scholarly journals Influence of Grape Berry Age on Susceptibility to Guignardia bidwellii and Its Incubation Period Length

2002 ◽  
Vol 92 (10) ◽  
pp. 1068-1076 ◽  
Author(s):  
Lisa Emele Hoffman ◽  
Wayne F. Wilcox ◽  
David M. Gadoury ◽  
Robert C. Seem
Keyword(s):  
Incubation Period ◽  
Epidemiological Studies ◽  
Grape Berry ◽  
Period Length ◽  
Black Rot ◽  
Variable Effect ◽  
Guignardia Bidwellii ◽  
Age Related ◽  
Vitis Labruscana ◽  
Grape Black Rot

The period of fruit susceptibility to Guignardia bidwellii (anamorph Phyllosticta ampelicida), the causal agent of grape black rot, was determined in the field. Intact fruit were inoculated weekly from bloom until 8 weeks later with a suspension containing 2 × 105 conidia per ml. Disease progress was monitored approximately every 2 days until 3 to 5 weeks after inoculation, depending on the year and variety. Fruit of Vitis × labruscana ‘Concord’ exhibited a period of maximum susceptibility from midbloom until 2 to 4 weeks later, although some berries became symptomatic when inoculated 4 to 5 weeks postbloom. Fruit of V. vinifera ‘Chardonnay’ and ‘Riesling’ exhibited a period of maximum susceptibility from midbloom until 3 to 5 weeks later, although some berries retained their susceptibility until 6 to 7 weeks postbloom. These susceptible periods were approximately 2 to 4 weeks shorter than previously assumed. Fruit age at the time of inoculation affected the length of the incubation period (time from inoculation until symptom appearance). When the incubation period was defined in terms of degree hours (base = 0°C) accumulated after inoculation, DH50 values (the number of degree hours required to reach 50% of final disease severity) increased by at least 50% as berries neared the end of their susceptible period. Newly symptomatic berries continued to appear for over 1 month after inoculation of older fruit. Thus, age-related or ontogenic, host resistance was manifested as both a decline in susceptibility and a significant increase in incubation period length. The control of black rot is likely to be improved by tailoring the intensity of fungicidal protection to the abbreviated period of fruit susceptibility defined in this study. Furthermore, the efficacy of management programs and the results of epidemiological studies are likely to be misinterpreted unless the variable effect of fruit age on incubation period length is recognized.

scholarly journals A Cumulative Degree-Day-Based Model to Calculate the Duration of the Incubation Period of Guignardia bidwellii

Plant Disease ◽  
2012 ◽  
Vol 96 (7) ◽  
pp. 1054-1059 ◽  
Author(s):  
Daniel Molitor ◽  
Cathleen Fruehauf ◽  
Ottmar Baus ◽  
Beate Berkelmann-Loehnertz
Keyword(s):  
Incubation Period ◽  
Present Model ◽  
Developmental Stages ◽  
Black Rot ◽  
Phenological Stage ◽  
Degree Days ◽  
Fungal Development ◽  
Guignardia Bidwellii ◽  
Degree Day ◽  
Grape Black Rot

The duration of the incubation period of Guignardia bidwellii on leaves and clusters of Vitis vinifera strongly correlates to temperature. To describe this relationship mathematically, a new, cumulative degreeday- based model was developed. According to this model, first symptoms on leaves appear after reaching a threshold of 175 cumulative degree-days (calculated as the sum of average daily temperatures between 6 and 24°C starting on the day after the infection). On clusters, the duration of the incubation period is additionally affected by their respective developmental stages. For ‘Riesling’, the duration of the incubation period on clusters corresponds to the duration on leaves until reaching the phenological stage “berries beginning to touch“ but extends continuously with ongoing phenological development. Therefore, a correction factor recognizing cluster phenology was derived to calculate the cumulative degree-day thresholds for the occurrence of first symptoms on clusters after reaching “majority of berries touching”. Hence, this present model allows the estimation of fungal development and forecasts the appearance of new symptoms on leaves as well as on clusters, enabling growers to more precisely schedule curative as well as protective fungicide applications against grape black rot.

scholarly journals Factors Influencing the Efficacy of Myclobutanil and Azoxystrobin for Control of Grape Black Rot

Plant Disease ◽  
2003 ◽  
Vol 87 (3) ◽  
pp. 273-281 ◽  
Author(s):  
Lisa Emele Hoffman ◽  
Wayne F. Wilcox
Keyword(s):  
Black Rot ◽  
Alternative Respiration ◽  
Complete Control ◽  
Guignardia Bidwellii ◽  
Factors Influencing ◽  
Grape Black Rot ◽  
History Of ◽  
Commercial Vineyard ◽  
Strobilurin Fungicide

We studied several factors influencing the efficacy of the demethylation inhibitor (DMI) fungicide myclobutanil and the strobilurin fungicide azoxystrobin for control of grape black rot, caused by the pathogen Guignardia bidwellii (anamorph Phyllosticta ampelicida). The distribution of sensitivities to myclobutanil among G. bidwellii isolates from an “organic” vineyard (no previous exposure to synthetic fungicides, n = 50) and from a commercial vineyard with a history of DMI applications (n = 60) was determined in vitro. There was little difference between the two populations, and the range of sensitivities was narrow; for the composite population of 110 isolates, the value of the mean effective dose for 50% inhibition (ED50) was 0.04 mg/liter, and the most- and least-sensitive isolates were separated by a factor of 16. When applied from 2 to 6 days after inoculating grape seedlings with a suspension containing either 2 × 104 or 1 × 106 conidia per ml, myclobutanil (60 mg/liter) provided complete control of lesion development. When applied beyond 6 days after inoculation but prior to lesion appearance (9 to 11 days after inoculation, depending on temperature), it provided complete control of pycnidium production in those lesions that developed subsequently. In contrast, when applied 2 to 10 days after inoculation with 2 × 104 conidia per ml, azoxystrobin (128 mg/liter) provided only 78 to 63% control of lesion formation and erratic control of pycnidium formation, although conidium production was reduced by 85 to 68% across this range of treatments. Relatively little control was provided by azoxystrobin treatments following inoculation with 1 × 106 conidia per ml. On leaf disks treated with azoxystrobin at 20 mg/liter prior to inoculation, 8 to 43% of conidia from five G. bidwellii isolates germinated, and 4 to 19% formed appressoria. However, these processes were completely to near-completely inhibited when salicylhydroxamic acid (SHAM), which inhibits an alternative respiration pathway utilized to circumvent the activity of strobilurin fungicides, was added to the inoculum at 100 mg/liter. Thus, alternative respiration apparently allowed the conidia to germinate and form appressoria on azoxystrobin-treated leaves. When grape seedlings were sprayed with commercially formulated azoxystrobin at 200 mg/liter and inoculated the next day with G. bidwellii conidia, little or no disease was evident 4 weeks later. However, G. bidwellii pycnidia formed on up to 50% of the leaves from such plants when they were killed with paraquat 1 to 7 days after inoculation. These results suggest that latent infections became established on azoxystrobin-treated leaves and became active after the plants were killed with paraquat.

scholarly journals Production of Pycnidia and Conidia by Guignardia bidwellii, the Causal Agent of Grape Black Rot, as Affected by Temperature and Humidity

2017 ◽  
Vol 107 (2) ◽  
pp. 173-183 ◽  
Author(s):  
G. Onesti ◽  
E. González-Domínguez ◽  
V. Rossi
Keyword(s):  
Field Experiments ◽  
Growth Parameters ◽  
Effect Of Temperature ◽  
Black Rot ◽  
High Humidity ◽  
Guignardia Bidwellii ◽  
Leaf Lesion ◽  
Grape Black Rot ◽  
Effects Of Temperature ◽  
Grape Leaf

Black rot, caused by the fungus Guignardia bidwellii, is a polycyclic disease affecting grape leaves and berries. In environmentally controlled experiments and in a 3-year field study, the effects of temperature and relative humidity (RH) were assessed on the following growth parameters of G. bidwellii: (i) formation of pycnidia and cirri in grape leaf lesions, (ii) production and germination of conidia, and (iii) length of the period between lesion appearance and pycnidia production. Pycnidia were produced between 5 and 35°C and at 90 to 100% RH but more pycnidia were produced between 20 and 30°C. No pycnidia were produced at RH < 90%. The first pycnidia were produced in approximately 2 days after lesion appearance at ≥20°C and in 8 days at 5°C; pycnidia continued to be produced on the same lesion for 5 to 16 days after lesion appearance, depending on the temperature. Models were developed to describe the effect of temperature and RH on pycnidia production, accounting for 95 and 97% of variability, respectively. Cirri were extruded only between 15 and 35°C and mainly at 100% RH. Field experiments confirmed that pycnidia are produced for several days on a leaf lesion and that the length of the period between lesion appearance and pycnidia production depends on temperature. Overall, the findings showed that production of conidia requires high humidity; under field conditions, some hours at high humidity, which usually occur at nighttime, rather than constant high humidity may be sufficient.

scholarly journals Integrated Control of Grape Black Rot: Influence of Host Phenology, Inoculum Availability, Sanitation, and Spray Timing

2004 ◽  
Vol 94 (6) ◽  
pp. 641-650 ◽  
Author(s):  
Lisa Emele Hoffman ◽  
Wayne F. Wilcox ◽  
David M. Gadoury ◽  
Robert C. Seem ◽  
Duane G. Riegel
Keyword(s):  
Integrated Control ◽  
Black Rot ◽  
Complete Control ◽  
Guignardia Bidwellii ◽  
Grape Black Rot ◽  
Host Phenology ◽  
Spray Timing ◽  
Spray Regimes ◽  
Disease Pressure ◽  
And Control

The epidemiology and control of black rot (Guignardia bidwellii) was studied from 1995 to 1999 in vineyards in Dresden and Naples, NY, where disease pressure was moderate and extreme, respectively. The efficacy of serial applications of myclobutanil, provided at 2-week intervals and varied with respect to their number and time of initiation, was examined within the context of host phenology, inoculum availability, and sanitation. At Dresden, sprays applied over 4 weeks through the immediate prebloom stage provided only 13 to 91% control of diseased clusters, despite the release of 95% of the season's ascosporic inoculum during the period of fungicidal protection. However, applications immediately prior to bloom plus 2 and 4 weeks later, which afforded protection while fruit are highly susceptible to infection, provided virtually complete control. At Naples, where mummified berries were retained in the canopy after mechanical pruning, this same regime provided only approximately 80% disease control, but applying a fourth spray 2 weeks prebloom generally improved control. Hand-pruning mummies to the ground in selected plots significantly (P ≤ 0.05) improved control in some spray regimes. Although this sanitation practice did not affect inoculum dynamics through bloom, very few spores were recovered thereafter from mummies collected from the ground, whereas abundant ascospores and conidia were recovered from mummies in the trellis for an additional 6 to 8 weeks.

Grading of age-related maculopathy for epidemiological studies

Ophthalmology ◽  
2003 ◽  
Vol 110 (8) ◽  
pp. 1540-1544 ◽  
Author(s):  
Redmer van Leeuwen ◽  
Usha Chakravarthy ◽  
Johannes R Vingerling ◽  
Corina Brussee ◽  
Ada J Hooghart ◽  
...  
Keyword(s):  
Epidemiological Studies ◽  
Age Related

The Epidemilogy of Chronic Venous Ulcer: Some Unanswered Questions

2000 ◽  
Vol 15 (3-4) ◽  
pp. 106-109
Author(s):  
C. V. Ruckley
Keyword(s):  
Chronic Venous Insufficiency ◽  
Venous Insufficiency ◽  
Varicose Veins ◽  
Clinical Manifestations ◽  
Epidemiological Studies ◽  
Therapeutic Interventions ◽  
Venous Disease ◽  
Clinical Classification ◽  
Age Related

Objective: To highlight gaps in knowledge concerning the epidemiology of chronic venous insufficiency and to indicate what future studies are required. Methods: Existing classifications are compared. Limitations of epidemiological studies are defined. Data from published series and from the Edinburgh Vein Study are presented. Synthesis: The Basle 1978 classification of chronic venous insufficiency (CVI) is a purely clinical classification in which the earliest grade is corona phlebectatica. The Porter 1988 classification of CVI attempted to correlate clinical grades with sites of venous incompe-tence. However, a consistent relationship does not exist. The CEAP classification separates the clinical grades (which do not include corona phlebectasia) from the anatomical segments. The CEAP clinical classification covers a range of venous manifestations but is not consistent. There is a need for further consideration of classifications. Published selected series of patients show that the frequency of incompetence in both deep and superficial systems increases in proportion to the severity of the clinical manifestations of venous disease. To understand the significance of these data we need to know the patterns of venous incompetence in the general population. Data from 1566 subjects between the ages of 18 and 64 years in the Edinburgh Vein Study, a randomly selected cross-section of members of the Edinburgh population, showed that the prevalence of CVI was age-related and was present in 9.2% of men and 6.6% of women. Men had a significantly higher frequency of reflux in the deep system than women. In order to direct therapeutic interventions where they are most appropriate we need to know which patients with the early stages of varicose veins progress to CVI and which patients with early CVI progress to the serious skin complications. Conclusions: Key information concerning the natural history of venous disease and its evolution in relation to haemodynamic abnormalities awaits the findings of longitudinal-cohort epidemiological studies which include the duplex scanning of large populations.

scholarly journals Dietary Antioxidants, Macular Pigment, and Glaucomatous Neurodegeneration: A Review of the Evidence

Nutrients ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 1002 ◽  
Author(s):  
Thomas Lawler ◽  
Yao Liu ◽  
Krista Christensen ◽  
Thasarat S. Vajaranant ◽  
Julie Mares
Keyword(s):  
Primary Open Angle Glaucoma ◽  
Open Angle Glaucoma ◽  
Visual Field Loss ◽  
Evidence Base ◽  
Epidemiological Studies ◽  
Macular Pigment ◽  
Eye Disease ◽  
Open Angle ◽  
Dietary Antioxidants ◽  
Age Related

Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness worldwide, and the prevalence is projected to increase to 112 million worldwide by 2040. Intraocular pressure is currently the only proven modifiable risk factor to treat POAG, but recent evidence suggests a link between antioxidant levels and risk for prevalent glaucoma. Studies have found that antioxidant levels are lower in the serum and aqueous humor of glaucoma patients. In this review, we provide a brief overview of the evidence linking oxidative stress to glaucomatous pathology, followed by an in-depth discussion of epidemiological studies and clinical trials of antioxidant consumption and glaucomatous visual field loss. Lastly, we highlight a possible role for antioxidant carotenoids lutein and zeaxanthin, which accumulate in the retina to form macular pigment, as evidence has emerged supporting an association between macular pigment levels and age-related eye disease, including glaucoma. We conclude that the evidence base is inconsistent in showing causal links between dietary antioxidants and glaucoma risk, and that prospective studies are needed to further investigate the possible relationship between macular pigment levels and glaucoma risk specifically.

scholarly journals Incubation period for outbreak-associated, non-typhoidal salmonellosis cases, Minnesota, 2000–2015

2018 ◽  
Vol 146 (4) ◽  
pp. 423-429 ◽  
Author(s):  
D. Eikmeier ◽  
C. Medus ◽  
K. Smith
Keyword(s):  
Incubation Period ◽  
Period Length ◽  
Accurate Description ◽  
Vehicle Type ◽  
Day Range ◽  
Incubation Periods

AbstractIncubation period for non-typhoidal Salmonella (NTS) infections is generally reported as 6–72 h despite numerous reports of foodborne NTS outbreaks with median incubation periods >3 days. We summarised 16 years of Minnesota foodborne NTS outbreaks to better estimate the expected range of incubation periods for NTS infections. Of the 1517 NTS outbreak cases, 725 had enough data to calculate a precise incubation period. The median incubation period was 45 h; 77 (11%) cases had incubations ⩽12 h and 211 (29%) cases had incubations >72 h. Incubation period length varied by outbreak vehicle type, Salmonella serotype and outbreak setting. Based on our data, a more accurate description would be that the incubation of NTS infection is usually from 12 to 96 h, that incubations in >96 to 144 h (>4 to 6-day) range are not unusual and that incubations from 7 to 9 days and occasionally longer also occur.

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