Diagrammatic Scale Research Articles

Diagrammatic scale for quantifying severity of brown leaf spot on Carya illinoinensis.

Brown leaf spot disease, caused by the fungus Ragnhildiana diffusa, is responsible for losses in pecan orchards and quantification is essential in order to conduct epidemiological studies to establish levels of productivity losses, and assess control strategies. Therefore, the aim of this study was to develop and validate a diagrammatic scale for assessing the severity of brown leaf spot in pecan. 240 symptomatic leaflets were collected from adult trees in Anta Gorda, in the Brazilian state of Rio Grande do Sul, and used to assess the current percentage severity of the disease. The scale was based on the minimum and maximum observed severity of the disease, with six graduations defined according to the Weber-Fechner Visual Stimulus Law. The scale therefore consisted of eight levels (1.5, 4.6, 10.6, 17.3, 39.5, 65.1, 77.5, and 98%). The estimates of eight evaluators provided a basis for validating the scale. They made estimates of disease severity on 40 symptomatic digitalized pecan leaflets first, without using the scale and then referring to it. The scale provided greater precision, accuracy, and reproducibility of estimates and should result in more reliable epidemiological studies.

Reaction of Banana (Musa spp. L.) genotypes to yellow Sigatoka (Pseudocercospora musae (Zimm.) on Brazil’s central plateau and an epidemiological study of the disease Progress curves comparing four non-flexible models

Banana (Musa spp.) is cultivated throughout Brazil, with genotypes varying from region to region. Yellow Sigatoka disease (Pseudocercospora musae) is one of the most common foliar diseases of banana, causing severe losses when it is not properly managed. The objectives of this study were to evaluate banana genotypes for their reaction to yellow Sigatoka infection, and to perform an epidemiological study of this disease to have a better understanding of how it progresses under the environmental conditions of the Brazilian Cerrado. The reaction of 21 genotypes of banana to the infection by P. musae was evaluated in an experiment at Embrapa Cerrados (Planaltina, DF, Brazil), between August 2009 and January 2011, using a diagrammatic scale adapted from Stover, which ranged from 1 ( 51% leaf area showing symptoms). Assessments occurred every 15 days. At the end of the evaluation period the mean area under the disease progress curve (AUDPC) for each rated material was calculated. Genotypes were selected by Embrapa Mandioca e Fruticultura Tropical and separated into four sets: Cavendish/Gros Michel, Pome-Pacovan, Pome-Prata-ana and Silk/Mysore. An epidemiological study of the disease progress curve for each genotype was carried out to evaluate which non-flexible model (Monomolecular, Logistic, Exponential or Gompertz) would have the best fit to the disease severity progress curve data. Each set revealed genotypes with significant resistance to Yellow-Sigatoka. In the Pome-Pacovan set, resistance was observed in genotypes ‘Vitoria’, ‘PV 94–01’, ‘Pacovan Ken’, ‘Japira ‘and ‘PV 79–34′; in the Silk/Mysore genotypes ‘Caipira’, ‘YB 42–03′, ‘YB 42–07′ and ‘BRS Tropical’; in the Pome-Prata-ana set, genotypes ‘PA 94–01′, ‘BRS Platina’ and ‘BRS Garantida’; and in the Cavendish/Gros Michel set the genotype ‘Bucaneiro’. The monomolecular model displayed the best fit, with consistently low mean square error (MSE) values for all banana genotypes presented in this study.

Temporal progression of foliar plant diseases in corn hybrids

The environment’s impact on foliar disease growth in annual crops and the various types of differentiation must be investigated to adapt effective disease control strategies. We studied the temporal progression of foliar disease complexes in 14 commercial corn (Zea mays L.) hybrids during the 2015/2016 crop season (Ipameri, Goiás, Brazil). The experiment consisted of 10 blocks and evaluated foliar disease severity using a diagrammatic scale. The evaluations occurred at 47, 53, 59, 74, 81 and 95 days after planting. At each time point, a plant was chosen randomly from each block (10 plants total), and the diseases causing foliar damage were identified. The areas under the disease progression curves (AUDPCs) and yields were calculated. Dependent variables were evaluated using a principal component analysis to study relationships between the hybrids and the disease severity on each leaf (biplot). Heatmaps were used to determine which leaves demonstrated the greatest disease severity and temporal disease progression, and an adjusted linear correlation model was used to predict yield relative to AUDPC. The foliar disease complex consisted of helmintosporiosis, common rust, macrospora leaf spot, cercosporiosis and maize white spot. The Ns90PRO© hybrid showed limited disease progression and; therefore, was considered more resistant and consequently had a lower AUDPC value. The Dow2B610PW© hybrid showed greater disease progression. Agroceres7098PRO2© had a greater yield and consequently a lower AUDPC value, while Lg6050PRO2© had a lower yield and a higher AUDPC value. In general, the more advanced the phenological stage, the more severe the leaf disease; however, disease progression (from plant base to plant tip) was genotype- dependent.

Winter pruning: option for management against alternaria brown spot (Alteraria alternata f. sp. citri) in Honey Murcott tangor [Citrus reticulata Blanco x C. sinensis (L.) Osbeck

Alternaria brown spot (ABS), caused by Alternaria alternata f. sp. citri, is the main fungal disease plaguing tangerines. The main symptoms are falling leaf and fruit, resulting in the loss of production and quality. The initial symptoms in leaves are characterized by small brown or black spots, surrounded, or not, by yellowish halos. In the fruit, dark cortical patches appear that can easily break. In this study, the winter pruning of the plants was investigated to complementary control of ABS. The experiment was conducted in 10-year-old Honey Murcott tangor plants, where two treatments were applied: pruning in winter and no pruning, using a randomized block design with ten replicates. The treatment of winter pruning was performed before the flowering of the plants (September in Brazil), where the branches were cut close to the trunk, the thicker branches were removed. The chemical control was performed in both treatments. Evaluations of disease severity in fruit were performed using a diagrammatic scale; the disease incidence and area under the disease progress curve (AUDPC) were also calculated. The fruit drop and yield (t ha-1) of the plants were quantified, and the temperature and humidity inside the canopy of the plants were measured. Winter pruning had a positive effect on ABS management since it provided a decrease in incidence, severity, and AUDPC values. Fruit fall was reduced, resulting in greater productivity for Honey Murcott tangor plants. The results confirmed the positive effect of winter pruning on the management of alternaria brown spot.

Diagrammatic scale for severity evaluation of the Eremanthus erythropappus–Puccinia velata pathosystem

AbstractCandeia (Eremanthus erythropappus (DC.) MacLeish), a native forest species from South America, has garnered commercial interest due to its production of essential oil that contains alpha‐bisabolol. This compound is widely used in the pharmaceutical and cosmetics industry, with approximately 80% of Brazilian production being exported. Since candeia rust (Puccinia velata) has only been reported in Brazil, little is known about its epidemiology and control. There is no methodology to quantify rust severity in candeia, justifying the elaboration and validation of a diagrammatic scale containing eight levels of disease severity based on leaf area coverage (0.25%, 0.5%, 1%, 2%, 4%, 8%, 16% and 32%). In a natural sampling of disease in the field, 95% of the leaves showed severity below 16%, with the remaining 5% showing severities between 16% and 32% of leaf area. Validation of the proposed diagrammatic scale was performed by assessing the results from 10 inexperienced evaluators, performing evaluations of three leaves with different severity levels. The evaluations were performed at 7‐day intervals; in the first instance, severity values were assigned without the diagrammatic scale, and for the second attempt, the scale proposed in this study was used. The accuracy and precision of the severity estimates produced by each evaluator compared to the real severity was analysed by linear regression and by Lin's statistics. The reproducibility of the estimates was evaluated by analysing the coefficient of determination of linear regressions by pairs of evaluators. The scale provided adequate levels of accuracy, precision, repeatability and reproducibility, indicating the proposed scale was a suitable method for quantifying the severity of candeia rust.

Development and validation of a diagrammatic scale for quantifying maize leaf spots caused by Diplodia macrospora

The objective of this study was to develop and validate a diagrammatic scale to evaluate the severity of spots on maize leaves caused by the fungus Diplodia macrospora. Severity ranged between the minimal (0.5%) and maximal (55%) limits of disease severity, and intermediate severity levels were defined according to the "Weber-Fechner stimulus response law". The proposed scale describes six levels of severity based on how much of the leaf is affected: 0.5%, 3%, 8%, 23%, 36%, and 55%. Validation was carried out by eight evaluators, four inexperienced and four experienced. They estimated the severity of disease in 60 maize leaves, with and without the proposed diagrammatic scale. A relationship was shown by regression analysis between estimated and actual severity, with and without the use of the scale. When both inexperienced and experienced evaluators used the scale, they were able to estimate disease severity more accurately and precisely.

Assessing Spirituality on Two Dimensions: Closeness to God and Focal Orientation

ABSTRACTAssessing the nature of people’s relationships with God or the Divine is a central concern in the psychology of religion. We developed an intuitive, single-item diagrammatic scale which measures spirituality along two dimensions: (1) closeness to God or the Divine, and (2) the focus of that relationship as aimed at understanding either God (theo-focused) or the Self (ego-focused). In predominantly Christian and SBNR US samples, we found that the closeness dimension (from distant to close) was highly correlated with awareness of God’s presence and also with various measures of religiosity and belief in a personal God. Additionally, focal orientation discriminated between different aspects of religiosity/spirituality. Theo-focused spirituality was associated with religious beliefs and practices such as religious commitment, belief in a personal God, and religious service attendance. Moreover, it was a positive predictor of social responsibility, belief in a dangerous world, and support for government spending on the military. In contrast, ego-focused spirituality was associated with an eclectic combination of unorthodox religious beliefs, an individualistic approach to spirituality, as well as an interest in science, support for government spending on scientific research, and environmentalism. Finally, we found similar between-group differences in closeness and focal orientation across the US, UK, and India. We expect that this short, intuitive measure will be useful for better understanding a wide range of relationships with the Divine.

Diagrammatic scale for assessment of alternaria brown spot severity on tangerine leaves

Alternaria brown spot (ABS) is one of the main diseases of tangerine worldwide. It is necessary to use a practical and reliable method to quantify the disease severity of ABS and thus suggest management strategies. Thus, a diagrammatic scale (DS) constructed with color photographs was developed and validated to quantify the disease severity. Leaves were collected from crops and a nursery with different levels of ABS symptoms to determine the real severity digitally. The scale levels were determined according to the minimum and maximum severity values found and based on the frequency distribution of severity values. The DS validation was carried out by eleven assessors who estimated the severity of 50 leaves with different symptom levels. One assessment was performed without the DS and two using the DS at seven day intervals. The precision, accuracy, repeatability and reproducibility of the estimates were measured. The developed DS has nine score levels: 0 (0%), 1 (0.1–0.49%), 2 (0.5–1.0%), 3 (1.1–2.0%), 4 (2.1–4.0%), 5 (4.1–8%), 6 (8.1–18%), 7 (18.1–30%) and 8 (30.1–50%). The linear regression and Lin’s concordance correlation coefficient (LCCC) demonstrated an improved accuracy, precision repeatability and reproducibility of the estimates using the DS. The scale is appropriate, useful and reliable to visually estimate with the ABS severity in tangerine leaves.

Genetic diversity and aggressiveness of Calonectria pteridis in Eucalyptus spp.

Calonectria leaf blight, caused by Calonectria pteridis, is currently one of the main foliar diseases in eucalypt plantations in Brazil. In warm and high rainfall regions, the disease can be a limiting factor for eucalypt production when planting susceptible genotypes. The most effective method for controlling this disease in the field is the use of resistant genotypes, which requires knowledge of the genetic variability and aggressiveness of the pathogen population for effective deployment of plant resistance. This work evaluated the genetic diversity and aggressiveness of C. pteridis populations obtained from infected eucalypt plants in Monte Dourado (Pará state) and Imperatriz (Maranhão state), Brazil. To study the genetic diversity, 16 ISSR primers were tested, five of which amplified polymorphic, reproducible and informative bands. Thirty‐one closely related genotypes were identified from 84 isolates studied, indicating that the population has a low genetic diversity. The aggressiveness of seven isolates, selected according to geographic origin and their clustering in the ISSR‐based dendogram, was determined by inoculation of a hybrid Eucalyptus grandis × E. urophylla clone under controlled conditions. Disease severity was assessed by both measuring the percentage of plant defoliation and assigning a score according to a diagrammatic scale of symptoms. A high correlation between the two evaluation methods was observed, which revealed significant differences in aggressiveness among the isolates. The diagrammatic scale is recommended for disease evaluation because results are obtained much faster, before the occurrence of severe defoliation. No correlation between clustering in the ISSR‐based phylogenetic analysis and aggressiveness was observed.

Evaluation of App-Embedded Disease Scales for Aiding Visual Severity Estimation of Cercospora Leaf Spot of Table Beet.

Two diagrammatic ordinal scales are available in the Estimate app (2017 version) for Cercospora leaf spot (CLS) severity on table beet: 10% linear (linear-based diagrammatic scale [LIN]) and logarithmic based (Horsfall-Barratt [HB]). These allow for estimating severity data of four types depending on the system used. A group of 30 raters assigned percentage severity on 30 photographs of diseased table beet leaves during five rounds first without an aid and then using each of the four rating systems in Estimate. In two, the perceived ordinal score of the HB or LIN scale was assigned where severity of the subject fit best. HB2 and LIN2 involved a second choice of unitary severity within the perceived score interval. There was large variation in unaided ability of raters to estimate severity: 13% were accurate (Lin's concordance correlation [LCC] > 0.9), 23% were inaccurate (LCC < 0.7), and the remaining had moderate accuracy. Larger disparities between assigned and actual ordinal scores (mostly overestimates) occurred using the LIN compared with the HB. The LIN2 produced the most accurate estimates (Lin's concordance correlation coefficient, ρc = 0.96; generalized bias parameter, Cb = 0.99; Pearson's correlation coefficient r = 0.95) and the greatest interrater reliability (overall concordance correlation coefficient and intraclass correlation coefficient > 0.93). The two-step process using the 10% linear scale is recommended for severity estimates of CLS in table beet.

SELECTION OF COFFEE PROGENIES WITH LARGE BEANS RESISTANT TO RUST AND CERCOSPORA LEAF SPOT

&lt;p&gt;Rust is the main disease of coffee. Recently, cercospora leaf spot has grown in importance, intensifying defoliation and decreasing grain yield. The aim of this study was to use a mixed model approach to select the best progenies of "Big Coffee VL" for resistance to rust and cercospora leaf spot. We used 12 progenies with high bean yields. Based on bean size, leaves and plant size, plants within each progeny were classified as "small" (P), "medium" (M) and "large" (G). The experimental design was completely randomized, with six replicates and one plant per plot. Six measurements were carried out every 15 days for each plant by selecting 20 fully exposed leaves with higher and lower sun exposures. The measurements summarized disease severity using two diagrammatic scales to obtain the area of the leaf under rust or Cercospora leaf spot. A mixed model approach was used to calculate genotypic value (GV) and heritability estimates. The Mulamba and Mock index was used to select the most resistant progenies, in which the sum of rankings was weighted by a heritability value. Five progenies were selected; three progenies were G (G17, G9, and G12), one progeny was M (M5) and another progeny P (P23). Among these, M5 and P23 progenies are the most productive and may have potential use in future studies. The statistical approach used to predict promising genotypes facilitates the selection of genetically superior individuals for maximizing yields.&lt;/p&gt;

Resistance of the wild tomato Solanum habrochaites to Phytophthora infestans is governed by a major gene and polygenes.

This work aimed to study the inheritance of resistance to Phytophthora infestans in tomato plants, using the maximum likelihood estimation function. The susceptible cultivar Santa Clara (Solanum lycopersicum) was used as the female genitor and the P. infestans resistant S. habrochaites f. glabratum accession (BGH 6902) as the male genitor. F1 plants from the crossing were self-pollinated to produce F2 progenies, and also backcrossed with PR and PS to produce BC1:R and BC1:S generations, respectively. The tomato plants were inoculated 50 days after transplanting. Disease severity was evaluated via a diagrammatic scale. Comparison of the genetic models created using the maximum likelihood function revealed that the inheritance of resistance to P. infestans in S. habrochaites is conferred by a major gene with additive and dominance effects, polygenes with additive effects, plus the environmental effect. Vertical resistance can be explored using genes with major effects. Programs of recurrent and maker-assisted selection are considered efficient strategies with which to select genotypes that hold P. infestans resistance conferred by polygenes.

A diagramatic scale to quantify severity of antracnose in Rubus glaucus Benth

ABSTRACT: Rubus glaucus Benth, commonly referred to as mora de Castilla, is affected by Colletotrichum acutatum, as it induces anthracnose in many of the plant organs. Generally, it affects the fruits during the post-harvest phase and damages them, causing economic losses due to the poor crop quality. At present, no standardized methods are available for this pathosystem that can be used to characterize quantitatively the epidemic and to permit the prediction and comparison of the disease management techniques. In this research, we proposed a logarithmic diagrammatic scale of the severity of anthracnose induced by C. acutatum in the fruits of the thornless variety of R. glaucus Benth. This scale is constructed on the adjustment of the Weber-Fechner law and includes six classes, viz., 0%, 1-6%, 7-25%, 26-50%, 51-75%, 76-100%. The scale was validated using 14 evaluators, which entailed measuring the affected fruits with and without utilizing the scale; this improved the precision, accuracy and reproducibility of the calculations whenever the scale was used. We concluded that the scale proposed can be used to assess the severity of anthracnose induced by the fungus in the R. glaucus Benth fruits.

Development and validation of diagrammatic scale to assess target spot severity in cotton

Due to the emergence of target spot disease on cotton, caused by the fungus Corynespora cassiicola, the aim of this study was the development and validation of a diagrammatic scale to assess the severity of target spot on cotton leaves using Lin’s statistic and linear regression models. For the design of the scale, 200 cotton leaves were collected from naturally infected plants. Severity was measured by APS assess image analysis software. The diagrammatic scale was developed with seven levels of severity: 1%, 2%, 5%, 9%, 19%, 37 and 53%. Validation was determined by severity estimates of 50 leaves by five experienced and five inexperienced evaluators. The first assessment was performance without a scale and the second with a scale aid. The data were analyzed by two methods: Lin’s statistics and linear regression. The diagrammatic scale aid reduced the absolute and relative error and improved precision (R2 = 0.79 and 0.91 without and with the scale, respectively). Evaluators overestimated the severity without the scale. Agreement (Lin’s concordance correlation coefficient, pc = 0.83 and 0.94, without and with the scale, respectively) and accuracy (Bias correction factor, Cb = 0.93 and 0.98, without and with the scale, respectively) were improved with the scale. The agreement between experience evaluators was higher with the scale. The use of the proposed diagrammatic scale contributed to assessment of target spot in cotton leaves by improving inter- and intra-rater reliability and accuracy of experienced and inexperienced evaluators.

Elaboration and validation of diagrammatic scale for lettuce powdery mildew

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.

Escala diagramática para cuantificación de la severidad de la roya en hojas de teca

&lt;p&gt;La roya de la teca (&lt;em&gt;Tectona grandis&lt;/em&gt;), causada pelo fungo &lt;em&gt;Olivea tectonae&lt;/em&gt;, se ha presentado en varias regiones de Brasil en casos graves que conducen a la caída prematura de las hojas e incluso la muerte de la planta. Sin embargo, todavía no existe un método estándar para la evaluación de la severidad de la enfermedad en el campo. El objetivo de este estudio fue desarrollar y validar una escala diagramática para cuantificar la severidad de la roya en hojas de teca. La escala diagramática se desarrolló en función de la severidad de la enfermedad que abarca 0, 2.5, 5, 10, 20, 40 y 80% del área foliar con síntomas de roya. La escala fue validada por 10 evaluadores, que analizaron 50 hojas con un rango de severidad de la enfermedad, sin y con escala diagramática como ayuda de evaluación. Los evaluadores presentaron diferencias en la percepción de los niveles de severidad de la enfermedad. Con la adopción de la escala diagramática todos los evaluadores mejoraron la precisión de las estimaciones, hubo reducción en los errores absolutos y buenas estimaciones de repetitividad. La escala diagramática propuesta es adecuada para la evaluación de la severidad de la roya en las hojas de teca, siendo capaz de proporcionar precisión y repetitividad das estimativas.&lt;/p&gt;

Effectiveness of different fungicide formulations and number of applications in controlling wheat leaf rust

ABSTRACT Leaf rust (Puccinia triticina) is one of the most common diseases in wheat crops. For effective control of such disease, leaf application of mixtures of triazole and strobilurin fungicides is recommended. The aim of this study was to evaluate the efficacy of different fungicide formulations and numbers of applications in controlling wheat leaf rust in the cultivar TBIO Pioneiro 2010. Experimental design was completely randomized, 2x2 factorial arrangement, consisting of two fungicide formulations and two numbers of applications, as well as four replicates. Treatments were: azoxystrobin + tebuconazole, three and four applications; trifloxystrobin + prothioconazole, three and four applications; and a control treatment without fungicide application. For treatments with three applications, fungicides were applied at the phenological stages of: elongation, booting and flowering. For treatments with four applications, fungicides were applied at the phenological stages of: tillering, elongation, booting and flowering. The efficiency of fungicides on leaf rust control was analyzed based on the disease severity assessment by calculating the Area Under Disease Progress Curve (AUDPC). Severity data were obtained based on percentage scores of leaf area with visible disease symptoms/signs according to Cobb’s diagrammatic scale. Fungicides with azoxystrobin + tebuconazole and trifloxystrobin + prothioconazole showed efficient control of wheat leaf rust (higher than 85%). For yield components, there was no statistical difference between numbers of applications, but there was a statistical difference between fungicide formulations, except for grain yield. Furthermore, for yield components, all fungicide treatments significantly differed from control.

Diagrammatic scale of severity for postharvest black rot (Ceratocystis paradoxa) in coconut palm fruits

ABSTRACT One of the major bottlenecks in the postharvest commercialization of coconut fruits is the black rot disease, caused by the fungus Ceratocystis paradoxa. This disease has been neglected in the main production areas or associated with other coconut diseases. To date, there are no standardized methods for assessing the intensity of such a problem. In this sense, the aim of our study was to prepare and validate a diagrammatic scale to evaluate the disease severity in coconut fruits. We also tested the scale applicability comparing distinct C. paradoxa isolates on inoculated fruits. For such quantification, the fruit longitudinal sectioning was necessary, allowing the visualization of internal symptoms. The proposed scale showed good repeatability and high reproducibility, with absolute errors around 8%, while the coefficient of determination presented an average of 91% with the aid of the scale and of 59% without the scale. In addition, symptom analyses showed that the outer necrosis does not match the internal damage. Therefore, we suggest in this study that the severity estimate of this disease be obtained by using the presented scale.

Diagrammatic scale for assessing foliar symptoms of alternaria brown spot in citrus

Alternaria brown spot (ABS) is the main fungal disease of mandarins. Cause damage to fruits, branches and leaves. For determinations of disease severity in fruit, there is a specific diagrammatic scale, which does not occur for foliar lesions. In order to standardize leaf reviews of ABS in citrus, a diagrammatic scale was developed from the collection of symptomatic Dancy tangerine and Murcott tangor leaves, with ten levels, from zero to 97% of the area damaged by the pathogen. They were tested by five evaluators who analyzed 100 pictures of symptomatic leaves with and without the use of the proposed scale. To validate the scale, precision and accuracy of assessors in rating the images were compared. Results showed that the use of the scale improved the accuracy of the evaluators, with increased accuracy. This shows that the leaf scale can be used to determine the severity of alternaria brown spot in citrus.

Influence of fruit age of the Brazilian Green Dwarf coconut on the relationship between Aceria guerreronis population density and percentage of fruit damage.

The coconut mite, Aceria guerreronis Keifer (Acari: Eriophyidae), is one of the main coconut pests in the American, African and parts of the Asian continents, reaching densities of several thousand mites per fruit. Diagrammatic scales have been developed to standardize the estimation of the population densities of A. guerreronis according to the estimated percentage of damage, but these have not taken into account the possible effect of fruit age, although previous studies have already reported the variation in mite numbers with fruit age. The objective of this study was to re-construct the relation between damage and mite density at different fruit ages collected in an urban coconut plantation containing the green dwarf variety ranging from the beginning to nearly the end of the infestation, as regularly seen under field conditions in northeast Brazil, in order to improve future estimates with diagrammatic scales. The percentage of damage was estimated with two diagrammatic scales on a total of 470 fruits from 1 to 5months old, from a field at Ilhéus, Bahia, Brazil, determining the respective number of mites on each fruit. The results suggested that in estimates with diagrammatic scales: (1) fruit age has a major effect on the estimation of A. guerreronis densities, (2) fruits of different ages should be analyzed separately, and (3) regular evaluation of infestation levels should be done preferably on fruits of about 3-4months old, which show the highest densities.