (ELISA) was performed on roots of plants grown at each location. Triple-antibody sandwich (TAS) ELISA (Agdia, Inc., Elkhart, IN) was conducted at the University of Idaho, Twin Falls, ID and double-antibody sandwich (DAS) ELISA was performed at USDA-ARS, Salinas, CA, with antiserum specific for BNYVV (2). Two of four samples were positive for BNYVV in the ELISA tests at both locations based on absorbance values at least three times those of healthy controls. TAS-ELISA tests were conducted on roots collected in July 2001 from a field in Washington, 12.9 km from the first field, as well as from a field across the Columbia River near Boardman, OR. Samples from both fields tested positive for BNYVV. All three fields are within 24 km of one another. Four additional fields have subsequently been confirmed to be infected with BNYVV in this region, based on symptomology and ELISA. There are approximately 3,240 ha of sugar beet grown in the region, and growers have been advised as a result of this confirmation to plant resistant cultivars and increase the sugar beet rotation interval with nonhost crops to a minimum of 4 years.

References: (1) J. E. Duffus. Rhizomania. Pages 29–30 in: Compendium of Beet Diseases and Insects. E. D. Whitney and J. E. Duffus, eds. The American Phytopathological Society, St. Paul, MN, 1986. (2) G. C. Wisler et al. Plant Dis. 83:864, 1999.
Formation of Phytophthora infestans Oospores in Nature on Tubers in Central Mexico
Authors: Fernández-Pavía S. P. , Grünwald N. J. , Fry W. E.
Published: May 2007

Oospore formation by Phytophthora infestans in nature has been detected on potato leaflets in central Mexico (1), but there are no reports of oospore formation on tubers. A severe late blight epidemic occurred in Calimaya, Mexico, in fields where potato cv. Alpha was planted during the summer of 2000. Yield was reduced despite numerous applications of fungicide. Four hundred potato tubers left in the field were collected from the upper 10 cm of soil and examined for late blight symptoms. Tubers with soft and dry rot symptoms were observed, but symptoms of pink rot (Phytophthora erythroseptica) were not found. Four percent of the tubers showed late blight symptoms. Sections of 10 tubers with late blight symptoms were air-dried for 2 weeks in the laboratory and homogenized with a mortar and pestle. Glycerol was added to the homogenized tissue and observed microscopically. Aplerotic oospores (10 to 15 oospores per tuber) with amphyginous antheridia typical of P. infestans were observed. P. mirabilis morphologically similar to P. infestans is present in the area but it does not infect potato tubers. The number of oospores observed in our tuber sample was much lower than the number reported on leaflets (>1,000 oospores per leaflet) in the Toluca Valley. Low numbers of oospores have been reported on tubers artificially inoculated with P. infestans under field conditions (2). Infected tubers left in the field may act as a source of primary inoculum. To our knowledge, this is the first report of oospores of P. infestans found on tubers in Mexico under natural field conditions.

References: (1) M. E. Gallegly and J. Galindo. Phytopathology 48:274, 1958. (2) A. Levin et al. Phytopathology 91:579, 2001.
First Report of Gray Leaf Spot on Perennial Ryegrass Turf in California
Authors: Uddin W. , Viji G. , Stowell L.
Published: May 2007

Gray leaf spot of perennial ryegrass (Lolium perenne L.) turf was first reported in the United States in 1991. The disease epidemic was primarily confined to golf course fairways in southeastern Pennsylvania (1). Subsequently, moderate to severe outbreaks of gray leaf spot occurred in perennial ryegrass fairways and roughs in numerous locations throughout the eastern and midwestern United States. In August 2001, a serious decline of perennial ryegrass turf was observed in a bermudagrass (Cynodon dactylon (L.) Pers) baseball field in Dodger Stadium in Los Angeles, CA, that had been overseeded with perennial ryegrass. The bermudagrass turf was not affected. The perennial ryegrass turf developed necrotic lesions that resulted in blighting of leaf blades. In laboratory assays, Pyricularia grisea (Cooke) Sacc., was consistently isolated from symptomatic ryegrass blades from turf samples collected from the site. Of the 12 P. grisea isolates collected from the assayed leaf blades, five isolates were selected for a pathogenicity assay. Twenty-five ‘Legacy II’ perennial ryegrass plants were grown from seeds in 4 × 4 in.-plastic pots, (10 × 10 cm) which were filled to 1 cm below the rim with granular calcine clay medium (Turface MVP, Allied Industrial Material Corp., Buffalo Grove, IL). Three weeks after seeding, plants were fertilized with a water-soluble 20-20-20 N-P-K fertilizer (1.3 g/liter of water) once per week. Treatments (isolates of P. grisea and a control) were arranged as a randomized complete block design with five replications. Five-week-old plants were sprayed with an aqueous suspension of P. grisea conidia (≈5 × 104 conidia per ml of sterilized distilled water with 0.1% Tween 20) using an atomizer until the leaves were completely wet. Plants sprayed with sterilized distilled water served as the control. After inoculation, individual pots were covered with clear polyethylene bags and placed in a controlled environment chamber maintained at 28°C and continuous fluorescent light (88 μE m-2 s-1). Four days after inoculation, necrotic lesions (<2 mm diameter) developed on ryegrass blades inoculated with each isolate of P. grisea. Lesions did not develop on leaves of control plants. Seven days after inoculation, the polyethylene bags were removed, and 50 symptomatic blades from each pot were collected, and disease incidence (percent infected leaves) and severity (index 0 to 10; 0 = none, 10 = >90% of the leaf blade necrotic ) were assessed. P. grisea was isolated from symptomatic leaves of plants inoculated with the fungus. Disease incidence and severity on inoculated plants were 92 to 96% and 8.8 to 10, respectively. There were no significant differences in disease incidence and severity (P = 0.05) among the isolates of P. grisea included in the test. To our knowledge, this is the first report of gray leaf spot of perennial ryegrass turf in California.

Reference: (1) P. J. Landschoot and B. F. Hoyland. Plant Dis. 76:1280, 1992.
Variations ofLeek yellow stripe virusConcentration in Garlic and Its Incidence in Argentina
Authors: Conci Vilma C. , Lunello Pablo , Buraschi Diana , Italia Rusell R. , Nome Sergio F.
Published: May 2007

The purpose of this work was to determine variations in titer of Leek yellow stripe virus (LYSV) throughout the crop cycle and bulb storage, and to evaluate the incidence of infected plants in the main garlic-production regions of Argentina. One hundred plants with LYSV from each of five cultivars were analyzed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) in six different vegetative stages in White- and Red-type garlic cultivars and seven stages in cv. Rosado Paraguayo, throughout the year. In two White-type garlic cultivars, LYSV showed peaks of viral concentration in May, at the beginning of the crop cycle, and in November, just before harvest. In two Red-type garlic selections, an increase was detected in November (period of bulbing). The highest virus titers for these four garlic cultivars were detected in devernalized clove. In Rosado Paraguayo, the peak virus concentration occurred in September prior to harvesting. In a survey at 14 different localities in Argentina, 3,066 random samples were analyzed. LYSV was found in 80 to 98% of the plants from all regions, except in Santa Cruz, where 34% of plants were infected. The importance of this study is that it allows us to recommend the most suitable moment of the year to make the analysis with DAS-ELISA.
Survival and Persistence of Alternaria dauci in Carrot Cropping Systems
Authors: Pryor B. M. , Strandberg J. O. , Davis R. M. , Nunez J. J. , Gilbertson R. L.
Published: May 2007

Alternaria dauci was recovered in California from carrot crop residue and from volunteer carrot plants in fallow carrot fields. The fungus was not recovered from common weeds surrounding fallow fields. To evaluate further the survival of A. dauci on carrot crop residue, infected carrot leaf tissue was placed in fields or in soil in greenhouse pots, and recovered over time. In California, A. dauci was recovered from infected leaf tissue in both fallow and irrigated fields for as long as 1 year. In Florida, A. dauci was recovered from infected leaf tissue in fallow fields for up to 30 weeks. In greenhouse experiments, A. dauci was recovered from infected leaf tissue for as long as 1 year in dry soil, but only up to 30 weeks in soil that was watered weekly. To determine the infectivity of A. dauci borne on carrot crop residue, infected carrot crops were incorporated into organic and mineral field soils, and soil samples were collected over time. Carrot seed were planted in collected soil, and seedling infection by A. dauci was recorded. Seedling infection was detected up to 13 and 14 weeks after crop incorporation in organic and mineral soil, respectively. Seedling infection was detected for up to 5 weeks in soil that remained dry compared with 3 weeks in flooded soil.
Relationships of Environmental and Cultural Factors with Severity of Gray Leaf Spot in Maize
Authors: Bhatia Alka , Munkvold G. P.
Published: May 2007

Gray leaf spot of maize caused by Cercospora zeae-maydis is a major foliar disease in the United States and other parts of the world. Efficient management of gray leaf spot is hindered by a lack of quantitative information regarding environmental and cultural influences on disease severity. We collected environmental, cultural, and disease severity data in southern Iowa at 13 locations in 1998 and 11 locations in 1999. The independent variables that we considered included temperature, relative humidity, leaf wetness, percent maize residue cover, distance to nearest maize residue, planting date, and previous crop. A time-duration value (TDV) variable was created to represent cumulative hours of favorable temperature (22 ≤ T ≤ 30°C) and relative humidity (≥95%). Disease severity was assessed at 2-week intervals on three to eight maize genotypes differing in gray leaf spot resistance and maturity at each location. Environmental, cultural, and disease data were summarized for four different periods during the growing season and analyzed by stepwise multiple linear regression in order to determine which variables significantly contributed to gray leaf spot severity at the dough or dent growth stages of maize. In 1998, genotype resistance, planting date, distance to nearest maize residue, wetness duration, and TDV had significant effects on disease severity. R2 values were similar among the four periods. The best-fitting model for the 1998 data had an R2 of 0.65. With 1998 and 1999 data combined, results were similar except that percent maize residue cover was significant rather than distance to nearest maize residue. The best-fitting model had an R2 of 0.55. The 2-year model utilizing only the weather variables from emergence to 2 weeks before silking had an R2 value of 0.43. Strong linear relationships existed between gray leaf spot severity and genotype resistance, maize surface residue, planting date, and TDV. These results can serve as a foundation for the development of a prediction model for gray leaf spot severity on maize.
First Report of Fomitiporia punctata Infecting Kiwifruit
Authors: Elena K. , Paplomatas E. J.
Published: May 2007

During 2000 and 2001, a wood discoloration and decay of 10- to 12-year-old kiwifruit vines (Actinidia deliciosa (Chev.) Liang & Ferguson) was observed in vineyards in all major kiwifruit-growing areas of Greece. Leaves became chlorotic or necrotic, dry, and abscised prematurely. Fruits dropped before reaching full maturity. Necrosis of shoots and twigs progressed from the shoot tips toward the trunk. If the infected twigs were pruned early, the vine occasionally produced new shoots. Cross sections of infected trunks and shoots revealed a light-colored soft rot in the center, surrounded by brown, hard, necrotic wood resembling the esca disease of grapevine, caused by Fomitiporia punctata. From the white rotted areas, a fungus was isolated that formed a dense aerial mycelium with cream-yellow to light-brown colonies on potato dextrose agar (PDA). The fungus was identified as F. punctata (Fr.) Murrill by M. Fischer, Weinbauinstitut, Freiburg-Germany, (personal communication). Pathogenicity tests were performed by artificially inoculating 2-year-old healthy kiwifruit (cv. Hayward) plants. The inoculum consisted of a 7-mm diameter mycelial plug taken from the margin of a 10-day-old culture of F. punctata growing on PDA. A portion of the bark was partially raised from the trunk, and the inoculum was inserted under the bark. The bark was tied with adhesive tape to keep the inoculum in place and sealed with Vaseline to prevent dehydration. Ten plants were inoculated while 10 were used as nonincoculated controls. Wilting of lower leaves was first observed 15 days after inoculation. In longitudinal sections, a brown discoloration on the stem wood was observed 46 days after inoculation in all inoculated vines, while control plants remained healthy. However, the same fungus was isolated from only one infected plant. Low frequency in reisolating F. punctata is often mentioned in the literature (3). Although esca on kiwifruit has been reported in Italy, the fungus initially was identified as Phellinus conchatus and subsequently as F. punctata (1,2). To our knowledge, this is the first published report of F. punctata causing wood decay of kiwifruit.

References: (1) F. Calzarano et al. Inf. Fitopatol. 49:12, 1999. (2) S. Di Marco et al. N. Z. J. Crop Hortic. Sci. 28:69, 2000. (3) L. Sparapano et al. Phytopathol. Mediterr. 39:46, 2000.
First Occurrence of Downy Mildew on Digitalis purpurea (Common Foxglove), Caused by Peronospora digitalidis, in California and the United States
Authors: Tjosvold S. A. , Koike S. T.
Published: May 2007

In California, Digitalis purpurea (common foxglove) and D. grandiflora (yellow foxglove) are grown as cutflower, potted, and landscape plant commodities. In the spring of 2002, after seasonably wet and cool weather, severe downy mildew was observed on potted common foxglove plants in commercial nurseries in coastal California (Santa Cruz County). Initial symptoms on leaves consisted of light green, rectangular areas that were vein-delimited and measured 2 to 5 × 8 to 12 mm. Such spots later became chlorotic. As disease progressed, chlorotic spots coalesced and turned necrotic. The purple-gray sporulation of the pathogen could be seen primarily on abaxial leaf surfaces. However, in some cases, extensive fungal growth developed on adaxial surfaces of lower leaves. Conidiophores branched dichotomously and measured 278 to 520 μm long from the lower end to the first branches and 11 to 14 μm across at the widest part of the swollen base. Branch ends were slender with curved tips that measured 11 to 22 μm long. Conidia were hyaline, ellipsoid to ovoid, and measured 22 to 31 μm × 17 to 19 μm. Oospores were not observed. The pathogen was identified as Peronospora digitalidis (1,2). Pathogenicity tests were not conducted. However, the consistent association of sporulation with symptoms, the internal hyphal growth giving rise to conidiophores, and the obligate nature of Peronospora pathogens clearly indicated that P. digitalidis was the causal agent of this disease. Field observations indicated that D. purpurea cvs. Alba and Apricot and Foxy hybrids were very susceptible, D. × mertonensis ( = D. grandiflora × D. purpurea) appeared to be moderately susceptible, and D. grandiflora grown in the same area was symptomless. One planting of Foxy hybrid was 100% infected, and the entire lot of several hundred plants was discarded. The disease also was found on Foxy hybrid seedlings grown in propagation greenhouses. To our knowledge, this is the first report of downy mildew caused by P. digitalidis on cultivars of D. purpurea in California and the United States. This disease has been reported previously in Europe, Asia, and New Zealand (1,2).

References: (1) G. Hall. Mycopathologia 126:47, 1994. (2) E. H. C. McKenzie and J. M. Dingley. N. Z. J. Bot. 34:263, 1996.
Geographic Distribution, Cultivar Susceptibility, and Field Observations on Bentgrass Dead Spot
Authors: Kaminski John E. , Dernoeden Peter H.
Published: May 2007

Bentgrass dead spot (BDS) is a disease of creeping bentgrass incited by Ophiosphaerella agrostis. This project was designed to determine the susceptibility of field-grown bentgrass cultivars to BDS and to gather information regarding the geographic distribution and field conditions favoring the disease. In a field cultivar evaluation trial, all major Agrostis spp. used on golf courses, including colonial, creeping, and velvet bentgrasses, were shown to be susceptible to an isolate of O. agrostis. Velvet bentgrass cvs. SR7200 and Bavaria were among the most and least susceptible cultivars, respectively. Among creeping bentgrass cultivars, L-93 generally was the most susceptible and Pennlinks, Penncross, and Crenshaw were among the least susceptible. Although recovery of BDS patches in the autumn was slow, Bardot colonial bentgrass and Crenshaw, Imperial, L-93, and Penn G-6 creeping bentgrasses showed the most rapid recovery prior to winter. Variation in the virulence of isolates and the potential for races of the pathogen, however, may affect cultivar susceptibility. The disease was most commonly found on 1- to 4-year-old golf greens and disease severity declined 1 to 3 years after it first appeared. BDS only was found on sand-based greens, collars, and tees and has not been observed in bentgrass grown on native soil. Between 1998 and 2001, O. agrostis was isolated from diseased leaves, roots, crowns, and stolons of creeping bentgrass and hybrid bermudagrass turf samples received from 13 states. The disease was most severe in sunny and exposed locations, especially on ridges, mounds, and slopes. In the mid-Atlantic region, BDS appeared as early as May and remained active as late as December. The disease was most active in July and August, and usually became inactive with the advent of frost in October.
Effect of Formulated Yeast in Suppressing the Liberation of Botrytis cinerea Conidia
Authors: Cook Darryl W. M.
Published: May 2007

Eight yeast isolates that bound directly to Botrytis cinerea germlings were assessed for the ability to suppress spore liberation of conidia from B. cinerea. After the yeast cell suspension from each isolate was mixed with cellulose and dried, the product was milled into a fine powder. This yeast-cellulose formulation was applied as a dry powder to sporulating B. cinerea colonies on kiwifruit (Actinidia deliciosa) leaf disks, where the particles from the formulation attached to conidiophores and conidia. Some of these formulations significantly suppressed the liberation of conidia from treated colonies. Suppression of conidial liberation could provide another management tool for the biological control of sporulating B. cinerea with applications during late epidemic development. Using α-cellulose prepared with Candida pulcherrima in the conditions imposed in the present study, there was an approximately 50% reduction in the number of conidia released with the treatment of the B. cinerea lesions. The suppression of disease through a reduction in the population of liberated conidia is discussed.
Identification of the Fungal Endophyte Epichloe festucae in the Fine Fescue Festuca ampla
Authors: Zabalgogeazcoa I. , Criado B. García , Bony S.
Published: May 2007

Festuca ampla is native to the Iberian Peninsula (4). Endophytic mycelium was observed by microscopy (2) in stem pith samples of two of eight asymptomatic plants of F. ampla collected in one population from a natural grassland in Salamanca, Spain. The fungus could be isolated (2) only from these two plants, and conidiophores and reniform conidia typical of Epichloe species (3) were observed in pure cultures. The two infected plants maintained in pots outside, developed ectostromata in some reproductive stems (choke disease) the year after the field sampling. Six seeds collected from an infected plant were germinated, and all six seedlings were found to be infected based on microscopy (2), implying seed transmission of the endophyte. These observations suggest that this is a pleiotropic symbiont, having both mutualistic and pathogenic states in its host. An ergovaline concentration of 120 ng/g dry weight was detected in a sample of leaves and leaf sheaths of an infected plant. All of the above characteristics are typical of the genus Epichloe, and in particular of the fine fescue endophyte E. festucae (1,3). To determine the species, internal transcribed spacer and 5.8-rDNA sequences as well as a partial sequence of the β-tubulin gene were obtained. These two sequences (EMBL Accession Nos. AJ488497 and AJ488498) showed 100% sequence homology to the corresponding sequences in E. festucae. To our knowledge, this is the first report of this endophyte species in the grass F. ampla.

References: (1) L. P. Bush et al. Plant Physiol. 114:1, 1997. (2) E. M. Clark et al. J. Microbiol. Methods 1:149, 1983. (3) A. Leuchtmann et al. Mycologia 86:802, 1994. (4) I. Markgraff-Dannenberg. Festuca. Pages 125–153 in: Flora Europaea, Vol 5. Cambridge University Press, Cambridge, 1980.
First Report of Web Blight Caused by Rhizoctonia solani on Catharanthus roseus in Louisiana
Authors: Holcomb G. E. , Carling D. E.
Published: May 2007

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.