bluuebunny/crossref_metadata_2025 huggingface dataset:
Rain Fastness and Persistence of Fungicides for Control of Alternaria Brown Spot of Citrus
Authors: Vicent A. , Armengol J. , García-Jiménez J.
Published: May 2007

Field persistence and simulated rain experiments were conducted to determine the residual activity and rain fastness of several fungicides used for the control of Alternaria brown spot of citrus. Fungicidal activity persisted well in simulated rain experiments, despite the high rainfall amounts tested (40 mm in 2004 and 90 mm in 2005). However, most of the fungicides showed a significant reduction of disease control on fruit of ‘Fortune’ mandarin in the orchard after natural rain in 2004. Fruit growth rate was low and did not appear to play an important role in decline of fungicide residues. Copper products showed longer residual activity on fruit and higher rain fastness than did mancozeb, difenoconazole, iprodione, famoxadone, and pyraclostrobin. Cuprous oxide and copper oxychloride SC provided satisfactory disease control on fruit through 28 days and withstood 71 mm of rainfall in the orchard. A 4-week schedule with copper compounds is proposed for disease control on Fortune fruit during periods of weather favorable for disease development. Respray to replace fungicide deposit seems to be necessary only after heavy or wind-driven rains. With this program, about half of the sprays applied per season for fruit protection could be saved compared with the current schedule in Spain.
Effects of Green Manure Type and Amendment Rate on Verticillium Wilt Severity and Yield of Russet Burbank Potato
Authors: Ochiai N. , Powelson M. L. , Dick R. P. , Crowe F. J.
Published: May 2007

Increasing restriction of agrochemicals is motivating development of ecology-based cropping systems, including green manures, to manage soilborne diseases. Green manures have shown promise in suppressing Verticillium dahliae, but information about effect of different green manures and optimal application rates remains limited. Therefore, we conducted two single-year field experiments comparing effects of Austrian winter pea (Pisum sativum ‘Melrose’), broccoli (Brassica oleracea var. botrytis ‘Excelsior’), and Sudan grass (Sorghum vulgare var. sudanense ‘Monarch’), amended at 6, 12, or 24 Mg ha-1, on soil populations and root infection by V. dahliae, wilt severity, and yield of Russet Burbank potato. Inoculum density was reduced relative to the nonamended, infested control by all broccoli treatments, Austrian winter pea applied at 12 and 24 Mg ha-1, and Sudan grass applied at 12 Mg ha-1. Root infection was not reduced by any green manure treatment. Median wilt severity was reduced approximately 70% by all green manures applied at 24 Mg ha-1 and 74% by Austrian winter pea applied at 12 Mg ha-1. Tuber yield was reduced approximately 20% in nonamended, V. dahliae-infested controls relative to the noninfested controls. No green manure treatment improved yield relative to the nonamended, infested control.
Effects of Propamocarb Hydrochloride on Mycelial Growth, Sporulation, and Infection by Phytophthora nicotianae Isolates from Virginia Nurseries
Authors: Hu Jiahuai , Hong Chuanxue , Stromberg Erik L. , Moorman Gary W.
Published: May 2007

Propamocarb hydrochloride is a systemic fungicide commonly used for control of Phytophthora diseases of nursery crops. Here we report on the effect of this compound on different growth stages of Phytophthora nicotianae, a major pathogen of numerous herbaceous and some woody ornamental plants. A total of 71 isolates were assayed for sensitivity to propamocarb at two concentrations of 1.8 mg/ml (label rate) and 10 mg/ml using clarified V8 agar as a base medium. All isolates grew at 10 mg/ml with the most sensitive isolate having 34.8% relative growth compared with growth on nonamended medium. Nine isolates were selected and further tested for mycelial growth at 0, 1, 10, 25, 50, and 100 mg/ml, and for sporangium production, zoospore motility, and germination at 0, 5, 50, 500, 5,000, and 50,000 μg/ml. EC50 values ranged from 2.2 to 90.1 mg/ml for mycelial growth, 133.8 to 481.3 μg/ml for sporangium production, 88.1 to 249.8 μg/ml for zoospore motility, and 1.9 to 184.6 μg/ml for zoospore germination, respectively. In addition, 17 selected isolates were evaluated for propamocarb sensitivity on Pelargonium × hortorum cv. White Orbit. Two days after seedlings were treated with propamocarb at 3.6 mg/ml, they were inoculated by either inverting one 5-mm-diameter plug of a 3-day-old culture or applying a 10-μl drop containing 20 zoospores onto each cotyledon. Propamocarb hydrochloride provided good protection of geranium seedlings from zoospore infections but not from mycelial infections. These results suggest that this fungicide must be used preventively for Phytophthora disease management and that mycelial growth may not be the most reliable measurement to determine the development of fungicide resistance to this compound in Phytophthora species at production facilities and in the landscape.
Variation in Bentgrass Susceptibility to Typhula incarnata and in Isolate Aggressiveness Under Controlled Environment Conditions
Authors: Chang S. W. , Chang T. H. , Abler R. A. B. , Jung G.
Published: May 2007

Typhula incarnata, the causal agent of gray snow mold, is an important winter pathogen of turfgrasses in the northern United States. The relative susceptibility of cultivars of three bent-grass species (creeping, colonial, and velvet bentgrass) to Typhula incarnata and the aggressiveness of 15 T. incarnata isolates obtained from infected turfgrasses on golf courses in Michigan, Minnesota, and Wisconsin were evaluated under controlled conditions. A hypersensitive type of resistance response to T. incarnata was not observed in any cultivar. Disease severity increased with higher inoculum concentration of T. incarnata. Colonization by gray snow mold gradually decreased with increasing plant age from 11 weeks after seeding in most cultivars tested, suggesting that age-related resistance was expressed over time. There were significant differences in disease severity among the three bentgrass species, particularly between tetraploid (creeping and colonial) and diploid (velvet) species, and among cultivars within each species, indicating varying levels of susceptibility to T. incarnata. All 15 isolates were pathogenic on bentgrass and were significantly different in aggressiveness, but aggressiveness was not related to geographic origin. Therefore, turfgrass breeders should be able to use one or a few virulent representative isolates of the pathogen to screen for resistance.
First Report of Black Foot Disease of Grapevine Caused by Cylindrocarpon macrodidymum in Chile
Authors: Auger J. , Esterio M. , Pérez I.
Published: May 2007

Black foot disease, caused by Cylindrocarpon macrodidymum Halleen, Schroers & Crous, is reported damaging table and wine grapes (Vitis vinifera L.) for the first time in Chile. During the summer of 2006, 2- to 5-year-old grapevines showed reduced vigor, shortened internodes, and drying and dying shoots along with abnormal development of roots with growth parallel to the soil surface, necrotic root crowns, and development of secondary roots. Internal necrosis extended from the bark to the pith in diseased parts of the plants. Other symptoms included black discoloration of the wood, gum inclusions in xylem vessels, black streaks in the vascular tissue, and reduction in root biomass, with sunken, necrotic root lesions. Eighteen Cylindrocarpon isolates were collected from roots, vascular elements, and pith tissue of grapevines cultivars (Flame Seedless, Red Globe, Thompson Seedless, Merlot, Carmenere, and Cabernet Sauvignon) from 12 locations in Chile. The isolates were identified on the basis of morphological features. All isolates produced micro- and macroconidia (one to three septa) and chlamydospores in short and intercalary chains (1,4), and by internal transcribed spacer (ITS1-5,8S-ITS4) rDNA and β -tubulin (BT1, and BT2) partial sequences, identical to those of C. macrodidymum (isolate USS074, GenBank Accession No. AY 997558 and isolate USSO150, GenBank Accession No. AY 997598) (2). Phylogenetic analyses placed these isolates in a clade closely related, but clearly distinct from other clades, to C. destructans and C. liriodendri (2,3). Pathogenicity tests were completed by drench inoculation onto 50 6-month-old rooted cuttings of ‘Red Globe’ with 25 ml of conidia suspension (106 conidia ml-1) obtained from four isolates. Ten control cuttings of ‘Red Globe’ were inoculated with an equal volume of sterile distilled water. The plants were incubated for 4 months in a controlled environment facility at 24°C. All isolates tested were pathogenic. In addition, they caused significant root rot (t-test of disease incidence, P = 0.0048) and no significant level of variation was detected between different isolates. C. macrodidymum was reisolated from the region of brown streaking in all the inoculated cuttings and was not isolated from the water-treated controls. To our knowledge, this is the first report of C. macrodidymum causing black foot disease on grapevine in Chile.

References: (1) C. D. Booth. Mycol. Pap. (CMI) 104:1, 1966. (2) F. Halleen et al. Stud. Mycol. 50:431, 2004. (3) F. R. Mantiri et al. Can. J. Bot. 79:334, 2001. (4) E. Petit and W. D. Gubler. Plant Dis. 89:1051, 2005.
Comparing Disease Predictors and Fungicide Programs for Late Blight Management in Celery
Authors: Bounds R. S. , Hausbeck M. K.
Published: May 2007

Late blight, incited by the fungus Septoria apiicola, is the most important foliar disease of celery in Michigan and results in necrotic lesions on leaves and petioles that can reduce yield up to 80%. Most celery growers apply the fungicide chlorothalonil as frequently as every 7 days to protect the crop; however, some of these applications may not be needed when environmental conditions do not favor disease development. The purpose of this study was to evaluate disease predictors using a standard (chlorothalonil) and a reduced-risk (azoxystrobin alternated with chlorothalonil) fungicide program for managing late blight on ‘Dutchess’ celery in 2003 to 2005. Fungicides were initiated 1 week after transplanting and reapplied every 7 days or according to the Septoria, Cercospora, or TOM-CAST predictors. The TOM-CAST predictor was tested using 10, 15, and 20 disease severity values (DSV) as thresholds for fungicide application. In each year of this study, timing sprays according to the TOM-CAST 10-DSV predictor resulted in disease control comparable with the 7-day interval, but required up to five fewer sprays and reduced fungicide costs up to $215/ha. The Septoria, Cercospora, and TOM-CAST 15-DSV predictors often provided control similar to the 7-day interval, but these predictors were somewhat inconsistent compared with TOM-CAST 10-DSV. The TOM-CAST 20-DSV predictor required the fewest number of sprays but unacceptable levels of disease resulted. The standard and reduced-risk fungicide programs frequently provided similar control; however, azoxystrobin alternated with chlorothalonil was more effective than chlorothalonil alone when disease pressure was high.
Genetic Characterization of Binucleate Rhizoctonia Species Causing Web Blight on Azalea in Mississippi and Alabama
Authors: Rinehart T. A. , Copes W. E. , Toda T. , Cubeta M. A.
Published: May 2007

Web blight on containerized azalea is an annual problem for commercial nurseries during summer months in the southern United States. Losses to web blight are associated with the cost of fungicide applications, delayed marketing of diseased plants, and plant death. Two hundred and eleven isolates of binucleate Rhizoctonia were recovered from azalea leaves with web blight symptoms from two nurseries in Mississippi and Alabama over 3 years. The internal transcribed spacer region (ITS) of the ribosomal DNA (rDNA) was sequenced from all isolates to determine genetic identity. A single anastomosis group (AG) of binucleate Rhizoctonia represented 92% of the samples collected from infected leaves. Genetic data and hyphal fusion experiments confirmed that these isolates belong to AG-U, which was recently identified from root and stem infections on miniature rose in Japan. Isolates of binucleate Rhizoctonia belonging to anastomosis groups AG-R, CAG-7 (=AG-S), and AG-G were also identified in the sample in low frequency. This is the first report of the occurrence of binucleate Rhizoctonia AG-U in the United States.
First Report of Spirea Witches'-Broom Disease in China
Authors: Gao R. , Wang J. , Li X. D. , Zhu X. P. , Tian G. Z.
Published: May 2007

Bumald spirea (Spiarea bumalda Burv.) is an important ornamental tree widely grown in northern China. In August of 2006, spirea plants exhibiting symptoms of witches'-broom, stunting, yellowing, and shoot dieback were found at an incidence of 5 to 15% in Qingzhou City, Shandong Province, China. Total DNA was extracted separately from 0.1 g of phloem tissue from leaf midribs and stems of six symptomatic and six asymptomatic plants with a modified cetyltriethylammonium bromide (CTAB) method (3). Resulting DNA samples were analyzed for phytoplasma DNA by a nested PCR assay using phytoplasma universal 16S rDNA gene primer pairs R16mF2/R16mR1 and R16F2n/R16R2 (2). These primers amplified 1.5- and 1.2-kb products, respectively, from DNA of all symptomatic plants only. Restriction fragment length polymorphism (RFLP) analysis of the 1.2-kb 16S rDNA product using enzymes AluI, MseI, and HhaI indicated that all symptomatic plants contained a group 16SrI (aster yellows group) subgroup B (16SrI-B) phytoplasma strain (4). A 16S rDNA sequence derived from this strain (GenBank Accession No. EF176608) was most similar (99.8 and 99.6%) to those of severe aster yellows (GenBank Accession No. M86340) and Maryland aster yellows (GenBank Accession No. AF322644) phytoplasmas, respectively, thereby confirming strain identity based on RFLP analysis. A phytoplasma (Spiarea stunt phytoplasma, GenBank Accession No. AF190228), which belongs to X-disease group (16SrIII), was reported to infect spirea and probably be lethal to S. tomentosa in New York (1,4). The phytoplasma reported here shared low identity (90.8%) with Spiarea stunt phytoplasma, but also caused dieback of spirea shoots. The epidemiology and economic impact of this disease need further intensive investigation. To our knowledge, this is the first report of spirea witches'-broom disease and of its association with a subgroup 16SrI-B phytoplasma in China.

References: (1) H. M. Griffiths et al. Can. J. Plant Pathol. 16:255, 1994. (2) D. E. Gundersen and I.-M. Lee. Phytopathol. Mediterr. 35:144, 1996. (3) Y. Qi et al. Biotechnol. Bull. 4:44, 2004. (4) The IRPCM Phytoplasma/Spiroplasma Working Team-Phytoplasma Taxonomy Group. Int. J. Syst. Bacteriol. 54:1243, 2004.
First Report of Colletotrichum gloeosporioides Causing Anthracnose Fruit Rot of Trichosanthes kirilowii in China
Authors: Li H. Y. , Zhang Z. F.
Published: May 2007

Trichosanthes kirilowii Maxim., a species within the gourd family, is cultivated in China for its edible seeds and medicinal roots. Since 2000, heavy losses due to fruit rot have been caused by a new disease with typical anthracnose symptoms, i.e., water-soaked, dark brown-to-black, sunken lesions. Signs of the suspected pathogen were usually seen on near-mature fruits and were especially evident after abundant rainfall. The lesions contained numerous black acervuli with black setae that produced abundant, salmon-colored spore masses under high relative humidity. Dark lesions on leaves and stems could also be found in the field that sometimes led to stem girdling and wilting. Conidia produced in acervuli were 14 to 20 × 3 to 6 μm, straight, cylindrical, hyaline, aseptate, with both ends rounded. Conidiophores were 13 to 22 × 4 to 6 μm, aseptate, and cylindrical, while the setae, usually with three to five septa, measured 60 to 86 × 5 to 6 μm. The pathogen was initially identified as Colletotrichum gloeosporioides on the basis of the morphology (2). In culture, the fungus produced a gray-to-black colony with whitish aerial mycelium on potato dextrose agar (PDA) medium. Pathogenicity was tested by inoculating the equator of 10 fruits of T. kirilowii with a 5-day-old mycelia plug from a single-spore colony (0.5 cm in diameter); fruits inoculated with the plugs of PDA medium served as the control. Inoculated fruits were covered with plastic for 24 h to maintain high relative humidity. After 4 days, 100% of the inoculated fruits showed symptoms identical to those observed on T. kirilowii fruit affected in the field, while all fruits inoculated with PDA medium remained free of symptoms. Reisolation of the fungus from fruit lesions confirmed that the causal agent was C. gloeosporioides. To confirm the pathogen to species, the C. gloeosporioides-specific primers CgInt/ITS4 and C. acutatum-specific primers CaInt2/ITS4 (1) were used to amplify the sequence of internal transcribed spacer regions. A fragment of approximately 500 bp was only amplified with primers CgInt/ITS4 and the sequence (GenBank Accession No. AM491334) was 98 to 100% matched to the sequences of several C. gloeosporioides isolates (e.g., GenBank Accession Nos. AJ301919, AB255249, AJ301908), whereas the sequence shares 86 and 91% identity to that of C. orbiculare (GenBank Accession No. AB042308) and C. acutatum (GenBank Accession No. AJ749675), respectively. Thus, we concluded that C. gloeosporioides is the causal agent of anthracnose fruit rot of T. kirilowii. To our knowledge, this is the first report of C. gloeosporioides infecting T. kirilowii.

References: (1) A. E. Brown et al. Phytopathology 86:523, 1996. (2) B. C. Sutton. The Coelomycetes. CAB International Publishing, New York, 1980.
First Report of Blueberry Botrytis Blight in Buenos Aires, Entre Ríos, and Córdoba, Argentina
Authors: Vasquez P. , Baldomá J. A. , Wright E. R. , Pérez A. , de Sesar M. Divo , Pérez B. A.
Published: May 2007

Since 2003, a new field disease has been observed on several cultivars of highbush blueberry (Vaccinium corymbosum L.) in Buenos Aires (Baradero, Colonia Urquiza, Lima, Mercedes, and San Pedro), Entre Ríos (Concordia, Gualeguaychú, and Larroque), and Córdoba (Capilla del Monte and La Cumbre). Infected flowers turned brown to tan with a water-soaked appearance and shriveled up. Blighted flowers typically did not produce fruits; even an entire cluster of berries could be aborted. A chlorotic area, that later became necrotic and turned light brown, developed when leaves were in contact with blighted flowers. A watery rot developed on fruit occasionally before harvest but more generally after harvest. Infected tender green twigs also became blighted, with leaf tissue becoming brown to black. Older twigs and stems were also blighted. Abundant, gray mycelium with conidial masses developed on all affected tissues under moist conditions. Sections of infected leaves, twigs, stems, flowers, and fruits were surfaced sterilized with 0.2% NaOCl, plated on 2% potato dextrose agar (pH 7), and incubated at 22°C. Pure cultures formed a whitish dense mycelial mat and turned gray after 72 h. Conidia were ellipsoid, hyaline, nonseptate, and formed on botryose heads. They ranged from 5.8 to 9 × 8.1 to 13.7 μm (average 8.6 × 10.2 μm). Black, round, and irregular microsclerotia developed on 7-day-old cultures with an average size of 1.1 × 1.7 mm. Morphological characteristics agree with those described for Botrytis cinerea Pers.:Fr (1). Pathogenicity was tested on 10 12-month-old potted blueberry plants cv. O'Neal by spraying a suspension of 1 × 106 conidia per ml of sterile distilled water. Ten plants used as controls were sprayed with sterile distilled water. Each plant was covered with a transparent polyethylene bag for 48 h and incubated at 20 ± 2°C in humid chambers for 15 days. Lesions similar to those observed in the fields developed after 4 days and asexual fructifications developed after 5 days. The same pathogen was reisolated from the lesions, thus completing Koch's postulates. Water-treated plants remained symptomless. To our knowledge, this is the first report of a disease caused by B. cinerea on blueberry in Buenos Aires, Córdoba, and Entre Ríos provinces of Argentina.

References: (1) M. V. Ellis and J. M. Waller. Sclerotinia fuckeliana (conidial state: Botrytis cinerea) No. 431 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1974.
Prune, Plum, and Nectarine as Hosts of Trichothecium roseum in California Orchards
Authors: Hong C. X. , Michailides T. J.
Published: May 2007

Trichothecium roseum (Pers.:Fr.) Link was frequently observed (up to 21%) on mummified peach (Prunus persica (L.) Batsch), nectarine (P. persica (L.) Batsch var. nectarina (Aiton) Maxim.), plum (P. salicina Lindl.), and prune (P. domestica L.) fruits in orchards during a 1995 to 1996 survey. Pink mold rot caused by T. roseum was also frequently observed (at about the 1 to 2% level) on a number of samples of prune fruit collected from commercial orchards in Glenn, Butte, Madera, Fresno, and Tulare counties in 1996, after storage at 4°C for 7 days and then 20°C for 4 days. Wounded and nonwounded prune (cv. French), plum (cv. Casselman), peach (cv. Fairtime), and nectarine (cv. Spring Bright) fruits were infected after inoculation with a drop (20 μl) of T. roseum suspension (5 × 105 conidia/ml). Characteristic pink sporulation covered the surface of most fruit 7 days after inoculation. Conidia of T. roseum completely covered all wounded and nonwounded prune fruit, sparsely on the wounded plum fruit, and densely on both wounded and nonwounded peach and nectarine fruits (lesion diameter = 1 to 7 cm) 2 weeks after inoculation. T. roseum sporulated more rapidly and better on the fruits that were contaminated with either Monilinia fructicola (G. Wint.) Honey, or a Cladosporium sp. Peach has been listed as a host of T. roseum (California Plant Disease Host Index, Part 1: Fruits and Nuts, A M. French, ed., 1987), but this is the first report on the pathogenicity of this fungus on prune, plum, and nectarine from California.
Planting Date, Fungicide, and Cultivar Effects on Sclerotinia Crown and Stem Rot Severity in Alfalfa
Authors: Sulc R. M. , Rhodes L. H.
Published: May 2007

This study was conducted to determine the effect of planting date, fungicide, and cultivar on severity of Sclerotinia crown and stem rot (SCSR) and subsequent productivity of alfalfa. The cultivars Armor and A9109 were seeded no-till in May, early August, mid August, and late August 1993 and 1994 in a sod uniformly infested with sclerotia of Sclerotinia trifoliorum. Four applications of the fungicide vinclozolin effectively controlled the disease. Averaged over years and cultivars, disease severity (percentage of plot area affected) in the no-fungicide treatment was 4, 12, 23, and 41% for the spring, early August, mid August, and late August plantings, respectively. Armor had higher disease severity than A9109 in the 1993 seeding, but not in the 1994 seeding. Forage yield the year after seeding reflected differences in disease severity ratings. The risk of severe SCSR damage in no-till summer seedings of alfalfa can be reduced dramatically if stands become established early enough so plants reach at least 10 weeks of age by the time apothecia emerge in the fall.
Natural Field Spread of Mild and Severe Isolates of Citrus Tristeza Virus in Florida
Authors: Powell C. A. , Pelosi R. R. , Bullock R. C.
Published: May 2007

The effectiveness of five different aphid control regimes in delaying movement of mild and severe isolates of citrus tristeza virus (CTV) into a CTV-free sweet orange scion on sour orange rootstock block was monitored annually for 5 years, using severe isolate-specific and isolate-nonspecific monoclonal antibodies. The average percentage of trees infected with a severe isolate of CTV was 32, 32, 20, 25, and 28 for trees treated with Temik, Temik + Meta-Systox R (MSR), MSR, stylet oil, or no aphid control, respectively, at the conclusion of the experiment (5 years). These percentages were not significantly different (P ≤ 0.05). The average percentage of trees infected only with mild isolates was 13, 10, 7, 7, and 17 for the above treatments, respectively. The infection with mild isolates was significantly greater (P ≤ 0.05) with no aphid control than with stylet oil or MSR treatments.
Frequency and Timing of Fungicide Applications for the Control of Gray Leaf Spot in Maize
Authors: Ward J. M. J. , Laing M. D. , Rijkenberg F. H. J.
Published: May 2007

Timing and frequency of fungicide treatments for management and control of gray leaf spot of maize, caused by Cercospora zeae-maydis, were quantified with the logistic model and area under disease progress curve (AUDPC). Control was most effective when spraying commenced as disease severity levels reached 2 to 3% of the leaf area blighted and when lesions were restricted to the basal five leaves of the maize plant. Highest grain yields were achieved with treatments providing disease control until the crop was physiologically mature. To provide this length of control, the frequency and number of fungicide applications varied with the stage of host development when disease was first apparent; with early infections, more fungicide treatments were necessary to provide protection until physiological maturity. Yield responses to fungicides appeared to be a function of the growth stage of the host when sprays were initiated, the amount of disease at spray date, the length of fungicide control, and effective control through to physiological maturity.
Influence of Nematicide Application on the Severity of the Root-Knot Nematode-Fusarium Wilt Disease Complex in Cotton
Authors: Colyer P. D. , Kirkpatrick T. L. , Caldwell W. D. , Vernon P. R.
Published: May 2007

Eight cotton cultivars, with and without aldicarb treatment, were evaluated for their effect on the severity of the root-knot nematode-Fusarium wilt disease complex in cotton. A randomized complete block design with a split-plot arrangement of treatments was used with cotton cultivars as the main plots and nematicide treatments as the subplots. Results in 1994 and 1995 were similar. Yield of lint, boll weight, and wilt and root-gall ratings were different among cultivars and between nematicide treatments both years. Increased lint yield and boll weight, and reduced root-gall and wilt ratings were associated with application of aldicarb. Increased lint percentage was associated with application of aldicarb in 1994, but not in 1995. Fiber micronaire, elongation, uniformity, and strength were different among cultivars, but not between nematicide treatments. Fiber length (UHM; Upper-Half Mean) was different among cultivars and was higher in the aldicarb-treated plots in both years. Numbers of Meloidogyne incognita second stage juveniles and eggs extracted from soil samples were lower in the aldicarb-treated plots in July, but not at harvest, both years. Population densities of M. incognita were not different among cultivars, except the mid-season sample in 1995.
A Greenhouse Technique for Assessing Phytophthora Root Rot Resistance in Glycine max and G. soja
Authors: Pazdernik D. L. , Hartman G. L. , Huang Y. H. , Hymowitz T.
Published: May 2007

New sources of soybean (Glycine max) resistance to Phytophthora sojae are needed to provide effective resistance because of the rapidly changing race patterns of P. sojae in fields. The objectives of our study were to develop a method to screen Glycine soja for resistance to P. sojae and then use this methodology to screen G. soja lines for resistance to P. sojae races 1, 3, and 20. An agar plug-inoculation method, in which a 3-mm-diameter mycelial plug of the fungus was placed mycelium side down on cotyledons of 10-day-old soybean seedlings, was directly compared with the traditional hypocotyl inoculation method. There was no significant difference between the hypocotyl- and plug-inoculation methods when tested on four soybean differential lines using three P. sojae races. The plug-inoculation method then was used to screen 430 G. soja accessions for resistance to P. sojae race 3. Nine G. soja accessions were retested with races 1, 3, and 20. Of the 430 G. soja accessions tested, 22 accessions had survival rates higher than 75% and nine had rates higher than 90% against race 3. Additionally, five of the nine accessions that were tested again had greater than 60% survival against races 1, 3, and 20. These results suggest that the plug-inoculation method can be used as an alternative to the hypocotyl-inoculation method. Potential sources of new P. sojae resistance and/or tolerance may be present in G. soja, but additional genetic research is needed to determine if these sources are different from sources currently found in G. max.
Using PCR to Distinguish Diaporthe phaseolorum and Phomopsis longicolla from Other Soybean Fungal Pathogens and to Detect Them in Soybean Tissues
Authors: Zhang A. W. , Hartman G. L. , Riccioni L. , Chen W. D. , Ma R. Z. , Pedersen W. L.
Published: May 2007

Restriction fragment length polymorphism analyses of polymerase chain reaction (PCR) amplified DNA were used to distinguish Diaporthe phaseolorum and Phomopsis longicolla isolates from other soybean fungal pathogens. Primers made to the conserved sequences of nuclear ribosomal DNA amplified the internal transcribed spacer (ITS) regions of D. phaseolorum var. meridionalis and P. longicolla. The PCR products were cloned and then sequenced. Specific-primers, Phom.I and Phom.II, were designed from the polymorphic regions of D. phaseolorum and P. longicolla isolates from soybean to distinguish them from other soybean fungal pathogens. These ITS-derived primers amplified a 337-bp-specific DNA fragment from P. longicolla, D. phaseolorum var. meridionalis, D. phaseolorum var. caulivora, D. phaseolorum var. sojae, and Phomopsis spp. from 20 different hosts. No amplified product was observed using DNA of seven other soybean fungal pathogens or soybean DNA. The detection limit of PCR using primers Phom.I and Phom.II was 2.5 × 10-7 dilution of fungal DNA extracted from samples of 10 pooled seeds and as low as a 1:15 (Phomopsis:soybean) ratio when using 10 ng of DNA per μl from each P. longicolla and soybean. PCR did not produce products using primers Phom.I and Phom.II with DNA extracted from noninfected seeds, but specific bands were observed from samples of 10 pooled seeds and from individually infected seeds. A specific band was observed as well from DNA extracts of tissue samples from symptomless plants inoculated with P. longicolla and D. phaseolorum var. sojae.
Identification of the Wheat Curl Mite as the Vector of the High Plains Virus of Corn and Wheat
Authors: Seifers Dallas L. , Harvey Tom L. , Martin T. J. , Jensen Stanley G.
Published: May 2007

Wheat with virus-like symptoms (extracts containing a 33-kDa protein in sodium dodecyl sulfate-polyacrylamide gel electrophoresis, negative in enzyme-linked immunosorbent assay to wheat streak mosaic virus, and not infectious in a backassay to other wheat) reacted positively to antiserum made against a protein purified from symptomatic corn infected with the High Plains virus (HPV), indicating a serological relationship between the corn and wheat pathogens. The wheat curl mite (WCM, Aceria tosichella Keifer) was identified as the vector of the virus and caused persistent infection of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) in greenhouse experiments. The HPV was recovered in the field from naturally infected wheat where the number of HPV-infected plants decreased with increasing distance from the WCM source in volunteer wheat.
Susceptibility of Ponderosa Pine to Endocronartium harknessii and Other Causes of Mortality in Pennsylvania
Authors: Egan A. F. , Merrill W.
Published: May 2007

The effects of Endocronartium harknessii on provenances of Pinus ponderosa planted in 1969 on a coal strip-mine spoil bank in central Pennsylvania were reassessed. In 1982 infection levels among seed sources ranged from 4.9 to 52.5%. In 1991 infection levels ranged from 29 to 95%, and mortality due to rust infection ranged from 9 to 58% among these seed sources. Levels of infection, mortality due to rust infection, and mortality unrelated to rust infection differed significantly among seed sources (P < 0.001, < 0.001, and = 0.023, respectively). Among geographic ecotypes, there were no significant differences among percentages of trees infected (P = 0.094), but there were significant differences among trees surviving outplanting (P = 0.007), mortality due to rust (P = 0.004), and mortality unrelated to rust (P < 0.001). Only one provenance incurred less than 40% infection, indicating that virtually none of these types of provenances are suitable for reforestation in areas of eastern North America where E. harknessii occurs.
Long-term Effect of Temperature and Triadimefon on Proliferation of Uncinula necator: Implications for Fungicide Resistance and Disease Risk Assessment
Authors: Ypema H. L. , Gubler W. D.
Published: May 2007

Triadimefon has been used in California to control Uncinula necator, causal agent of grape powdery mildew, since 1982. Instances of unsatisfactory control have occurred mainly in the cooler coastal areas of California. The effect of temperature and application of triadimefon was investigated over a 53-day-period on two U. necator isolates, sensitive and resistant to triadimefon. At 15°C, 25°C, or temperatures fluctuating between 15 and 25°C, in absence of triadimefon, the isolates continued to produce high numbers of conidia for the entire duration of the experiment. Sporulation declined at daily maximum temperatures of 32°C for 6 h, 36°C for 3 h, and 40°C for 1 h, but was detectable when the experiment was terminated. At these temperature regimes, sporulation of the triadimefon-treated sensitive isolate ceased after 23 days. When treated with triadimefon, sporulation of the resistant isolate was comparable to that of the water-treated control. At daily maximum temperatures of 32°C for 11 h, 36°C for 6 h, and 40°C for 3 h, sporulation of both isolates generally ceased after 23 days, regardless of triadimefon application. Triadimefon resistance is most likely to manifest itself under high disease pressure, which is in part a function of temperature. The duration of daily maximum temperatures may be a valuable addition to disease risk assessment models.
Recent Outbreak of Fusarium Wilt of Basil in Florida
Authors: Datnoff L. E. , Liang L. Z. , Wick R. L.
Published: May 2007

Symptoms of wilt, leaf chlorosis, leaf drop, and shoot and plant death were observed in commercial fields of basil (Ocimmum basilicum L.). Disease incidence ranged from 10 to 80% among individual fields. Initial isolations from infected stem tissue were made on water agar amended with streptomycin sulfate. Single-spore isolates transferred onto corn leaf agar were identified as Fusarium oxysporum Schlechtend.:Fr. f. sp. basilicum Dzidzariya. Pathogenicity tests were performed on 10-cm-tall basil plants, cv. Siam Queen, for three Florida isolates and one Massachusetts isolate. An inoculum concentration of 1 × 106 conidia per ml was applied to soil around the roots. Symptoms of wilt, external stem discoloration, and death of basil occurred after 14 days, and F. oxysporum f. sp. basilicum was reisolated from plants inoculated with all four isolates. Controls were disease-free. Identification of the isolates as F. oxysporum f. sp. basilicum was done with a set of DNA primers developed by Pan and Wick (2) for a 0.7-kb DNA fragment unique to this pathogen. This report confirms the existence of F. oxysporum f. sp. basilicum in Florida (1), and identifies this disease as a potential threat to commercial basil production.

References: (1) S. A. Alfieri et al. Diseases and Disorders of Plants in Florida. Bull. No. 14. Fla. Dept. Agric. Consumer Serv., 1993. (2) Z. Pan and R. L. Wick. Phytopathology 85:1559, 1995.
First Report of Fusarium solani f. sp. cucurbitae Race 1 in Spain
Authors: García-Jiménez J. , Armengol J. , Moya M. J. , Sales R.
Published: May 2007

A crown, root, and fruit rot of squash (Cucurbita maxima Duchesne) was first observed in 1995 and again in 1996 in several fields in the eastern provinces of Valencia and Castellón. When plants approach maturity they exhibited a severe cortical rot at the base of the stem and the upper portion of the taproot causing yellowing and wilting of the leaves. Within a few days of the first symptoms of crown rot, affected plants usually died. Soft, circular lesions developed where fruit were in contact with soil. Isolations on potato dextrose agar supplemented with 0.5 mg/ml of streptomycin sulfate (PDAS) from the crown of symptomatic plants and fruits yielded primarily a Fusarium sp. Isolates were transferred to potato sucrose agar (PSA) and Bilay's medium, modified by Joffe (SNA), and incubated at 25°C for 10 days with a 12-h photoperiod. The isolates were identified as Fusarium solani (Mart.) Sacc. based on colony morphology on PSA and fungal morphology on SNA. C. maxima (cv. Dulce de Horno) seedlings (eight replicates per isolate) grown on a sterilized mixture of equal portions (vol/vol) of soil, sand, and peat moss were inoculated at the first true leaf stage by introducing a 10-ml spore suspension (106 spores per ml) at the base of plants. Symptoms appeared in 14 to 21 days as linear, coalescing, cortical lesions in the hypocotyl of inoculated plants and ultimately caused seedling death. There were no differences observed in the five isolates tested, regardless of origin. Mature fruits were inoculated by injecting spore suspension (106 spores per ml) into the mesocarp. Within 14 to 21 days after inoculation, lesions developed similar to those observed in the field. Stem isolates were pathogenic on the fruit, and fruit isolates were pathogenic on stems. Reference isolates NRLL 22165 and NRRL 22449 for race 1, and NRRL 20545 and NRRL 22144 for race 2, provided by K. O'Donnell, were also tested as positive controls. Only race 1 isolates caused seedling death. In each study, the fungus was reisolated, confirming Koch's postulates. Based on these results and disease symptoms in the field, the fungus was classified as F. solani f. sp. cucurbitae W. C. Snyder & H. N. Hans race 1, which causes a root, stem, and fruit rot, whereas race 2 causes only a fruit rot (1). F. solani also was isolated from seeds removed from diseased fruits. This is the first report of the presence of F. solani f. sp. cucurbitae race 1 in Spain.

Reference: (1) T. A. Tousson and W. C. Snyder. Phytopathology 51:17, 1961.
The Influence of Spray Adjuvants on Exacerbation of Citrus Bacterial Spot
Authors: Gottwald T. R. , Graham J. H. , Riley T. D.
Published: May 2007

The effect of adjuvants on the spread of Xanthomonas axonopodis pv. citrumelo applied to nursery plots of citrus (Citrus spp.) rootstock trees in simulated wind-blown rain was studied. Commercial adjuvants tested included a penetrant-surfactant, the penetrant or surfactant components of the penetrant-surfactant alone, an antitranspirant, a surfactant, or 1 of 3 formulations of a spreader-binder. Individual rows were treated with the adjuvants or water alone as a control. Bacterial dispersal gradients in all rows were similar and extended the entire 7 m of the nursery rows. Disease incidence, number of lesions per plant, and lesion diameters were determined at selected assay points in each row 28 days after the event. The penetrant-surfactant and its surfactant component significantly increased the total number of lesions per plant and mean lesion diameters compared to the water control. The disease gradient slopes associated with the penetrant-surfactant and its surfactant component were significantly flatter and more extensive than the water control. The penetrant component of the penetrant-surfactant, the antitranspirant, and two spreader-binders adjuvants did not significantly alter the disease gradient compared to the water control. Lesion sizes and numbers were also increased by a surfactant product and the surfactant component of the penetrant-surfactant, but not by the penetrant component of the penetrant-surfactant, the antitranspirant, or the three spreader-binder formulations. These results suggest that surfactants which induce stomatal flooding may enhance infection and exacerbate citrus bacterial epidemics.
First Report of Cucumber Mosaic Virus in Eryngium amethystinum, Canna spp., and Aquilegia hybrids in Ohio
Authors: Fisher J. R. , Sanchez-Cuevas M.-C. , Nameth S. T. , Woods V. L. , Ellett C. W.
Published: May 2007

Eryngium amethystinum (amethyst sea holly) is a herbaceous plant commonly grown as an ornamental perennial in U.S.D.A. hardiness zones 3 to 8. The plant thrives in dry areas with infertile soils and the flowers are often used in dried floral arrangements. Canna spp. (Canna), soft perennials (U.S.D.A. zone 9 and above), are becoming popular flowering plants because of their bright flowers and spectacular foliage. There are a variety of species that fall under the heading Canna spp., of which the most popular are C. glauca, C. indica, C. edulis, and C. iridiflora. Hybrids of Aquilegia (garden columbine), a hardy perennial (U.S.D.A. zones 3 to 9), flower in late spring through early summer. The genus is made up of a wide variety of cultivars. E. amethystinum exhibiting severe mosaic, yellowing, and stunting, along with Canna plants exhibiting severe stunting, chlorotic and distorted foliage, and mosaic, and garden columbine plants exhibiting stunting, leaf curl, chlorosis, and mosaic, collected from commercial plantings throughout the central Ohio area, were analyzed for the presence of virus infection with viral-associated, double-stranded RNA (dsRNA) analysis. dsRNA analysis resulted in a banding profile typical of that seen with members of the cucumovirus family of plant viruses. Plants positive for cucumovurus-like dsRNA were tested with a direct antibody sandwich enzyme-linked immunosorbent assay (ELISA). ELISA results confirmed the presence of cucumber mosaic virus (CMV) in all symptomatic plants tested. No evidence of dsRNA or CMV was found in any of the asymptomatic plants tested. Because all of these hosts are common in the perennial garden, they could serve as a reservoir host of CMV for other plants in the garden. This is the first report of CMV in E. amethystinum, Canna spp., and Aquilegia hybrids in Ohio.
Cucumber Mosaic Virus Associated with Leaf Malformation and Stunting in Adiantum pedatum
Authors: Nameth S. T. , Steininger J.
Published: May 2007

Adiantum pedatum (maidenhair fern) is a fern commonly used in landscapes and interiorscapes for its attractive foliage. A. pedatum is quite hardy and under conditions of good soil fertility it can become highly intrusive if left unchecked. Maidenhair fern showing symptoms associated with possible virus infection were collected from the Chadwick Arboretum on the campus of The Ohio State University, Columbus. The leaves of the affected plants were slightly malformed such that the pinnules were arranged irregularly at the pinna. The sequence of the pinnae on the rachis and the general appearance of the rachis were distorted. Overall, the symptoms observed were not as severe as those described by Nienhaus et al. on other species of ferns (1). Viral-associated double-stranded RNA (dsRNA) analysis was used to analyze tissue from symptomatic and asymptomatic plants for evidence of virus infection. Results of dsRNA analysis gave evidence of a possible cucumovirus. There was no evidence of dsRNA in the asymptomatic tissue. Symptomatic tissue was subsequently tested for cucumber mosaic virus (CMV) with a direct antibody sandwich, enzyme-linked immunosorbent assay (ELISA). ELISA results were positive for CMV in symptomatic tissue and negative for CMV in asymptomatic tissue. This is the first report of a virus associated with a disease in A. pedatum.

Reference: (1) F. Nienhaus et al. Z. Pflanzenkrankh. Pflanzenschutz 9:533, 1974.
The First Report of the Teleomorph of Colletotrichum acutatum in the United States
Authors: Guerber J. C. , Correll J. C.
Published: May 2007

Colletotrichum acutatum J. H. Simmonds is an important pathogen with a worldwide distribution and is involved in diseases and disease complexes of a number of economically important hosts (2). Three taxa, namely C. acutatum, C. gloeosporioides (Penz.) Penz. & Sacc. in Penz. (self-sterile/heterothallic isolates), and Glomerella cingulata (Stoneman) Spaulding & H. Schrenk (self-fertile/homothallic isolates), are involved in bitter rot disease of apple in the southeastern U.S. The three species can be distinguished based on morphological criteria, growth rates, and mtDNA restriction fragment length polymorphisms (RFLPs) (1,3). In studies of sexual compatibility, isolates of C. acutatum from apple readily produced perithecia in artificial culture on a minimal agar salts medium under continuous light when mated with isolates of C. acutatum that belonged to different vegetative compatibility groups. Sexual recombination between parental isolates was confirmed by examination of the segregation of genetic markers (nitrate nonutilizing [nit] mutants, sulfate nonutilizing [sul] mutants, and chromogenic pigmentation) among randomly collected ascospore progeny. No perithecia were observed when isolates of C. acutatum were crossed with homothallic isolates of G. cingulata or heterothallic isolates of C. gloeosporioides. Several isolates of C. acutatum from apple and one from blueberry that produced perithecia in mating studies had an identical or very similar mtDNA RFLP haplotype. Efforts are underway to characterize the teleomorphic form of C. acutatum.

References: (1) J. C. Correll et al. Phytopathology 83:1412, 1993. (2) P. R. Johnston and D. Jones. Mycologia 89:420, 1997. (3) Y. Shi et al. Plant Dis. 80:692, 1996.
Expansion of Cankers Caused byLeucostoma cinctaon Sweet Cherry Trees
Authors: Barakat R. M. , Johnson D. A.
Published: May 2007

Wounds made in July 1987 and fresh pruning cuts made monthly from August 1989 to July 1990 on sweet cherry trees were inoculated with Leucostoma cincta. Infection occurred each month, with a higher percentage of wounds becoming infected during the spring and summer than during the winter months. Inoculation with conidia placed directly on wounds or inoculation with pruning shears contaminated with conidia and mycelia resulted in the same incidence and severity of cankers. Canker enlargement was related to increasing monthly temperature. Greatest canker enlargement usually occurred from April through August. The period of least canker enlargement occurred from October through January. The largest cankers resulted from inoculations in July, and the smallest cankers resulted from inoculations in November, December, and January. Canker expansion curves were significantly described by cubic or quadratic equations for inoculation made during 10 of 12 months.