Diagrammatic scale to assess downy mildew severity in melon

The downy mildew, caused by Pseudoperonospora cubensis, is an important melon disease in Northeast Brazil. Considering the lack of standard methods for its assessment, a diagrammatic scale was developed with 2, 4, 8, 16, 32, 64, 82, and 96% of affected leaf area. The scale was then checked for its accuracy, precision, and reproducibility in estimating downy mildew severity. The diagrammatic scale was validated by eight disease raters; using 50 leaves with different severity levels, previously measured using the software Assess®. Two evaluations were performed on the same set of leaves, but in a different sequence order, by the same raters, within a 15-day interval. The accuracy and precision of each rater was determined by simple linear regression between the actual and the estimated severity. The scale provided good levels of accuracy (means of 87.5%) and excellent levels of precision (means of 94%), with absolute errors concentrated around 10%. Raters showed great repeatability (means of 94%) and reproducibility (>90% in 90.3% of cases) of estimates. Therefore, we could conclude that the diagrammatic scale presented here was suitable for evaluating downy mildew severity in melon.

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Elaboration and validation of diagrammatic scale for lettuce powdery mildew

Summa Phytopathologica ◽

10.1590/0100-5405/175851 ◽

2018 ◽

Vol 44 (2) ◽

pp. 116-121 ◽

Cited By ~ 1

Author(s):

Guilherme de Resende Camara ◽

Laedio Magno Busato ◽

Bárbara Favalessa Almeida ◽

Willian Bucker Moraes

Keyword(s):

Powdery Mildew ◽

Linear Regression ◽

Leaf Area ◽

Epidemiological Study ◽

Logarithmic Scale ◽

Accuracy And Precision ◽

Severity Levels ◽

Hydroponic Systems ◽

Lettuce Powdery Mildew ◽

Diagrammatic Scale

ABSTRACT Powdery mildew, caused by Oidium sp., is a disease of great importance in hydroponic crops of lettuce. However, in Brazil, there is scarce research focused on the epidemiological study of this disease, as standardized methods are necessary to quantify the disease severity in hydroponic systems. Thus, a logarithmic scale was developed at levels of 0.37, 1, 2, 4, 8, 16, 32 and 74% injured leaf area, testing the parameters accuracy and precision. The proposed scale was validated by eight evaluators, of whom four were experienced and four were inexperienced, and they used 50 leaves showing symptoms of the disease at different severity levels, previously measured with the aid of QUANT® software. Two evaluations were performed with a 48-h interval, in which the evaluators visually estimated distinct sequences of leaves. Linear regression was used to determine the accuracy and the precision of each evaluator. The proposed scale showed satisfactory results of accuracy and precision, and despite the inexperience of four evaluators, absolute errors were in the range of 8% after training. The proposed scale was adequate to estimate the severity of powdery mildew on lettuce.

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Interactive Effects of Temperature and Leaf Wetness Duration on Sporangia Germination and Infection of Cucurbit Hosts by Pseudoperonospora cubensis

Plant Disease ◽

10.1094/pdis-07-11-0560 ◽

2012 ◽

Vol 96 (3) ◽

pp. 345-353 ◽

Cited By ~ 22

Author(s):

K. N. Neufeld ◽

P. S. Ojiambo

Keyword(s):

Leaf Area ◽

Downy Mildew ◽

Disease Severity ◽

Leaf Wetness ◽

Pseudoperonospora Cubensis ◽

Weibull Function ◽

Leaf Wetness Duration ◽

Cucurbit Downy Mildew ◽

Host Type ◽

Effects Of Temperature

Outbreaks of cucurbit downy mildew caused by Pseudoperonospora cubensis are dependent on the weather but effects of temperature and leaf wetness duration on infection have not been studied for different cucurbits. To determine the effects of these two weather variables on sporangia germination and infection of cucurbit host types by P. cubensis, three host types; cucumber (‘Straight 8’), cantaloupe (‘Kermit’), and acorn squash (‘Table Queen’), were inoculated and exposed to leaf wetness durations of 2 to 24 h at six constant temperatures ranging from 5 to 30°C in growth-chamber experiments. Sporangia germination was assessed after each wetness period, and leaf area infected was assessed 5 and 7 days after inoculation. Germination of sporangia was highest on cantaloupe (16.5 to 85.7%) and lowest on squash (10.7 to 68.9%), while disease severity was highest and lowest on cucumber and cantaloupe, respectively. Host type, temperature, wetness duration and their interactions significantly (P < 0.0001) affected germination and disease severity. Germination and disease data for each host type were separately fitted to a modified form of a Weibull function that characterizes a unimodal response and monotonic increase of germination or infection with temperature and wetness duration, respectively. The effect of host type on germination and infection was characterized primarily by differences in the upper limit parameter in response to temperature. Differences among host types based on other parameters were either small or inconsistent. Temperature and wetness duration that supported a given level of germination or infection varied among host types. At 20°C, 15% leaf area infected was expected following 2, 4, and 8 h of wetness for cucumber, squash, and cantaloupe, respectively. When temperature was increased to 25°C, 15% disease severity was expected following 3, 7, and 15 h of wetness for cucumber, squash, and cantaloupe, respectively. Risk charts were constructed to estimate the potential risk of infection of cucurbit host types by P. cubensis based on prevailing or forecasted temperature and leaf wetness duration. These results will improve the timing and application of the initial fungicide spray for the control of cucurbit downy mildew.

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Diagrammatic scale for measuring severity of gray mould in thornless Castilla blackberry (Rubus glaucus Benth)

Ciência Rural ◽

10.1590/0103-8478cr20190859 ◽

2020 ◽

Vol 50 (11) ◽

Author(s):

Sarah Muñoz Arias ◽

Gloria Edith Guerrero Álvarez ◽

Paula Andrea González Patiño

Keyword(s):

Linear Regression ◽

Botrytis Cinerea ◽

National Level ◽

Economic Losses ◽

Simple Linear Regression ◽

Photographic Images ◽

Gray Mould ◽

Precision And Accuracy ◽

Imagej Software ◽

Diagrammatic Scale

ABSTRACT: Gray mould, caused by the fungus Botrytis cinerea Pers., is a disease that largely affects the crops of Rubus glaucus Benth. (Castilla blackberry) in Colombia. In spite of the economic losses that it causes in the production of Castilla blackberry at national level, a standardized method to quantify the disease severity caused by this fungus in the fruits has not yet been reported. In the present work, a diagrammatic scale was prepared to assess gray mould severity in thornless fruits of R. glaucus. The proposed scale showed the levels of 5, 10, 20, 40, 60, 80, and 100%. Photographic images were obtained for each of these levels, which were processed using the ImageJ software. The scale was validated by 13 evaluators who assessed affected fruits with and without the scale. The precision and accuracy of each evaluator was determined by simple linear regression between actual and estimated severity. The evaluators showed better precision, accuracy, and reproducibility in the assessments performed with the scale. The proposed scale is appropriate to estimate the severity of gray mould in R. glaucus fruits.

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Relationships Between Airborne Pseudoperonospora cubensis Sporangia, Environmental Conditions, and Cucumber Downy Mildew Severity

Plant Disease ◽

10.1094/pdis-05-13-0567-re ◽

2014 ◽

Vol 98 (5) ◽

pp. 674-681 ◽

Cited By ~ 20

Author(s):

L. L. Granke ◽

J. J. Morrice ◽

M. K. Hausbeck

Keyword(s):

Leaf Area ◽

Downy Mildew ◽

Disease Severity ◽

Leaf Wetness ◽

Pseudoperonospora Cubensis ◽

Disease Occurrence ◽

Benton Harbor ◽

Cucumber Downy Mildew ◽

High Disease Severity ◽

Symptomatic Leaf

Airborne Pseudoperonospora cubensis sporangia were collected 0.5 m above the ground from May to late September or early October 2010 and 2011 in unsprayed cucumber (Cucumis sativus) fields in Benton Harbor and Frankenmuth, MI. Cucumber downy mildew incidence and severity were evaluated weekly within each field from June until September or October. The first airborne sporangium was detected before the crop was planted for each site-year. The greatest numbers of airborne sporangia were detected when moderate to high disease severity (≥5% symptomatic leaf area) was detected within the field. Fewer airborne sporangia were present with low disease severity (<5% symptomatic leaf area), and even fewer were detected prior to planting the cucumber crop. The number of airborne sporangia detected, time post planting, planting number (first versus second versus third planting), temperature, and leaf wetness were positively associated and solar radiation was negatively associated with disease occurrence for at least one site-year. Michigan growers currently use an aggressive, calendar-based fungicide program to manage cucumber downy mildew. Because airborne sporangium concentrations were one of the most important factors identified in this study, the current fungicide recommendation of decreasing the spray interval following disease detection in an area is warranted.

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Development and validation of diagrammatic scales to evaluate damage by the two-spotted spider mite (Tetranychus urticae) in peanut

Revista de la Facultad de Ciencias Agrarias UNCuyo ◽

10.48162/rev.39.024 ◽

2021 ◽

Vol 53 (1) ◽

pp. 254-261

Author(s):

Ana Cecilia Crenna ◽

Claudio Marcelo Oddino ◽

Santiago Ferrari ◽

Jorge Antonio Giuggia ◽

Diego Giovanini ◽

...

Keyword(s):

Linear Regression ◽

Leaf Area ◽

Tetranychus Urticae ◽

Spider Mite ◽

Mean Values ◽

Fundamental Parameters ◽

Peanut Crop ◽

Two Spotted Spider Mite ◽

Development And Validation ◽

Diagrammatic Scale

Argentina is the second largest peanut (Arachis hypogaea L.) exporter in the world. The main peanut pest in our country is the two-spotted spider mite (Tetranychus urticae Koch 1836). To date, there is no validated method to quantify this pest. The aim of this work was to develop and validate a logarithmic diagrammatic scale to assess damage by the two-spotted spider mite in peanut. In 2015-16, 200 leaflets were collected from a plot infested with the pest. Damaged leaf area (DLA) was calculated using SisCob software. Six-, seven-, eight- and nine-class scales were proposed. Mean values for each class and scale were obtained with 2-LOG. Leaflets were analyzed by 13 raters who used the four proposed scales. Precision and accuracy were determined by simple linear regression between the DLA and estimated damaged leaf area. Reproducibility was determined by linear regression between estimates of raters combined in pairs. The seven-class scale was the best validated one for all the parameters. Most raters showed constant deviations and overestimated DLA, whereas only one rater presented systematic deviations. This seven-class scale is the first developed and validated one to evaluate two-spotted spider mite damage to peanut in Argentina. Highlights According to the validation results, the seven-class diagrammatic scale was the best one in terms of accuracy, precision and reproducibility with values above 0.80, 0.75 and 0.75 respectively. The scales are useful tools for pest assessment, fundamental parameters for integrated pest management. The seven-class scale is the first one developed and validated for evaluating damage by the two-spotted spider mite in peanut crop in Argentina. With this scale a loss function will be calculate which will allow the estimation of the EIL of this pest.

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Elaboração e validação de diagramas de área padrão (DAP) para avaliação da severidade do míldio (Peronospora variabilis Gäum) em quinoa (Chenopodium quinoa Willd)

Revista Agraria Academica ◽

10.32406/v4n4/2021/43-54/agrariacad ◽

2021 ◽

Vol 4 (4) ◽

pp. 43-54

Author(s):

Pablo Israel Álvarez-Romero ◽

◽

Virginia Mariño-Frías ◽

Carlos Francisco Carpio-Coba ◽

Ana Francisca Ferreira-Ferreira ◽

...

Keyword(s):

Downy Mildew ◽

Chenopodium Quinoa ◽

Epidemiological Studies ◽

Accuracy And Precision ◽

Severity Levels

The quinoa downy mildew is one of the major diseases affecting quinoa in Ecuador. Considering the lack of standardized methods to quantify this disease on leaves, the aim of this study was to develop a standard area diagram to quantify the severity of the quinoa downy mildew. To standardize the assessment, we developed two sets of standard area diagrams. To validate the diagram, twelve raters estimated the severity of 50 scanned leaf images at different severity levels. The proposed diagram with linear increments provided good levels of accuracy and precision, constituting thus a useful tool in epidemiological studies and for the development of strategies to control the quinoa downy mildew.

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Diagrammatic scale for assessment of soybean rust severity

Fitopatologia Brasileira ◽

10.1590/s0100-41582006000100011 ◽

2006 ◽

Vol 31 (1) ◽

pp. 63-68 ◽

Cited By ~ 110

Author(s):

Cláudia V. Godoy ◽

Lucimara J. Koga ◽

Marcelo G. Canteri

Keyword(s):

Glycine Max ◽

Scale Validation ◽

Soybean Rust ◽

Phakopsora Pachyrhizi ◽

Stimulus Response ◽

Accuracy And Precision ◽

Rust Severity ◽

Severity Levels ◽

Diagrammatic Scale

A diagrammatic scale to assess soybean (Glycine max) rust severity, caused by the fungus Phakopsora pachyrhizi, was developed in this study. Leaflets showing different severity levels were collected for determination of the minimum and maximum severity limits; intermediate levels were determined according to "Weber-Fechner's stimulus-response law". The proposed scale showed the levels of 0.6; 2; 7; 18; 42, and 78.5%. Scale validation was performed by eight raters (four inexperienced and four experienced), who estimated the severity of 44 soybean leaflets showing rust symptoms, with and without the use of the scale. Except for rater number eight, all showed a tendency to overestimate severity without the aid of the diagrammatic scale. With the scale, the raters obtained better accuracy and precision levels, although the tendency to overestimate was maintained. Experienced raters were more accurate and precise than inexperienced raters, and assessment improvements with the use of the scale were more significant for inexperienced raters.

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ImageJ software as an alternative method for estimating leaf area in oats

Acta Agronómica ◽

10.15446/acag.v69n3.69401 ◽

2021 ◽

Vol 69 (3) ◽

Author(s):

Thomas Newton Martin ◽

Glauber Monçon Fipke ◽

José Eduardo Minussi Winck ◽

José Abramo Marchese

Keyword(s):

Standard Deviation ◽

Linear Regression ◽

Leaf Area ◽

Coefficient Of Variation ◽

Estimation Methods ◽

Linear Regression Equation ◽

Simple Linear Regression ◽

Oat Cultivars ◽

Highly Correlated ◽

Imagej Software

The aim of this study was to compare two methods of estimating leaf area (leaf area meter LI-COR 3100 and ImageJ software) in oats. Renascem black oats and UTF Iguaçu white oats cultivars were evaluated. All the leaves of one plant per plot, with six repetitions, were evaluated every seven days to obtain five assessments for each cultivar. The leaves were identified and fixed on a white A4 sheet of paper with an indication of a known area (45 cm²), photographed and evaluated using a leaf area meter (LI-3100 - LI-COR). Leaf area was then estimated using ImageJ software. Estimates were obtained for standard deviation and coefficient of variation, and a simple linear regression equation was estimated based on the two estimation methods. Mean variances were tested using the ‘F’-test and the means compared by the ‘t’-test. There was no difference between the leaf areas found by both methods. In addition, they were highly correlated, and variances were homogeneous. We concluded that ImageJ software can be used instead of the leaf area meter on the two oat cultivars evaluated.

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Elaboration and validation of a diagrammatic scale to assess downy mildew severity in grapevine

Ciência Rural ◽

10.1590/0103-8478cr20131548 ◽

2014 ◽

Vol 44 (8) ◽

pp. 1384-1391 ◽

Cited By ~ 17

Author(s):

Cláudia Regina Scapin Buffara ◽

Francislene Angelotti ◽

Rafael Augusto Vieira ◽

Amauri Bogo ◽

Dauri José Tessmann ◽

...

Keyword(s):

Downy Mildew ◽

Disease Severity ◽

Economic Losses ◽

Grapevine Downy Mildew ◽

Stimulus Response ◽

Black And White ◽

Color Scale ◽

Accuracy And Precision ◽

Grapevine Leaves ◽

Diagrammatic Scale

The downy mildew, caused by Plasmopora viticola, is one of the most important grapevine (Vitis vinifera) diseases in Southern Brazil, causing defoliation and economic losses. The evaluation of disease severity is an important decision for adoption of strategies and tactics for disease control. Therefore, the objective of this work was to elaborate and to validate a diagrammatic scale to assess downy mildew severity in grapevine, respecting the limitations of visual acuity. The diagrammatic scale with seven levels of disease severity of 1, 3, 6, 12, 25, 50 and 75% was developed in two versions of black-and-white and color scale. The scales were tested and validated by eight raters with and without previous experience with grapevine downy mildew. The raters estimated the severity of 30 grapevine leaves with different downy mildew severity, with and without the use of the scales. Minimum, intermediate and maximum severity levels were collected according to Weber-Fechner's stimulus-response law. The accuracy and precision were analyzed by linear regression between the actual and the estimated severity. Actual severity was assessed with ASSESS(r) Program. The scales provided good levels of accuracy (means of 88%) and excellent levels of precision (means of 95%). The raters showed great precision and accuracy when used the diagrammatic scale. The color scale provided more precise and accurate estimates than the black-and-white scale. The scale proposed in this work presented appropriate applicability for downy mildew evaluation in grapevine.

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The Contribution of Sexual Identity Towards the Students’ Perception of Lesbian, Gay, Bisexual, and Transgender

Journal of Educational and Learning Studies ◽

10.32698/0642 ◽

2019 ◽

Vol 2 (2) ◽

pp. 120

Author(s):

Wiwi Delfita ◽

Neviyarni S. ◽

Riska Ahmad

Keyword(s):

Regression Analysis ◽

Linear Regression ◽

Sexual Identity ◽

Student Perceptions ◽

Undergraduate Students ◽

Linear Regression Analysis ◽

Sampling Technique ◽

Simple Linear Regression ◽

Simple Linear Regression Analysis ◽

Bisexual And Transgender

Some students perceive lesbian, gay, bisexual, and transgender (LGBT) positively, even though LGBT is a sexual deviation that is not appropriate with values and norms. There are several factors that influence an individual's perception of LGBT, including sexual identity. This study aims at looking at the contribution of sexual identity to student perceptions about LGBT. This research used a quantitative approach with a descriptive method and a simple linear regression analysis. The sample of this research was 385 taken from 15.752 undergraduate students of Universitas Negeri Padang which the sample was drawn by using the Slovin formula and continued with a Proportional Random Sampling technique. The instrument used was the Guttman model's sexual identity scale and the scale of students' perceptions of the LGBT Likert model. After analyzing the data with the descriptive technique and the simple linear regression analysis, the results showed that sexual identity significantly contributed to the students' perceptions of LGBT. This research has implications as a basis for counselors to help students avoid sexual identity mismatches and prevent the emergence of positive perceptions of LGBT.

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