bluuebunny/crossref_metadata_2025 huggingface dataset:
Managing Bacterial Speck and Spot of Tomato with Acibenzolar-S-Methyl in Virginia
Authors: Graves A. S. , Alexander S. A.
Published: May 2008

On the Eastern Shore of Virginia, copper compounds, which have been used for controlling bacterial disease on tomato, have been associated with pesticide run-off from commercial tomato production with copper toxicity causing losses in clam nurseries. The objective of this study was to identify and evaluate a replacement for copper that was safer for the environment and could provide effective management of bacterial diseases of tomato. Acibenzolar-S-methyl (Actigard 50 WG), a plant activator that induces systemic acquired resistance (SAR), was compared to the standard bactericide (copper hydroxide + mancozeb) for controlling Xanthomonas axonopodis pv. vesicatoria and Pseudomonas syringae pv. tomato. Plots were established in grower fields in a randomized complete block design with four replications. Acibenzolar-S-methyl, at a rate of 10.5-g a.i./ha was equal to or better than the standard copper-based bactericide for controlling bacterial speck and spot, with no adverse affect on yield. Replacing copper with acibenzolar-S-methyl would effectively eliminate the need for copper bactericides. In environmentally sensitive areas where copper toxicity can be a problem, acibenzolar-S-methyl can providean effective alternative for the management of bacterial speck and bacterial spot on tomato.

Accepted for publication 26 January 2002. Published 20 February 2002.
Biological Control of Plant Pathogens: Research, Commercialization, and Application in the USA
Authors: Gardener Brian B. McSpadden , Fravel Deborah R.
Published: May 2008

In a narrow sense, biocontrol suppresses pest organisms with other organisms. However, the multiple interactions among organisms and their environment can contribute to effective biological control. Future prospects for using biological control of plant pathogens in both conventional and organic agriculture are described.

Accepted for publication 3 May 2002. Published 10 May 2002.
Toxicity of Indian Mustard and Allyl Isothiocyanate to Masked Chafer Beetle Larvae
Authors: Noble Ryan R. P. , Harvey Stephanie G. , Sams Carl E.
Published: May 2008

Alternatives for control of soil-inhabiting pests are needed due to the phase-out of methyl bromide. One possible alternative is using the pesticidal properties of compounds released by macerated Brassica tissues. In this study, larvae of masked chafer beetles (Cyclocephala spp.) were placed in soil amended with Brassica juncea L. (PI 458934) tissue. Allyl isothiocyanate (AITC) levels were positively correlated to larval mortality, with the 8% B. juncea treatment resulting in 100% larval mortality with an average AITC concentration of 11.4 mg per liter of soil atmosphere. Although B. juncea produces high levels of AITC, the mass of tissue required for significant insecticidal activity against Cyclocephala spp. also is high, between 4 and 8% of soil mass for this plant accession.

Accepted for publication 23 May 2002. Published 10 June 2002.
Citrus Canker: The Pathogen and Its Impact
Authors: Gottwald Tim R. , Graham James H. , Schubert Tim S.
Published: May 2008

The U.S. has seen an increase in introductions of invasive plant pests into agricultural crops. In Florida, one such invasive species is a bacterial plant pathogen that causes Asiatic citrus canker. Its eradication has received considerable press attention and legal challenges, has produced far-reaching political and socioeconomic impact in Florida, and has implications for national and international trade.

Accepted for publication 17 July 2002. Published 12 August 2002.
Phytophthora Blight on Pumpkin
Authors: Babadoost Mohammad , Islam Sayed Z.
Published: May 2008

P. capsici can strike cucurbit plants at any stage of growth. The infection usually appears first in low areas of the fields where soil remains wet longer. The pathogen infects seedlings, vines, leaves, and fruit. Phytophthora damping-off may result in partial to total loss of the crop.

Accepted for publication 18 November 2002. Published 16 December 2002.
Natural Occurrence of the Entomopathogenic Fungus Nomuraea rileyi in the Soybean Green Semilooper, Chrysodeixis acuta, in India
Authors: Gupta Ved Prakash
Published: May 2008

Nomuraea rileyi (Farlow) Samson is an entomopathogenic fungus that infects lepidopteran larvae. The fungus was observed in populations of the soybean green semilooper, Chrysodeixis acuta, in the humid Southeastern Plain Zone of Rajasthan, India, in 2001.

Accepted for publication 16 December 2002. Published 13 January 2003.
Effect of Diseases on Soybean Yields in the United States and Ontario (1999 to 2002)
Authors: Wrather J. A. , Koenning S. R. , Anderson T. R.
Published: May 2008

Soybean yields in the U.S. and Ontario have often been suppressed by diseases. The resulting losses are important to rural economies and to the economies of allied industries in urban areas. The authors compiled estimates of soybean yield losses due to diseases for each soybean producing state in the U.S. and Ontario from 1999 to 2002. The goal was to provide this information to help funding agencies and scientists prioritize research objectives and budgets.

Accepted for publication 4 March 2003. Published 25 March 2003.
First Report on the Incidence of Mixed Infections of Impatiens necrotic spot virus (INSV) and Tomato spotted wilt virus (TSWV) in Tobacco Grown in Georgia, South Carolina, and Virginia
Authors: Martínez-Ochoa N. , Csinos A. S. , Whitty E. B. , Johnson A. W. , Parrish M. J.
Published: May 2008

Tomato spotted wilt caused by Tomato spotted wilt virus (TSWV) continues to be a serious disease problem on tobacco (Nicotiana tabacum L.), peanut (Arachis hypogaea L.), tomato (Lycopersicon esculentum Mill.), and pepper (Capsicum annum L.) in the southeastern United States. Impatiens necrotic spot virus (INSV, formerly known as TSWV-I) is an emerging virus found mostly in greenhouse production of ornamentals and is also vectored by thrips. A few years ago INSV was detected in peanut in Georgia and Texas and its occurrence appears to be increasing). Mixed infections of TSWV and INSV in tobacco have been observed within the last two years in North Carolina and Kentucky. Our objective was to sample several locations in Georgia, Florida, South Carolina and Virginia to confirm and report the presence of natural TSWV and INSV mixed infections in tobacco.

Accepted for publication 14 March 2003. Published 17 April 2003.
Spatial Patterns of Fusarium Head Blight in New York Wheat Fields Suggest Role of Airborne Inoculum
Authors: Del Ponte Emerson M. , Shah Denis A. , Bergstrom Gary C.
Published: May 2008

The spatial pattern of Fusarium head blight (FHB) incidence was studied in 70 winter wheat fields in New York over a period of 3 years. Incidence of FHB was randomly distributed among 60 sampling areas in 64 of the 70 fields. Fields with random FHB ranged from 0.05 to 23% in average incidence of FHB and followed bean, cabbage, corn, oat, pea, sorghum, and soybean. There was strong evidence of aggregation in FHB only in three fields that had large concentrations of corn debris. Many fields had small, scattered fragments of corn debris in evidence from a corn crop two or more years prior to wheat. The lack of aggregation in FHB and low incidences of FHB in these fields suggests that weathered corn debris contributed relatively little within-field inoculum for FHB. Based on the predominantly random patterns of FHB, disease in rotational wheat fields of New York appears to be initiated primarily by deposition of spores from diffuse atmospheric populations of G. zeae. We hypothesize that these airborne spores may originate largely from inoculum sources external to wheat fields. Over-wintered corn residue, especially from the preceding crop season, on the soil surface is the most likely potential source of regional atmospheric inoculum for FHB in New York.

Accepted for publication 10 March 2003. Published 18 April 2003.
Chile Pepper and The Threat of Wilt Diseases
Authors: Sanogo Soum
Published: May 2008

The popularity of chile peppers is providing a boost to the chile industry, but production is increasingly constrained by chile plant diseases. This article briefly describes four diseases that lead to wilting in chile: Phytophthora root rot, Verticillium wilt, Rhizoctonia root rot, and Fusarium wilt.

Accepted for publication 18 April 2003. Published 30 April 2003.
First Report of Downy Mildew of Chives Caused by Peronospora destructor in the Pacific Northwest
Authors: Glawe Dean A.
Published: May 2008

Chive (Allium schoenoprasum L.) is one of the specialty crops grown by farmers in the Puget Sound region of Washington State. In September, 2002, downy mildew symptoms were observed in a 0.2 hectare field planting of chive near Fall City, King County, WA. Downy mildew had not been reported previously on chive in the Pacific Northwest.

Accepted for publication 15 April 2003. Published 12 May 2003.
Wilt of Radish Caused by Fusarium oxysporum f. sp. raphani in Washington State
Authors: du Toit L. J. , Pelter G. Q.
Published: May 2008

Radish (Raphanus sativus L.) seed crops in Washington may annually produce up to 70% of the US and up to 40% of the world supply of radish seed. In May and June 2002, severe symptoms of wilting and dieback were observed in a radish stock seed crop in the Columbia Basin of central Washington. Examination of the roots revealed a dark vascular discoloration and root rot, as well as cabbage maggot (Delia radicum L.) larvae with associated feeding injury. Because of the potential for widespread dissemination of seedborne pathogens, research is needed to determine whether F. oxysporum f. sp. raphani can be seedborne in radish.

Accepted for publication 12 May 2003. Published 16 June 2003.
Detecting Orobanche minor Seeds in Soil Using PCR
Authors: Patzoldt Megan E. , Chen Weidong , Diers Brian W.
Published: May 2008

A new set of soybean accessions from south-central China were added to the USDA germplasm collection in 1996. Previous studies have shown that accessions with high levels of resistance to brown stem rot (BSR) can be found in germplasm collected from central and southern China. The objective of this study was to screen these accessions and identify those with resistance to BSR. In a preliminary study, 85 of 623 accessions tested were identified as resistant to BSR. In the second study, these 85 accessions were challenged with multiple biotypes of Phialophora gregata f. sp. sojae to identify those accessions with the strongest resistance. From these two studies, ten accessions were identified that had BSR resistance equal to or greater than the current resistant sources.

Accepted for publication 10 June 2003. Published 1 July 2003.
Sudden Oak Death and Associated Diseases Caused by Phytophthora ramorum
Authors: Davidson J. M. , Werres S. , Garbelotto M. , Hansen E. M. , Rizzo D. M.
Published: May 2008

Diagnosis of Sudden Oak Death, ramorum leaf blight, and ramorum shoot dieback on a wide variety of hosts are discussed in detail, including the symptoms and signs, host range, taxonomy, and geographic distribution, as well as methods of isolation, identification, and storage of Phytophthora ramorum, the pathogen which causes Sudden Oak Death.

Accepted for publication 6 June 2003. Published 7 July 2003.
First Report of Powdery Mildew of Platanus occidentalis caused by Microsphaera platani (Erysiphe platani) in Washington State
Authors: Glawe Dean A.
Published: May 2008

American sycamore (Platanus occidentalis L.) is a common native species in eastern North America and is planted widely as a landscape tree in other regions. During a survey of powdery mildew diseases in Washington State, the fungus Microsphaera platani Howe was found on American sycamore trees in Madison Park, Seattle. This report documents the presence of M. platani in Washington State and presents information on the fungus.

Accepted for publication 30 July 2003. Published 18 August 2003.
First Report of Powdery Mildew of Nandina domestica Caused by Microsphaera berberidis (Erysiphe berberidis) in the Pacific Northwest
Authors: Glawe Dean A.
Published: May 2008

Nandina domestica is a bamboo-like landscape plant grown widely in the Pacific Northwest. In 2000 through 2002, powdery mildew was observed on landscape plants of N. domestica in cities in the Puget Sound region. Microscopic features of the fungus present in these specimens fit those of Microsphaera berberidis, previously reported from this host species in Scotland and California.

Accepted for publication 29 September 2003. Published 23 October 2003.
Managing Risk to Minimize Crop Loss: Introduction to the Symposium Proceedings
Authors: Turechek William W.
Published: May 2008

In these proceedings, approaches to assessing, predicting and managing risk in production agriculture and international trade are addressed. This set of papers follows a symposium organized by the Plant Disease Losses and Regulatory Committees of the American Phytopathological Society for its 2002 Annual Meeting held in Milwaukee, WI.

Published 13 November 2003.
Transgenic Papaya: A Case for Managing Risks of Papaya ringspot virus in Hawaii
Authors: Gonsalves Dennis , Ferreira Steve
Published: May 2008

In May 1992, Papaya ringspot virus (PRSV) was detected in the Puna district of Hawaii Island, the main papaya growing region of the state of Hawaii. By 1994 Hawaii's papaya industry was facing devastating damage from PRSV. Efforts to develop resistant transgenic papaya were started in the mid 1980s and a resistant line was identified in 1991. Two cultivars were developed from this line and were commercialized in 1998. Rainbow, an F1 hybrid from a cross of the transgenic SunUp, and nontransgenic Kapoho are now widely planted and have helped save the papaya industry. In addition, PRSV inocula in Puna were greatly reduced as abandoned infected fields were replanted with transgenic papaya. These conditions have allowed growers to continue the production of nontransgenic Kapoho in Puna to keep the Japanese market supplied, since transgenic papaya is not yet deregulated in that country.

Accepted for publication 5 November 2003. Published 13 November 2003.
Analyzing Positive Finds with Explicit Uncertainty
Authors: Brown Lawrence G.
Published: May 2008

Regulatory realities, culture, and politics impinge on scientifically based policy recommendations. An appreciation of the regulatory framework that creates policy recommendations helps in understanding why it is important to state the confidence intervals, i.e., to state explicitly the uncertainty of each recommendation. Part of the proceedings of “Managing Risk to Minimize Crop Loss,” a symposium organized by the Plant Disease Losses and Regulatory Committees of APS.

Accepted for publication 11 April 2003. Published 13 November 2003.
Resistance to Take-all is Not Expressed in Wheat-Alien Chromosome Addition and Substitution Lines
Authors: Kim Yong-Ki , Friebe Bernd , Bockus William W.
Published: May 2008

Take-all is regarded as the most damaging root disease wheat and is widely distributed worldwide. In spite of its importance, little progress has been made in breeding for resistance. In this study, a greenhouse bioassay was used to establish that transfer of take-all resistance from H. vulgare, H. chilense, or H. villosa to wheat may not be easily accomplished.

Accepted for publication 6 October 2003. Published 24 November 2003.
Sensitivity of Newly Identified Clades in the Sooty Blotch and Flyspeck Complex on Apple to Thiophanate-methyl and Ziram
Authors: Tarnowski Tara , Batzer Jean , Gleason Mark , Helland Sara , Dixon Phillip
Published: May 2008

Sensitivity to the fungicides thiophanate-methyl and ziram was characterized for newly identified clades in the sooty blotch and flyspeck (SBFS) disease complex. Isolates obtained from apple orchards in Illinois, Iowa, Missouri, and Wisconsin were previously grouped into clades based on parsimony analysis of the internal transcriber spacer (ITS) and large subunit (LSU) regions of rDNA. Two isolates from each of eight clades were cultured on water agar amended with a range of fungicide concentrations. Radial growth of colonies was measured after incubation for 21 days at 25°C. Fungicide sensitivity (ED50) did not differ significantly (P = 0.05) between isolates within a clade, but several clades differed significantly. There was a greater variability among clades for sensitivity to thiophanate-methyl than for ziram. Significant differences in fungicide sensitivity among, but not within, clades provide evidence that these clades differ physiologically. Understanding differences in fungicide sensitivity among SBFS clades could have practical implications for improved management of SBFS.

Accepted for publication 12 November 2003. Published 9 December 2003.
Mango Dieback and Gummosis in Sindh, Pakistan Caused by Lasiodiplodia theobromae
Authors: Khanzada Muhammad Ali , Lodhi Abdul Mubeen , Shahzad Saleem
Published: May 2008

Diagnosis of dieback and gummosis (caused by Lasiodiplodia theobromae (Pat.)) on mango in Sindh, Pakistan is described, including: taxonomy; symptoms and signs; host range; geographical distribution; pathogen isolation, identification, and storage; and pathogenicity tests.

Accepted for publication 16 January 2004. Published 2 March 2004.
Evaluation of Soybean Differentials for Their Interaction with Phytophthora sojae
Authors: Dorrance A. E. , Jia H. , Abney T. S.
Published: May 2008

Soybean lines, each containing a different resistance gene (Rps), are used as differentials to characterize isolates of Phytophthora sojae as physiologic races. Surveys in different soybean production regions have used various sets of soybean differentials thought to carry the same Rps genes. In some instances, isolates of P. sojae have been reported to have different reactions when evaluated in labs using different sets of differentials that were believed to have the same Rps gene. The objective of this study was to compare the consistency of racial classification when three different sets of soybean differentials were challenged with a common set of five races of P. sojae from Ohio and Indiana. Three soybean differential sets (USDA Soybean Germplasm Collection, The Ohio State University, and USDA-ARS Purdue University) were challenged with P. sojae using the hypocotyl inoculation test at OSU and USDA-ARS Purdue. Isolates of races 1, 3, 4, 7, and 25 from Ohio and Indiana had the same reaction on all three sets of soybean differentials for Rps1b, Rps1c, Rps1k, Rps3a, Rps3b, Rps3c, Rps6, Rps7, and on differentials Harlon, Harosoy 12xx, L59-731, and Union for Rps1a. L88-8470 used as a differential for Rps1a and L93-3312 used for Rps1d did not have the expected response. Isolates of races 4 and 25 from Ohio and Indiana responded differently on differentials with the Rps2 gene because this gene was not used previously to characterize races of P. sojae. A similar reaction occurred when differentials with Rps4 and Rps5 were inoculated with isolates of races 1 and 7, respectively. A standardized set of soybean differentials, corresponding to different maturity groups, for thirteen of the fourteen Rps genes is recommended.

Accepted for publication 5 February 2004. Published 9 March 2004.
Surveying For and Eradicating Phytophthora ramorum in Agricultural Commodities
Authors: Osterbauer Nancy K. , Griesbach John A. , Hedberg Jan
Published: May 2008

Since 2001, Oregon nurseries, Christmas tree plantations, and other sites have been surveyed for the federally regulated pathogen Phytophthora ramorum. Host plants at each site were visually surveyed for disease symptoms and symptomatic tissues tested in the laboratory by isolation onto a selective medium and by a polymerase chain reaction (PCR) assay. In 2002 and 2003, we detected PCRpositive plants that later proved to be infected with another Phytophthora, suggesting there are limitations to the PCR assay tested. In 2003, P. ramorum was detected for the first time in Viburnum, Pieris, Rhododendron, and Camellia plants in six nurseries. All infected and neighboring plant materials were destroyed by incineration and the nurseries and surrounding environs subsequently surveyed for the pathogen. Phytophthora ramorum was not detected, indicating the pathogen was successfully eradicated.

Accepted for publication 10 February 2004. Published 9 March 2004.
First Report of Leptographium abietinum Associated with Blue Stain on Declining Western Siberian Larch in Alaska
Authors: McBeath Jenifer H. , Cheng M. , Gay P. , Ma M. , Alden John
Published: May 2008

During 2002, dead tops, branch dieback, and resinosis were observed in Interior Alaska on stands of 20-year-old western Siberian larch (Larix sukaczewii), a fast-growing tree species introduced to Alaska in 1949. In this study, a Leptographium species was consistently recovered. This is believed to be the first report of blue stain caused by Leptographium in western Siberian larch in Alaska. No other Leptographium species have been found on western Siberian larch in Alaska.

Accepted for publication 16 March 2004. Published 23 March 2004.
Efficacy of Foliar Applications of Particle Films and Genotype for Managing Thrips, Diseases, and Aflatoxin in Peanut
Authors: Wilson J. P. , Holbrook C. C. , Mandal B. , Rowland D. L. , Wells M. L. , Wilson D. M.
Published: May 2008

The kaolin-based particle film Surround has been shown to suppress various insect pests and foliar diseases while reducing canopy temperature and improving water use efficiency in certain agricultural production systems. The usefulness of Surround was examined against important production constraints in peanut, including tomato spotted wilt, leaf spots, and aflatoxin contamination. Field experiments were conducted during 2001 using multi-varietal trials with or without spray treatment of Surround (75 lbs/acre) + NuFilm-17 (8 oz/acre). The effects of Surround application were evaluated for control of thrips and tomato spotted wilt on genotypes Georgia Green, C11-2-39, C34-24, and Sunoleic 97R; for control of leaf spots on AgraTech 201, GK 7 High Oleic, and C-99R; and for control of aflatoxin contamination on Aspergillus-inoculated plots of genotypes Georgia Green, AgraTech 201, and GK 7 High Oleic. In these experiments, Surround applications had little or no effect on thrips populations, tomato spotted wilt severity and incidence, leaf spot severity, drought stress, aflatoxin contamination, chlorophyll content, specific leaf area, and pod yield. In all experiments, host genotype effects were more effective in reducing disease and increasing yield than was Surround protection. Although foliar applications of particle films may be useful for producing certain vegetables and fruits, its benefits for addressing peanut production constraints are limited.

Accepted for publication 7 April 2004. Published 19 April 2004.
First Report of Powdery Mildew of Onion (Allium cepa) Caused by Leveillula taurica in the Pacific Northwest
Authors: du Toit Lindsey J. , Glawe Dean A. , Pelter Gary Q.
Published: May 2008

A powdery mildew disease of onion has been observed infrequently in the Columbia Basin of Washington State since 1996, but this is the first published report of this disease in the Pacific Northwest. The causal agent was determined to be Leveillula taurica (Lév.) G. Arnaud.

Accepted for publication 29 October 2004. Published 29 November 2004.
Spread of Wheat Curl Mite and Wheat Streak Mosaic Virus is Influenced by Volunteer Wheat Control Methods
Authors: Thomas J. A. , Hein G. L. , Lyon D. J.
Published: May 2008

Wheat streak mosaic virus is the most damaging disease in winter wheat in the western Great Plains. The wheat curl mite is the vector of this virus and utilizes volunteer wheat as a “green bridge” to over-summer and re-infest fall planted winter wheat. This study demonstrates the effect of tillage and glyphosate control of volunteer wheat on mite movement and subsequent virus infection. Small mite populations (1 to 2 mites per tiller) caused high infection rates in winter wheat. Both tillage and glyphosate were effective at reducing mite populations on volunteer wheat, but tillage resulted in more rapid reduction of mite populations. If volunteer wheat is to be controlled close to planting time, tillage is the best choice for rapid control of mite populations when warm dry weather conditions exist.

Accepted for publication 21 October 2004. Published 6 December 2004.
First Report of Hibiscus latent Fort Pierce virus in New Mexico
Authors: Allen Jean E. , Kamenova Ivanka , Adkins Scott , Hanson Stephen F.
Published: May 2008

During the summer of 2003, foliar symptoms including chlorotic spots and chlorotic mottling were observed on Hibiscus rosa-sinensis and H. syriacus plants in and around Las Cruces, NM. Detection of Hibiscus latent Fort Pierce virus (HLFPV) in numerous samples suggests that it may be widely distributed in New Mexico, as is the case in Florida and Thailand. Movement of ornamental plants could increase the geographic distribution of HLFPV. This represents the first report of HLFPV in the western United States.

Accepted for publication 22 November 2004. Published 5 January 2005.
Efficacy of Azoxystrobin, Pyraclostrobin, Potassium Phosphite, and Mefenoxam for Control of Strawberry Leather Rot Caused by Phytophthora cactorum
Authors: Rebollar-Alviter A. , Ellis M. A.
Published: May 2008

Efficacy of azoxystrobin, pyraclostrobin, mefenoxam, and potassium phosphite for control of strawberry leather rot, caused by Phytophthora cactorum, was evaluated on a commercial farm. Foliar sprays of azoxystrobin, pyraclostrobin, and potassium phosphite were applied weekly from bloom through harvest and mefenoxam was applied twice as a soil drench at early plant growth and at fruit set. All fungicide treatments had significantly less leather rot than the untreated control and there were no significant differences in leather rot incidence between any fungicide treatment during both years of testing. Mefenoxam (Ridomil Gold) and potassium phosphite (ProPhyt) are currently registered for control of strawberry leather rot in the U.S. Although they are registered for use on strawberry, leather rot is not on the azoxystrobin (Abound) or pyraclostrobin (Cabrio) labels. Results from these studies indicate that both of these strobilurin fungicides provide excellent control of strawberry leather rot.

Accepted for publication 28 November 2004. Published 7 January 2005.
First Report of Association Between Delphinium and Peziza repanda
Authors: Wegulo Stephen N. , Vilchez Miguel , Menge John
Published: May 2008

Delphinium is a popular field-grown cut flower. In February 2004, a grower expressed concern about an abundant fungal growth. The fungus was identified as Peziza repanda. This fungus is common in nurseries that raise plugs on container media amended with wood material. Nursery growers should be aware of the potential for contamination of these media with spores of fungi commonly associated with wood. This report documents the first observation of an association between delphinium and an ascomycetous cup fungus.

Accepted for publication 7 December 2004. Published 14 February 2005.
Silicon is Deposited in Leaves of New Guinea Impatiens
Authors: Frantz Jonathan M. , Pitchay Dharmalingam D. S. , Locke James C. , Horst Leona E. , Krause Charles R.
Published: May 2008

Although silicon (Si) is not considered to be an essential plant nutrient because most plants can complete their life cycle without it, many investigators have shown a positive growth effect, such as increased disease resistance, if Si is present. The effect of Si on many ornamental and greenhouse crop species has not been extensively studied. In greenhouse culture, plants are not exposed to Si from mineral soil, so Si should be added to the fertilizer solutions with mineral soil or soil amendments if there are benefits of Si. The initial step in determining potential benefits of Si requires the documentation of Si uptake and localization within the plant. We grew New Guinea impatiens for four weeks and exposed them to 2.0 mM Si in the form of K2SiO4. Using scanning electron microscopy and energy dispersive X-ray analysis, we detected Si deposits on the leaf margins in unique, Si-filled cells, primarily near hydathodes. We did not detect Si in the xylem. This report is the first documentation of Si uptake or accumulation in any species of the Balsaminaceae family.

Accepted for publication 12 January 2005. Published 17 February 2005.
Evaluation of Fungicides for Control of Pythium Blight in Overseeded Turfgrasses Using a Simple Field Inoculation Technique
Authors: Stiles Carol M. , Datnoff Lawrence E. , Cisar John L.
Published: May 2008

A simple inoculation technique, which uses small plastic boxes as field inoculation chambers, was developed to enhance disease development in turfgrass inoculated with Pythium aphanidermatum. When temperatures were favorable and relative humidity was high under the plastic boxes, disease severity attained 70 to 90% in untreated controls. This technique was used to screen several fungicides for efficacy in controlling Pythium blight over four years. Preventative treatments of azoxystrobin, mefenoxam, and fosetyl-Al were highly effective in controlling Pythium blight even under very high disease pressure. Curatively, mefenoxam and azoxystrobin also controlled Pythium blight, if applied as soon as symptoms (≤ 5% disease severity) were detected.

Accepted for publication 12 March 2005. Published 30 March 2005.
Effect of Nitrogen Fertilization and Seed Contamination on Epiphytic Populations of Xanthomonas axonopodis pv. allii and Development of Xanthomonas Leaf Blight of Onion
Authors: Gent David H. , Schwartz Howard F.
Published: May 2008

Xanthomonas leaf blight of onion, caused by Xanthomonas axonopodis pv. allii, is a yield-limiting disease in Colorado, for which few effective management strategies are available. The effects of rates of nitrogen fertilization and levels of seed contamination by X. axonopodis pv. allii on epiphytic populations of the pathogen and subsequent disease development were determined in field studies over two years. Epiphytic populations of a rifampicin-resistant mutant were quantified from bulked, asymptomatic leaf tissue using a leaf wash assay. There was no significant relationship between nitrogen fertilization treatment and epiphytic population development, but excessive nitrogen (> 200 kg/ha) fertilization increased disease severity 27 to 50% compared with non-fertilized and low (112 kg/ha) nitrogen fertilizer treatments in 2004. Seed inoculated with various levels of X. axonopodis pv. allii did not result in persistent epiphytic populations of the bacterium or development of symptoms, even at 107 CFU/g of seed. The results of these studies suggest moderate rates of nitrogen fertilization may reduce severity of Xanthomonas leaf blight compared to higher rates, and that seed contamination by X. axonopodis pv. allii may be of limited importance for disease development under the semi-arid conditions of furrow-irrigated onion production in Colorado.

Accepted for publication 13 March 2005. Published 31 March 2005.
First Report of Raspberry bushy dwarf virus in Ohio
Authors: Ellis M. A. , Kraus J. , Martin R. R. , Wright S. R.
Published: May 2008

Over the past 10 years, several commercial producers of black raspberry in Ohio have experienced a decline in plant vigor and survival in their plantings. In 2004, a survey of several black and red raspberry plantings in Ohio was conducted to determine if viruses were present. Of the 115 samples taken in the survey, Raspberry bushy dwarf (RBDV), Tomato ringspot (ToRSV), and Tobacco ringspot virus (TRSV) were detected in 21, 5, and 2, respectively. This is the first report of RBDV in Ohio.

Accepted for publication 27 April 2005. Published 10 May 2005.
Comparing Image Format and Resolution for Assessment of Foliar Diseases of Wheat
Authors: Steddom Karl , McMullen Marcia , Schatz Blain , Rush Charles M.
Published: May 2008

For image analysis to be a useful method for assessment of foliar diseases, it must be robust with respect to changes in image resolution. In addition, the use of common compression methods such as JPEG allows for the use of low-cost digital cameras and reduces the storage requirements of the imagery. We have investigated the effect of image resolution and format on lesion area quantification with image analysis. Wheat leaves with various levels of rust and tan-spot were scanned on a flatbed scanner as TIFF images with a resolution of 8.4 million pixels per image. These images were then progressively reduced in resolution down to 858 pixels per image. The TIFF images were then converted to JPEG images with quality settings of 100, 75, 50, and 25 percent. The percentage of necrotic leaf area was then measured for each image, and correlated with the percentage of necrotic leaf area of the original 8.4 million pixel TIFF images. Image format had little effect on the results and image resolution did not affect results until the image resolution had dropped below the level at which it was difficult to discern lesions by eye. This suggests that low-resolution digital cameras with high JPEG compression levels are suitable for plant disease measurement using image analysis.

Accepted for publication 21 April 2005. Published 16 May 2005.
Incidence of Meloidogyne incognita and Development of Resistant Soybean Germplasm in Illinois
Authors: Allen J. B. , Bond J. P. , Schmidt M. E.
Published: May 2008

In 2002-2003, a nematode survey was conducted in the southernmost counties of Illinois. Species in eight nematode genera were detected in the survey with four genera having species considered to be important soybean pathogens. Populations of Meloidogyne incognita were detected in 6% of all fields surveyed in southern Illinois. Elite breeding lines and cultivars were evaluated for resistance to gall formation and reproduction by the nematode. Resistance was identified in several soybean genotypes.

Accepted for publication 27 April 2005. Published 6 June 2005.
First Report of Powdery Mildew of Mahonia aquifolium (Pursh.) Nutt. Caused by Erysiphe (Microsphaera) berberidis (DC.) Lév in Canada
Authors: Zhao Shiguang , Shamoun Simon F.
Published: May 2008

Mahonia aquifolium (Tall Oregon Grape) is a plant native to British Columbia and the coastal Pacific Northwest of the USA. The first discovery of powdery mildew of Mahonia aquifolium in the USA was reported in Washington State in 2003. In Canada, powdery mildew of Oregon grape was discovered in the early summer of 2004 in Victoria, BC. To our knowledge, this is the first record of powdery mildew caused by E. berberidis on Oregon grape in Canada.

Accepted for publication 15 May 2005. Published 21 June 2005.
Determining the Efficacy of Disease Management Products in Organically-Produced Tomatoes
Authors: Wszelaki Annette L. , Miller Sally A.
Published: May 2008

Sixteen disease control products or product combinations used in organic production systems were tested for efficacy against tomato diseases. Disease pressure was low in 2002, and no treatment significantly reduced disease relative to the control. In 2003, early blight and Septoria leaf spot developed late in the season, and Bordeaux mixture, copper hydroxide, garlic and neem oils, seaweed extract, and Serenade reduced disease development compared to the control. Plots treated with Sonata yielded the most marketable fruit.

Accepted for publication 18 May 2005. Published 13 July 2005.
Differentiation of Isolates of Glomerella cingulata and Colletotrichum spp. Associated with Glomerella Leaf Spot and Bitter Rot of Apples Using Growth Rate, Response to Temperature, and Benomyl Sensitivity
Authors: González Eugenia , Sutton Turner B.
Published: May 2008

Cultural characteristics were investigated as a way to distinguish isolates of Glomerella cingulata and Colletotrichum spp. associated with Glomerella leaf spot and bitter rot of apples from those that cause only bitter rot. The growth rate, response to temperature, and benomyl sensitivity of 27 isolates of Glomerella cingulata, 12 isolates of Colletotrichum gloeosporioides, and 7 isolates of C. acutatum, collected from apple orchards located in the U.S. and Brazil and previously characterized based on morphology, vegetative compatibility, and mitochondrial DNA (mtDNA) haplotypes, were determined. These isolates represent the genetic and molecular diversity within isolates of C. gloeosporioides, C. acutatum, and G. cingulata from apples found in a previous study. Slower growth, lower optimum growth temperature, and less sensitivity to benomyl distinguished isolates of C. acutatum from isolates of G. cingulata and C. gloeosporioides. However, growth rate and benomyl sensitivity were not useful for distinguishing between G. cingulata and C. gloeosporioides or differentiating isolates of G. cingulata that cause leaf spot and bitter rot from those that only cause bitter rot.

Accepted for publication 17 May 2005. Published 19 July 2005.
A Temperature-Controlled Water Bath Method for Evaluating Soybean Reaction to Sudden Death Syndrome (SDS)
Authors: Hashmi R. Y. , Bond J. P. , Schmidt M. E. , Klein J. H.
Published: May 2008

Many greenhouse screening methods have been tested to evaluate soybean genotypes for reaction to sudden death syndrome (SDS) caused by Fusarium solani f. sp. glycines. These methods generally have proven disappointing in that results are not consistent among methods or do not correlate with field reaction. In the present study, SDS foliar symptom severity among 24 soybean genotypes was compared using three inoculation methods in the greenhouse. The pathogen inoculum was either mixed (seedbed mixing) or layered (seedbed layering) in the soil medium prior to planting seed and then kept on a greenhouse bench or the inoculum was layered in the soil medium and kept in a temperature control water bath. The water bath method was similar to the layering method with the addition of precise temperature control. The water bath method was superior to the other methods in consistency of SDS symptoms among genotypes among trials and in agreement with SDS field reaction. When disease severity data obtained in the greenhouse were regressed with foliar disease data obtained in field trials, R2 values were 0.56, 0.60, and 0.81 for the seedbed mixing, seedbed layering, and water bath methodS, respectively. The improved ability to predict field response using the water bath method likely results from precise control of the temperature in the rhizosphere. The water bath method described herein will increase the efficiency of selection for highly adapted SDS resistant cultivars by reducing the number of genotypes that must be evaluated under field conditions.

Accepted for publication 2 August 2005. Published 6 September 2005.
First Report of Phragmidium violaceum Infecting Himalaya and Evergreen Blackberries in North America
Authors: Osterbauer N. , Trippe A. , French K. , Butler T. , Aime M. C. , McKemy J. , Bruckart W. L. , Peerbolt T. , Kaufman D.
Published: May 2008

Phragmidium violaceum occurs on several species of Rubus, including R. armeniacus, R. fruticosus agg., and R. laciniatus, in Europe, South Africa, Iran, and Iraq, and has been introduced as a biological control agent for invasive blackberries in Australia, New Zealand, and Chile. To our knowledge, this is the first official report of P. violaceum infecting Himalaya and evergreen blackberries in North America.

Accepted for publication 16 September 2005. Published 23 September 2005.
First Report of Powdery Mildew on Caragana arborescens and Caragana grandiflora in Alaska caused by Microsphaera (Erysiphe) palczewskii
Authors: Glawe Dean A. , Laursen Gary A.
Published: May 2008

During August 2004, the authors surveyed sites in and near Fairbanks, AK for powdery mildew diseases and found a powdery mildew previously unreported in Alaska on two specimen plants of the introduced ornamental species Caragana arborescens Lam. (Siberian pea tree) and C. grandiflora DC. The causal agent was determined to be Microsphaera palczewskii Jacz. This report provides the first documentation of M palczewskii in AK and includes information on the morphology and taxonomy of this species.

Accepted for publication 27 September 2005. Published 17 October 2005.
First Report of Powdery Mildew of Scabiosa columbaria (Dove Pincushions) Caused by Erysiphe knautiae in North America
Authors: Glawe Dean A. , Grove Gary G.
Published: May 2008

Scabiosa columbaria L. (dove pincushions) is a perennial species introduced into North America, where it is grown as an ornamental landscape plant. Little information is available on pathogens attacking it in North America. Recently, the authors encountered a powdery mildew fungus on this host species in Washington and determined it to be Erysiphe knautiae Duby. This report describes the disease as well as diagnostic features and taxonomy of the causal agent.

Accepted for publication 11 October 2005. Published 24 October 2005.
Alternatives to Methyl Bromide: A Florida Perspective
Authors: Rosskopf Erin N. , Chellemi Daniel O. , Kokalis-Burelle Nancy , Church Gregory T.
Published: May 2008

Methyl bromide is a soil fumigant used to control soilborne fungi, nematodes, and weeds in a wide range of agricultural, horticultural, and ornamental cropping systems. The Montreal Protocol of 1987 called for the phase-out of methyl bromide due to its ability to deplete atmospheric ozone, thus disrupting the UV protective ozone layer. This article reviews the current status of the on-going methyl bromide phase-out from the perspective of agriculture in Florida.

Accepted for publication 27 September 2005. Published 27 October 2005.
Evaluating the Efficacy of Commercial Products for Management of Bacterial Leaf Spot on Lettuce
Authors: Bull Carolee T. , Koike Steve T.
Published: May 2008

The efficacy of Serenade, Maneb, Cuprofix, and mixtures of these products were evaluated for efficacy in reducing disease incidence and severity of bacterial leaf spot of lettuce caused by Xanthomonas campestris pv. vitians in six trials at two locations between 2001 and 2003. Additionally, Messenger, elemental copper, Quadris, and Actigard were evaluated in at least two of these trials. Mixtures of Serenade and Cuprofix reduced disease incidence in three of six experiments and reduced disease severity in a fourth experiment. Treatment with the Maneb and Cuprofix mixture was less effective but resulted in significantly less disease and lower severity in single experiments. These results indicate that a mixture of Serenade and Cuprofix may be a useful addition to an integrated bacterial leaf spot disease management strategy but this treatment may be too variable to justify it as a stand-alone treatment.

Accepted for publication 21 October 2005. Published 21 November 2005.
Integrated Management of Angular Leaf Spot (Phaeoisariopsis griseola (Sacc.) Ferr.) on Snap Beans in Ontario
Authors: Celetti Michael J. , Melzer Melody S. , Boland Greg J.
Published: May 2008

Angular leaf spot (ALS) caused by the fungus Phaeoisariopsis griseola (Sacc.) Ferr. was first observed and confirmed on snap beans growing in three commercial fields in southern Ontario during the 2000 growing season. The potential impact of this disease on the bean industry in Ontario is not known but this disease is severe in many other regions. The objective of this study was to develop a disease management strategy for ALS in Ontario by investigating the survival of P. griseola in Ontario, and assessing the influence of bean varieties and fungicides on disease development. P. griseola survived at least one winter on crop debris in Ontario and survived better on the soil surface in comparison to burial in soil at depths of 5 or 25 cm. Fifteen snap bean varieties were compared for susceptibility to ALS in a growth room, and nine varieties were compared in a naturally-infested field from 2001-2003. Most varieties reacted similarly to P. griseola in both environments. For example, the varieties Carlo, Storm, and Bush Blue Lake 47 were least susceptible whereas Gold Rush was most susceptible in field and growth room experiments. Boscalid, pyraclostrobin, pyramethanil, vinclozolin, and thiophanate-methyl were tested for effectiveness in managing ALS under field conditions. Overall, pyraclostrobin was most effective. Results indicate that an effective disease management strategy for ALS in snap bean in Ontario should include burying infested plant debris through deep plowing, crop rotation for two years, growing the least susceptible varieties, and applying a registered effective fungicide.

Accepted for publication 13 October 2005. Published 29 November 2005.
Evaluation of Soybean Germplasm for Resistance to Phakopsora pachyrhizi
Authors: Miles M. R. , Frederick R. D. , Hartman G. L.
Published: May 2008

Phakopsora pachyrhizi, the causal fungus of soybean rust, was discovered in the continental U.S. in November 2004. The presence of this disease in the U.S. may have an impact on soybean (Glycine max) production, as the current commercial varieties are considered to be susceptible, and the use of one or more applications of fungicides will add additional costs to production. One objective of the USDA-ARS research on soybean rust is to identify soybean germplasm with resistance to the disease. There are over 16,000 soybean accessions in the USDA Germplasm Collection located at the University of Illinois. These accessions were evaluated in a two-tiered inoculation program using a mixture of four P. pachyrhizi isolates in Biosafety Level 3 containment greenhouses the FDWSRU. In the first round of evaluations, 16,595 accessions were rated for rust severity. Of these, 3,215 accessions, based on low visual rust severity or the presence of a red-brown reaction, were selected for a second round of evaluation. After the second round of replicated evaluations of the 3,215 accessions, 805 were selected for further evaluation, again based on low mean visual severity or the presence of a red-brown reaction. Some of these selected accessions have the potential to provide soybean rust resistance genes that may be useful for incorporation into commercial soybean cultivars.

Accepted for publication 9 November 2005. Published 4 January 2006.
First Report of Powdery Mildew of Gaillardia × grandiflora (Blanket Flower) Caused by Leveillula taurica in North America
Authors: Glawe Dean A. , Grove Gary G. , Nelson Mark
Published: May 2008

During recent surveys of fieldgrown Gaillardia × grandiflora (Blanket flower) in Yakima Co., WA, a powdery mildew disease was observed on the cv. ‘Baby Cole.’ This report documents the occurrence of the powdery mildew fungus in question (Leveillula taurica (Lév.) G. Arnaud) on Gaillardia × grandiflora and provides information on disease symptomatology as well as features distinguishing this fungus from other powdery mildew pathogens of Gaillardia in North America.

Accepted for publication 8 December 2005. Published 12 January 2006.