scholarly journals Identification of Rhizoctonia solani AG-UNK from Rice and Rice Fields in Texas as AG-11

Plant Disease ◽  
1999 ◽  
Vol 83 (9) ◽  
pp. 880-880 ◽  
Author(s):  
R. K. Jones ◽  
D. E. Carling
Keyword(s):  
Rhizoctonia Solani ◽  
Gulf Coast ◽  
The United States ◽  
Field Trials ◽  
Causal Agent ◽  
Rice Fields ◽  
Low Frequencies ◽  
Late Season ◽  
Significant Yield ◽  
Stem Lesions

A survey of Texas rice fields in 1984 and 1985 yielded collections of Rhizoctonia solani AG-1 IA (causal agent of sheath blight of rice), R. oryzae (causal agent of sheath spot of rice), and a collection of eight multinucleate Rhizoctonia solani-like isolates that would interanastomose, but not anastomose, with tester isolates of AG-1 through AG-8 (representing those available at that time). In 1985, the isolates were characterized as R. solani AG-UNK (2). Isolates were recovered as atypical sclerotia from elutriated field soils in rice-soybean and rice-fallow rotations. Isolates also were recovered from late-season stem lesions nearly identical to those associated with sheath spot disease and from rice residues at locations throughout the upper Gulf Coast of Texas but at extremely low frequencies compared with recovery of R. solani AG-1 IA and R. oryzae. Teleomorphs of R. solani AG-UNK were observed during middle to late season on rice sheaths and matched descriptions of Thanatephorus cucumeris. Isolates were pathogenic on rice and soybean foliage in greenhouse trials but caused no significant yield losses when inoculated on adult rice plants (50 days after emergence) in field trials (2). Isolates exhibited mean hyphal diameters of 5.1 μm, averaged 8.3 nuclei per penultimate cell, grew 0.53 mm/h at 28°C on potato dextrose agar, and were negative in phenol tests (2). From samples maintained in storage during the past 15 years, the isolates have now been identified as AG-11 based on positive anastomosis with tester strains of AG-11 (1). This report records the occurrence of AG-11 in Texas, establishes the identity of the AG-UNK group, and expands the known geographic range of AG-11 in the United States. References: (1) D. E. Carling et al. Phytopathology 84:1387, 1994. (2) R. K. Jones and S. B. Belmar. Plant Dis. 73:1004, 1989.

scholarly journals First Report of Anthracnose of Lentil Incited by Colletotrichum truncatum in Bulgaria

Plant Disease ◽  
1998 ◽  
Vol 82 (1) ◽  
pp. 128-128 ◽  
Author(s):  
W. J. Kaiser ◽  
M. Mihov ◽  
F. J. Muehlbauer ◽  
R. M. Hannan
Keyword(s):  
Severe Infection ◽  
Plant Introduction ◽  
The United States ◽  
Field Trials ◽  
Colletotrichum Truncatum ◽  
Low Frequencies ◽  
First Report ◽  
Pure Cultures ◽  
Pathogenicity Tests ◽  
Stem Lesions

In June 1992 and 1995, anthracnose of lentil (Lens culinaris Medik.) incited by Colletotrichum truncatum (Schwein.) Andrus & W. D. Moore was widespread in field trials at the Institute for Wheat and Sunflower ‘Dobroudja’ near General Toshevo in northeastern Bulgaria. Lesions on the leaves, stems, and pods were usually white to grayish on younger plants, often turning brown as plants matured. Severe infection usually resulted in dieback and/or death of plants. Acervuli containing spores and dark setae were observed within lesions, and conidia from the acervuli produced pure cultures of C. truncatum. Conidia were hyaline, onecelled, falcate to nearly straight with a prominent clear area in the center of highly granular cytoplasm, and measured 17.6 to 19.8 × 4.4 μm. C. truncatum was seed-borne in naturally infected lentil cv. Tadjikskaya 95 at low frequencies (<2%). Koch's postulates were fulfilled by inoculating the foliage of lentil cvs. Brewer and Pardina and reisolating the fungus from stem and petiole lesions. In pathogenicity tests, three isolates of C. truncatum from the foliage and seeds of lentil caused severe symptoms on inoculated lentil cvs. Brewer and Pardina, similar to those observed on diseased lentils in Bulgaria. The fungus also caused moderate symptoms on inoculated faba bean (Vicia faba L.) and pea (Pisum sativum L.), and light symptoms on inoculated chickpea (Cicer arietinum L.). In 1995, 258 USDA Plant Introduction (PI) accessions from the USDA lentil core collection were screened in replicated trials in northeastern Bulgaria and disease symptoms were observed in >90% of the lines. Anthracnose severity ranged from light to severe. A few accessions appeared to have acceptable levels of resistance to the disease. These included accessions from Iran (PI 431714 and 431717) and Spain (PI 533693). Also that year, C. truncatum was isolated from stem lesions of naturally infected bitter vetch (Vicia ervilia (L.) Willd.) at the Institute for Wheat and Sunflower ‘Dobroudja’. The disease in Bulgaria appears to be identical to one causing anthracnose of lentil in Canada (1) and the United States (2). This is the first report of C. truncatum causing anthracnose of lentil in Bulgaria. References: (1) R. A. A. Morrall. Plant Dis. 72:994, 1988. (2) J. R. Venette et al. Plant Dis. 78:1216, 1994.

scholarly journals Control of Rhizoctonia solani in Sugar Beet and Effect of Fungicide Application and Plant Cultivar on Inoculum Potential in the Soil

Plant Disease ◽  
2017 ◽  
Vol 101 (6) ◽  
pp. 941-947 ◽  
Author(s):  
Anika Bartholomäus ◽  
Stefan Mittler ◽  
Bernward Märländer ◽  
Mark Varrelmann
Keyword(s):  
Sugar Beet ◽  
Rhizoctonia Solani ◽  
Natural Infection ◽  
Resistance Management ◽  
The United States ◽  
Similar Efficacy ◽  
Field Trials ◽  
Crown Rot ◽  
Inoculum Potential ◽  
Fungicide Application

Rhizoctonia solani (AG 2-2 IIIB) is the causal agent of Rhizoctonia root and crown rot, a disease that causes severe economic problems in sugar beet growing areas worldwide. In the United States, azoxystrobin is the most important active ingredient for fungicidal control of R. solani in sugar beet, showing efficacy superior to other substances. First reports on resistance development in R. solani, however, underline the importance of a careful fungicide resistance management. For this reason, the efficacy of a new fungicide mixture of azoxystrobin and difenoconazole was compared with a fungicide containing only azoxystrobin. Field trials were carried out under natural infection conditions as well as with inoculation in the years 2012, 2013, and 2014. Evaluation of the disease severity and the obtained white sugar yield of different sugar beet cultivars demonstrated that both fungicide treatments possess a similar efficacy, reducing the diseased beet surface by up to 78% and preventing yield losses. Additionally, a real-time PCR assay, based on DNA extracts from representative soil samples (250 g), was used to directly determine the effect of chemical treatment and plant cultivar on the soil-borne inoculum. Fungicide application significantly reduced the concentration of soil-borne inoculum by up to 97%. Furthermore, the results demonstrated that the cultivation of a susceptible cultivar significantly increases the concentration of R. solani in the soil by a factor of 200. In conclusion, the study implies that only a combination of resistant cultivar and fungicide application can prevent an accumulation of R. solani inoculum under conducive conditions in infested fields.

scholarly journals Evaluation of Quinoxyfen Resistance of Erysiphe necator (Grape Powdery Mildew) in a Single Virginia Vineyard

Plant Disease ◽  
2018 ◽  
Vol 102 (12) ◽  
pp. 2586-2591 ◽  
Author(s):  
Xuewen Feng ◽  
Mizuho Nita ◽  
Anton B. Baudoin
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Disease Control ◽  
Low Dose ◽  
Disease Incidence ◽  
The United States ◽  
Field Trials ◽  
Erysiphe Necator ◽  
Late Season ◽  
Grape Powdery Mildew

The protectant fungicide quinoxyfen has been used against grape powdery mildew (Erysiphe necator) in the United States since 2003. In 2013, isolates of grape powdery mildew with reduced quinoxyfen sensitivity (here designated as quinoxyfen lab resistance or QLR) were detected in a single vineyard in western Virginia, USA. Field trials were conducted in 2014, 2015, and 2016 at the affected vineyard to determine to what extent quinoxyfen might still contribute to disease control. Powdery mildew control by quinoxyfen was similar to, or only slightly less than, that provided by myclobutanil and boscalid in all three years. In 2016, early- versus late-season applications of quinoxyfen were compared to test the hypothesis that early-season applications were more effective, but differences were small. A treatment with two early quinoxyfen applications, at bloom and 2 weeks later, followed by a myclobutanil-boscalid plus a low dose of sulfur rotation provided slightly better control of foliar disease incidence than treatments containing four quinoxyfen applications or two midseason or two late quinoxyfen applications supplemented by myclobutanil and boscalid applications; severity differences were small and nonsignificant. Metrafenone and benzovindiflupyr generally provided excellent powdery mildew control. The frequency of QLR in vines not treated with quinoxyfen slowly declined from 65% in 2014 to 46% in 2016. Further research is needed to explain how, despite this QLR frequency, quinoxyfen applied to grapes in the field was still able to effectively control powdery mildew.

scholarly journals First Report of Leaf Blight of Dianthus chinensis Caused by Rhizoctonia solani

Plant Disease ◽  
2000 ◽  
Vol 84 (12) ◽  
pp. 1344-1344
Author(s):  
G. E. Holcomb ◽  
D. E. Carling
Keyword(s):  
United States ◽  
Rhizoctonia Solani ◽  
Gulf Coast ◽  
The United States ◽  
Anastomosis Group ◽  
Early Spring ◽  
Leaf Blight ◽  
Infected Leaf ◽  
First Report ◽  
Bedding Plant

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

scholarly journals Effect of Fungicide and Timing of Application on Soybean Rust Severity and Yield

Plant Disease ◽  
2009 ◽  
Vol 93 (3) ◽  
pp. 243-248 ◽  
Author(s):  
T. A. Mueller ◽  
M. R. Miles ◽  
W. Morel ◽  
J. J. Marois ◽  
D. L. Wright ◽  
...  
Keyword(s):  
United States ◽  
The United States ◽  
Field Trials ◽  
Soybean Rust ◽  
Growth Stages ◽  
Yield Losses ◽  
Treatment Timing ◽  
Progress Curve ◽  
Significant Yield ◽  
Rust Severity

Soybean rust, caused by Phakopsora pachyrhizi, is a devastating foliar disease of soybean that may cause significant yield losses if not managed by well-timed fungicide applications. To determine the effect of fungicide timing on soybean rust severity and soybean yield, field trials were completed in Paraguay (four locations), the United States (two locations), and Zimbabwe (one location) from 2005 to 2006. Treatments at each location included applications of tebuconazole, pyraclostrobin, or a combination of azoxystrobin + propiconazole, and in some locations pyraclostrobin + tebuconazole at the following soybean growth stages (GS): (i) GS R1 (beginning flowering), (ii) GS R3 (beginning pod), (iii) GS R5 (beginning seed), (iv) GS R1 + R3, (v) GS R3 + R5, and (vi) GS R1 + R3 + R5. Soybean yields from plots treated with fungicides were 16 to 114% greater than yields from no fungicide control plots in four locations in Paraguay, 12 to 55% greater in two locations in the United States, and 31% greater in Zimbabwe. In all locations, rust severity measured over time as area under the disease progress curve (AUDPC) was negatively correlated (r = –0.3, P < 0.0001) to yield. The effectiveness of any given treatment (timing of application and product applied) was often dependent on when rust was first detected and the intensity of its development. For example, when soybean rust was first observed before GS R3 (two locations in Paraguay), the plants in plots treated with a fungicide at GS R1 had the lowest AUPDC values and highest yields. When soybean rust was first observed after GS R3, plants treated with a fungicide at GS R3 and/or GS R5 had the lowest AUDPC values and highest yields with a few exceptions.

Fungicide sensitivity of Colletotrichum species causing bitter rot of apple in the Mid-Atlantic United States

Plant Disease ◽  
2021 ◽  
Author(s):  
Phillip L. Martin ◽  
Teresa Krawczyk ◽  
Kristen Pierce ◽  
Catherine Anne Thomas ◽  
Fatemeh Khodadadi ◽  
...  
Keyword(s):  
United States ◽  
Fungicide Resistance ◽  
Single Mode ◽  
The United States ◽  
Field Trials ◽  
In Vitro Tests ◽  
Atlantic Region ◽  
Low Frequencies ◽  
Bitter Rot

Apple growers in the Mid-Atlantic region of the United States have reported increased losses to bitter rot of apple. We tested the hypothesis that this increase is because the Colletotrichum population has developed resistance to commonly used single-mode-of-action (single-MoA) fungicides. We screened 220 Colletotrichum isolates obtained from 38 apple orchards in the Mid-Atlantic region for resistance to 11 fungicides in FRAC (Fungicide Resistance Action Committee) groups 1, 7, 9, 11, 12, and 29. Eleven (5%) of these isolates were resistant to FRAC group 1 with confirmed beta-tubulin E198A mutations, and two (< 1%) were also resistant to FRAC group 11 with confirmed cytochrome-b G143A mutations. Such low frequencies of resistant isolates indicate that fungicide resistance is unlikely to be the cause of any regional increase in bitter rot. A subsample of isolates was subsequently tested in vitro for sensitivity to every single-MoA fungicide registered for apple in the Mid-Atlantic US (22 fungicides; FRAC groups 1, 3, 7, 9, 11, 12, and 29), and thirteen fungicides were tested in field trials. These fungicides varied widely in efficacy both within and between FRAC groups. Comparisons of results from our in vitro tests with results from our field trials and other field trials conducted across the Eastern US suggested that EC₂₅ values (concentrations that reduce growth by 25%) are better predictors of fungicide efficacy in normal field conditions than EC₅₀ values. We present these results as a guideline for choosing single-MoA fungicides for bitter rot control in the Mid-Atlantic US.

Effect of Mowing Height and Fertility on Bermudagrass (Cynodon dactylon) Encroachment and Brown Patch Severity in Tall Fescue

2014 ◽  
Vol 28 (1) ◽  
pp. 225-232 ◽  
Author(s):  
Matthew Cutulle ◽  
Jeffrey Derr ◽  
David McCall ◽  
Adam Nichols ◽  
Brandon Horvath
Keyword(s):  
United States ◽  
Rhizoctonia Solani ◽  
Transition Zone ◽  
Tall Fescue ◽  
Nitrogen Fertilization ◽  
Cynodon Dactylon ◽  
The United States ◽  
Field Trials ◽  
Brown Patch ◽  
Fertilization Level

Tall fescue is a commonly used turfgrass in the temperate and transition zone areas of the United States. During hot, humid summers, tall fescue is under stress and is susceptible toRhizoctonia solani(brown patch) infection, causing turf thinning, leading to encroachment from weeds, such as bermudagrass. Field trials were established to evaluate the effect of mowing height and fertility programs on disease severity and bermudagrass encroachment in tall fescue. Mowing at 10 cm resulted in less bermudagrass encroachment than did a 6-cm mowing height. Increasing the nitrogen fertilization level from 49 to 171 and 220 kg N ha−1generally led to more bermudagrass encroachment at the 6-cm, but not the 10-cm, mowing height. Plots receiving 220 kg N ha−1annually at the 6-cm mowing height had the most brown patch. Turfgrass cover was greatest in plots mowed at 10 cm and receiving 220 kg N ha−1annually.

Characteristics of Physician Relocation Following Hurricane Katrina

2009 ◽  
Vol 95 (1) ◽  
pp. 6-12
Author(s):  
Kusuma Madamala ◽  
Claudia R. Campbell ◽  
Edbert B. Hsu ◽  
Yu-Hsiang Hsieh ◽  
James James
Keyword(s):  
Hurricane Katrina ◽  
Gulf Coast ◽  
General Medicine ◽  
The United States ◽  
Lessons Learned ◽  
Bivariate Analysis ◽  
Fisher Exact Test ◽  
Exact Test ◽  
Factors Associated ◽  
The Impact

ABSTRACT Introduction: On Aug. 29, 2005, Hurricane Katrina made landfall along the Gulf Coast of the United States, resulting in the evacuation of more than 1.5 million people, including nearly 6000 physicians. This article examines the relocation patterns of physicians following the storm, determines the impact that the disaster had on their lives and practices, and identifies lessons learned. Methods: An Internet-based survey was conducted among licensed physicians reporting addresses within Federal Emergency Management Agency-designated disaster zones in Louisiana and Mississippi. Descriptive data analysis was used to describe respondent characteristics. Multivariate logistic regression was performed to identify the factors associated with physician nonreturn to original practice. For those remaining relocated out of state, bivariate analysis with x2 or Fisher exact test was used to determine factors associated with plans to return to original practice. Results: A total of 312 eligible responses were collected. Among disaster zone respondents, 85.6 percent lived in Louisiana and 14.4 percent resided in Mississippi before the hurricane struck. By spring 2006, 75.6 percent (n = 236) of the respondents had returned to their original homes, whereas 24.4 percent (n = 76) remained displaced. Factors associated with nonreturn to original employment included family or general medicine practice (OR 0.42, 95 percent CI 0.17–1.04; P = .059) and severe or complete damage to the workplace (OR 0.24, 95 percent CI 0.13–0.42; P &lt; .001). Conclusions: A sizeable proportion of physicians remain displaced after Hurricane Katrina, along with a lasting decrease in the number of physicians serving in the areas affected by the disaster. Programs designed to address identified physician needs in the aftermath of the storm may give confidence to displaced physicians to return.

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