scholarly journals Spatiotemporal Analysis of Spread of Infections by Verticillium dahliae Pathotypes Within a High Tree Density Olive Orchard in Southern Spain

2008 ◽  
Vol 98 (2) ◽  
pp. 167-180 ◽  
Author(s):  
J. A. Navas-Cortés ◽  
B. B. Landa ◽  
J. Mercado-Blanco ◽  
J. L. Trapero-Casas ◽  
D. Rodríguez-Jurado ◽  
...  
Keyword(s):  
Verticillium Dahliae ◽  
Binary Data ◽  
Disease Incidence ◽  
Spatial Association ◽  
Spatiotemporal Analysis ◽  
Southern Spain ◽  
Cotton Field ◽  
Point Pattern ◽  
Olive Orchard ◽  
Over Time

The development of Verticillium wilt epidemics in olive cv. Arbequina was studied from November 1999 to May 2003 in a drip-irrigated, nontillage orchard established in a soil without a history of the disease at Córdoba, southern Spain. Disease incidence measured at 1-month-intervals increased from 0.2 to 7.8% during this period. Verticillium dahliae infecting the trees was characterized as defoliating (D) or nondefoliating (ND) pathotypes by a specific, multiplex-polymerase chain reaction (PCR) assay. Of the symptomatic trees, 87.2 and 12.8% were infected by the D or ND pathotypes, respectively. Dynamics of disease incidence were described by a generalized logistic model with a multiple sigmoid pattern. In the fitted model, the infection rate was highest in the winter to spring period and decreased to minimum values in the summer to fall period. Binary data of disease incidence was analyzed for point pattern and spatial correlation, either directly or after parsing them in contiguous quadrats. Overall, ordinary runs analysis indicated a departure from randomness of disease within rows. The binomial index of dispersion, interclass correlation, and Taylor's power law for various quadrat sizes suggested aggregation of diseased trees within the quadrat sizes tested. Spatial analysis by distance indices showed a nonrandom arrangement of quadrats containing infected trees. Spatial pattern was characterized by the occurrence of several clusters of infected trees. Increasing clustering over time was generally suggested by stronger values of clustering index over time and by the increase in the size of patch clusters. Significant spatial association was found in the clustering of diseased trees over time across cropping seasons; however, clustering was significant only for infections by D V. dahliae, indicating that infections by the D pathotype were aggregated around initial infections. The number and size of clusters of D V. dahliae-infected trees increased over time. Microsatellite-primed PCR assays of a representative number of V. dahliae isolates from diseased trees indicated that the majority of infecting D isolates shared the fingerprinting profile with D V. dahliae isolated from soil of a naturally infested cotton field in close proximity to the orchard, suggesting that short distance dispersal of the pathogen from this soil to the olive orchard may have occurred.

scholarly journals Analysis of the Spatial Pattern of Strawberry Angular Leaf Spot in California Nursery Production

2017 ◽  
Vol 107 (10) ◽  
pp. 1243-1255 ◽  
Author(s):  
Christophe Gigot ◽  
William Turechek ◽  
Neil McRoberts
Keyword(s):  
Spatial Pattern ◽  
Leaf Spot ◽  
Management Practices ◽  
Disease Incidence ◽  
Spatial Association ◽  
Angular Leaf Spot ◽  
Disease Spread ◽  
Point Pattern ◽  
Common Disease ◽  
Nursery Production

In California, angular leaf spot (ALS) is a common disease in strawberry nursery production, and a major concern for nurseries wishing to export plants. As the spatial pattern of a disease can offer insight into pathogen source, mode of dissemination, and how current crop management practices affect epidemic development, an understanding of the spatial pattern of ALS would allow nursery growers to make informed decisions regarding disease management. Ninety-seven field assessments of disease incidence were performed at different nursery locations in 2014 and 2015 to quantify ALS spatial pattern under commercial conditions. Both point-pattern and geostatistical statistical procedures were used to analyze the data. The spatial pattern of ALS was characterized by a high degree of heterogeneity, as indicated by high median values of the beta-binomial distribution’s theta parameter (0.643), and the index of dispersion, D (4.218). The binary power law provided a robust description of the data with estimated slope and intercept parameters significantly greater than 1 and 0, respectively (P < 0.001). Spatial analysis by distance indices (SADIE) detected significant nonrandom spatial arrangements for 64% of the data sets. Analysis of directional disease spread showed a strong spatial association between sampling units along the same planting row. This suggests that recurrent crop operations during the growing season play a significant role in ALS spread and should be taken into account to improve disease control.

Changing Trends in Age and Sex Distributions of Lyme Disease—United States, 1992-2016

2021 ◽  
pp. 003335492110267
Author(s):  
Kiersten J. Kugeler ◽  
Paul S. Mead ◽  
Amy M. Schwartz ◽  
Alison F. Hinckley
Keyword(s):  
United States ◽  
Lyme Disease ◽  
Disease Incidence ◽  
Age Distribution ◽  
Relative Size ◽  
The United States ◽  
Male Predominance ◽  
Age Related ◽  
Over Time ◽  
Age And Sex

Lyme disease is the most common vector-borne disease in the United States and is characterized by a bimodal age distribution and male predominance. We examined trends in reported cases during a 25-year period to describe changes in the populations most affected by Lyme disease in the United States. We examined demographic characteristics of people with confirmed cases of Lyme disease reported to the Centers for Disease Control and Prevention during 1992-2016 through the National Notifiable Diseases Surveillance System. We grouped cases into 5-year periods (1992-1996, 1997-2001, 2002-2006, 2007-2011, 2012-2016). We calculated the average annual incidence by age and sex and used incidence rate ratios (IRRs) to describe changes in Lyme disease incidence by age and sex over time. We converted patient age at time of illness into patient birth year to ascertain disease patterns according to birth cohorts. The incidence of Lyme disease in the United States doubled from 1992-1996 to 2012-2016 (IRR = 1.74; 95% CI, 1.70-1.78) and increased disproportionately among males; IRRs were 39%-89% higher among males than among females for most age groups. During the study period, children aged 5-9 years were most frequently and consistently affected. In contrast, the average age of adults with Lyme disease increased over time; of all adults, people born during 1950-1964 were the most affected by Lyme disease. Our findings suggest that age-related behaviors and susceptibilities may drive infections among children, and the shifting peak among adults likely reflects a probability proportional to the relative size of the baby boom population. These findings can inform targeted and efficient public health education and intervention efforts.

scholarly journals How Far Has China’s Urbanization Gone?

2018 ◽  
Vol 10 (8) ◽  
pp. 2953 ◽  
Author(s):  
Yiping Xiao ◽  
Yan Song ◽  
Xiaodong Wu
Keyword(s):  
Urban Development ◽  
Spatial Autocorrelation ◽  
Spatial Data ◽  
Spatial Association ◽  
Early Years ◽  
Spatial Data Analysis ◽  
Rapid Urbanization ◽  
Urban Rural ◽  
Global Spatial Autocorrelation ◽  
Over Time

China’s rapid urbanization has attracted wide international attention. However, it may not be sustainable. In order to assess it objectively and put forward recommendations for future development, this paper first develops a four-dimensional Urbanization Quality Index using weights calculated by the Deviation Maximization Method for a comprehensive assessment and then reveals the spatial association of China’s urbanization by Exploratory Spatial Data Analysis. The study leads to three major findings. First, the urbanization quality in China has gradually increased over time, but there have been significant differences between regions. Second, the four aspects of urbanization quality have shown the following trends: (i) the quality of urban development has steadily increased; (ii) the sustainability of urban development has shown a downward trend in recent years; (iii) the efficiency of urbanization improved before 2006 but then declined slightly due to capital, land use, and resource efficiency constraints; (IV) the urban–rural integration deteriorated in the early years but then improved over time. Third, although the urbanization quality has a significantly positive global spatial autocorrelation, the local spatial autocorrelation varies between eastern and western regions. Based on these findings, this paper concludes with policy recommendations for improving urbanization quality and its sustainability in China.

scholarly journals Coupling Disease-Progress-Curve and Time-of-Infection Functions for Predicting Yield Loss of Crops

2000 ◽  
Vol 90 (8) ◽  
pp. 788-800 ◽  
Author(s):  
L. V. Madden ◽  
G. Hughes ◽  
M. E. Irwin
Keyword(s):  
Yield Loss ◽  
Numerical Solutions ◽  
Disease Incidence ◽  
Time Interval ◽  
Short Time Interval ◽  
Time Duration ◽  
Plant Yield ◽  
Disease Progress ◽  
Time Of Infection ◽  
Over Time

A general approach was developed to predict the yield loss of crops in relation to infection by systemic diseases. The approach was based on two premises: (i) disease incidence in a population of plants over time can be described by a nonlinear disease progress model, such as the logistic or monomolecular; and (ii) yield of a plant is a function of time of infection (t) that can be represented by the (negative) exponential or similar model (ζ(t)). Yield loss of a population of plants on a proportional scale (L) can be written as the product of the proportion of the plant population newly infected during a very short time interval (X′(t)dt) and ζ(t), integrated over the time duration of the epidemic. L in the model can be expressed in relation to directly interpretable parameters: maximum per-plant yield loss (α, typically occurring at t = 0); the decline in per-plant loss as time of infection is delayed (γ; units of time-1); and the parameters that characterize disease progress over time, namely, initial disease incidence (X0), rate of disease increase (r; units of time-1), and maximum (or asymptotic) value of disease incidence (K). Based on the model formulation, L ranges from αX0 to αK and increases with increasing X0, r, K, α, and γ-1. The exact effects of these parameters on L were determined with numerical solutions of the model. The model was expanded to predict L when there was spatial heterogeneity in disease incidence among sites within a field and when maximum per-plant yield loss occurred at a time other than the beginning of the epidemic (t > 0). However, the latter two situations had a major impact on L only at high values of r. The modeling approach was demonstrated by analyzing data on soybean yield loss in relation to infection by Soybean mosaic virus, a member of the genus Potyvirus. Based on model solutions, strategies to reduce or minimize yield losses from a given disease can be evaluated.

scholarly journals High Susceptibility of Olive Cultivar FS-17 to Alternaria alternata in Southern Spain

Plant Disease ◽  
2008 ◽  
Vol 92 (8) ◽  
pp. 1252-1252 ◽  
Author(s):  
J. Moral ◽  
R. De la Rosa ◽  
L. León ◽  
D. Barranco ◽  
T. J. Michailides ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Disease Incidence ◽  
Southern Spain ◽  
Fruit Rot ◽  
Planting Density ◽  
High Susceptibility ◽  
Olive Cultivar ◽  
White Skin ◽  
Olive Cultivars ◽  
Olive Trees

Traditional olive orchards in Spain have been planted at a density of 70 to 80 trees per ha with three trunks per tree. During the last decade, the hedgerow orchard, in which planting density is approximately 2,000 trees per ha, was developed. In 2006 and 2007, we noted a severe outbreak of fruit rot in FS-17, a new cultivar from Italy, in an experimental hedgerow planting in Córdoba, southern Spain. The incidence of fruit rot in ‘FS-17’ was 80% in January of 2006 and 24% in January of 2007. Cvs. Arbosana, IRTA-i18 (a selected clone from ‘Arbequina’), and Koroneiki had no symptoms in either year of the study. Disease incidence in ‘Arbequina’ was <0.1% only in 2006. Affected fruits were soft with gray-white skin and they eventually mummified. Black-green sporodochia were observed on the surface of diseased fruits. A fungus was isolated from diseased fruits on potato dextrose agar (PDA) and incubated at 22 to 26°C with a 12-h photoperiod. After 8 days of growing on PDA, fungal colonies formed conidial chains having a main axis with up to 10 conidia and secondary and tertiary short branches with two to four conidia. Conidia were obpyriform, ovoid, or ellipsoidal, without a beak or with a short beak, had up to four transverse septa, and measured 11.7 to 24.7 (mean 19.6) μm long and 7.7 to 13.0 (mean 9.6) μm wide at the broadest part of the conidium. The length of the beak of conidia was variable, ranging from 0 to 28.6 (mean 5.5) μm. The fungus was identified as Alternaria alternata (1). Pathogenicity tests were performed by spraying 40 mature fruits of ‘FS-17’ with a spore suspension (1 × 106 spores per ml). The same number of control fruits was treated with water. After 21 days, inoculated fruit developed symptoms that had earlier been observed in the field. A. alternata was reisolated from lesions on all infected fruits. The fungus was not isolated from any of the control fruits. The experiment was performed twice. The new growing system and the high susceptibility of some olive cultivars, such as FS-17, may result in a high incidence of disease caused by a pathogen that is generally characterized as weakly virulent. To our knowledge, this is the first report of A. alternata causing a severe outbreak of fruit rot on olive trees in the field. References: (1) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002.

scholarly journals Characterization of Verticillium dahliae Isolates and Wilt Epidemics of Pepper

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 789-797 ◽  
Author(s):  
R. G. Bhat ◽  
R. F. Smith ◽  
S. T. Koike ◽  
B. M. Wu ◽  
K. V. Subbarao
Keyword(s):  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Random Amplified Polymorphic Dna ◽  
Disease Incidence ◽  
Bell Pepper ◽  
Central Coast ◽  
Minor Variation ◽  
Bell Peppers ◽  
Compatibility Group

Epidemics of Verticillium wilt in pepper fields of the central coast of California and isolates of Verticillium dahliae associated with these epidemics were characterized. The mean incidence of wilted plants per field ranged from 6.3 to 97.8% in fields with Anaheim, jalapeno, paprika, or bell peppers. In general, incidence of wilt in jalapeno and bell pepper crops was lower than in crops of other types of pepper. Inoculum density of V. dahliae in the surveyed pepper fields ranged from 2.7 to 66.6 microsclerotia g-1 dry soil, and the correlation between disease incidence and density of microsclerotia was high (r = 0.81, P < 0.01). Distribution of Verticillium wilt was aggregated in a majority of the pepper fields surveyed, but the degree of aggregation varied. Vegetative compatibility group (VCG) characterization of 67 isolates of V. dahliae indicated that 67% belonged to VCG 2, 22% to VCG 4, and 11% to a new group, designated VCG 6. The pathogenicity of isolates of V. dahliae from bell pepper and tomato plants was tested by inoculating 1-month-old bell pepper (cv. Cal Wonder) and tomato (cv. EP 7) seedlings and incubating the inoculated plants in the greenhouse. Seedlings of bell pepper were susceptible only to the isolates of V. dahliae from pepper, whereas seedlings of tomato were susceptible to both pepper and tomato isolates. Pepper isolates belonging to VCG 2, VCG 4, and VCG 6 were highly pathogenic to bell pepper and chili pepper. Temperatures between 15 and 25°C were optimal for mycelial growth of a majority of isolates of V. dahliae. Molecular characterization of pepper isolates of V. dahliae using a polymerase chain reaction (PCR)-based random amplified polymorphic DNA (RAPD) technique revealed minor variation among these isolates, but unique polymorphic banding patterns were observed for isolates belonging to VCG 6. Verticillium wilt of pepper is a major production constraint in the central coast of California. More aggressive isolates of V. dahliae may have been selected in this region as a result of intensive cropping practices.

scholarly journals 841. Implications of C. difficile Treatment on Environmental Contamination: A Randomized Controlled Trial with Microbiologic, Environmental, and Molecular Outcomes

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S11-S12
Author(s):  
Nicholas A Turner ◽  
Maria Gergen ◽  
William Rutala ◽  
Daniel J Sexton ◽  
Vance G Fowler, Jr. ◽  
...  
Keyword(s):  
Randomized Controlled Trial ◽  
Environmental Contamination ◽  
Disease Incidence ◽  
Controlled Trial ◽  
Treatment Choice ◽  
University Hospital ◽  
Hospital Environment ◽  
Secondary Outcome ◽  
Randomized Controlled ◽  
Over Time

Abstract Background Clostridioides difficile is a leading cause of healthcare-associated infection. Despite multimodal prevention efforts, in-hospital transmission continues to occur. In this study, we tested whether the choice of treatment can reduce C. difficile shedding and contamination of the inpatient environment. Methods We conducted a prospective, unblinded, randomized controlled trial of adult inpatients with C. difficile at Duke University Hospital. Thirty subjects were randomized 1:1:1 to receive metronidazole, vancomycin, or fidaxomicin. Stool specimens and environmental samples from five high-touch surfaces were serially collected throughout each subject’s hospital stay. Each specimen was assessed by quantitative culture and PCR ribotyping. Primary outcomes included the change over time in C. difficile stool burden and environmental contamination relative to treatment choice. As a secondary outcome, we examined the correlation between infecting strains and contaminating strains present in the care environment. Results Relative to metronidazole (Figure 1), C. difficile stool shedding decreased more rapidly for patients receiving vancomycin (P = 0.05) and most rapidly with fidaxomicin (P = 0.002). Treatment choice had no significant effect on total C. difficile colony counts across sites sampled over time (Figure 2). However, both vancomycin (P = 0.001) and fidaxomicin (P = 0.01) were associated with lower proportions of positive environmental cultures than metronidazole (Figure 3). Ribotyping of subjects’ stool isolates matched surrounding environmental isolates >90% of the time (Figure 4). Conclusion Fidaxomicin and vancomycin reduced C. difficile stool burden more rapidly than metronidazole. Environmental results were mixed: fidaxomicin and vancomycin were associated with fewer positive surface cultures, but no difference in total colony counts. High concordance between stool and environmental ribotypes confirms that most room contamination originated from study subjects, without a significant contribution from any additional sources. Treatment choice may have a role in reducing C. difficile contamination of the hospital environment. Further study is needed to assess for effect on disease incidence. Disclosures All Authors: No reported Disclosures.

Spatial Patterns of Microsclerotia of Verticillium dahliae in Soil and Verticillium Wilt of Cauliflower

1997 ◽  
Vol 87 (3) ◽  
pp. 325-331 ◽  
Author(s):  
C. L. Xiao ◽  
J. J. Hao ◽  
K. V. Subbarao
Keyword(s):  
Spatial Patterns ◽  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Binomial Distribution ◽  
Disease Incidence ◽  
Soil Samples ◽  
Random Pattern ◽  
Parameter Estimates ◽  
Regular Pattern ◽  
Vascular Discoloration

The spatial patterns of microsclerotia of Verticillium dahliae in soil and wilt symptoms on cauliflower were determined at three sites in each of two fields in 1994 and 1995. Each site was an 8 × 8 grid divided into 64 contiguous quadrats (2 by 2 m each). Soil samples were collected to a depth of 15 cm with a probe (2.5 cm in diameter), and samples from four sites in each quadrat were bulked. Plants in each quadrat were cut transversely, and the number of plants with vascular discoloration and the number without discoloration were recorded. The soil was assayed for microsclerotia by the modified Anderson sampler technique. Lloyd's index of patchiness (LIP) was used as an indicator to evaluate the aggregation of microsclerotia in the field. Spatial autocorrelation and geostatistical analyses were also used to assess the autocorrelation of microsclerotia among quadrats. The LIP for microsclerotia was greater than 1, indicating aggregation of propagules; however, the degree of aggregation at most sites was not high. Significant autocorrelation within or across rows was detected in some spatial autocorrelograms of propagules, and anisotropic patterns were also detected in some oriented semivariograms from geostatistical analyses for microsclerotia, indicating the influence of bed preparation in the fields on pathogen distribution. The parameter estimates p and θ in the beta-binomial distribution and the index of dispersion (D) associated with the distribution were used to assess the aggregation of diseased plants at each site. A random pattern of wilt incidence was detected at 7 of 12 sites, and an aggregated pattern was detected at 5 of 12 sites. The degree of aggregation was not high. A regular pattern of wilt severity was detected at all sites. The high disease incidence (77 to 98%) observed at 11 of the 12 sites could be explained by high inoculum density.

scholarly journals Holdover Inoculum of Pseudomonas syringae pv. alisalensis from Broccoli Raab Causes Disease in Subsequent Plantings

Plant Disease ◽  
2006 ◽  
Vol 90 (8) ◽  
pp. 1077-1084 ◽  
Author(s):  
N. A. Cintas ◽  
S. T. Koike ◽  
R. A. Bunch ◽  
C. T. Bull
Keyword(s):  
Pseudomonas Syringae ◽  
Brassica Rapa ◽  
Bacterial Blight ◽  
Laboratory Tests ◽  
Bacterial Population ◽  
Disease Incidence ◽  
Untreated Soil ◽  
Bacterial Populations ◽  
Field Soils ◽  
Over Time

Uniform plots of broccoli raab (Brassica rapa subsp. rapa) seedlings were inoculated with a rifampicin-resistant strain of Pseudomonas syringae pv. alisalensis, the causal agent of bacterial blight on crucifers, resulting in 100% disease incidence in mature plants. Diseased plants were incorporated into the soil at maturity and smaller replicated plots were replanted at various times after incorporation. Rifampicin-resistant fluorescent pseudomonads with rep-PCR profiles identical to P. syringae pv. alisalensis were isolated from lesions on plants grown in soil into which the first diseased crop was incorporated. Disease incidence declined in mature plants as the length of time between incorporation of the first planting and seeding of the replanted plots increased. Bacterial population levels in soil decreased over time and bacteria were no longer detectable 3 weeks after incorporation of the diseased crop. In laboratory tests, population levels of P. syringae pv. alisalensis decreased in untreated soil but not in autoclaved soil. Greenhouse studies demonstrated a direct correlation between population levels of P. syringae pv. alisalensis applied to soil and disease incidence in seedlings. However, the decline in bacterial populations in field soils did not wholly account for the decline in disease incidence with subsequent plantings.

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