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.

scholarly journals Effective Biomass Reduction of the Invasive Weed Species Banana Poka by Septoria Leaf Spot

Plant Disease ◽  
2001 ◽  
Vol 85 (4) ◽  
pp. 357-361 ◽  
Author(s):  
Eduardo E. Trujillo ◽  
Chris Kadooka ◽  
Victor Tanimoto ◽  
Steve Bergfeld ◽  
Glenn Shishido ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Severe Disease ◽  
Disease Spread ◽  
Leaf Spot Disease ◽  
Native Forest ◽  
Invasive Weed ◽  
Disease Epidemics ◽  
Biomass Reduction ◽  
Septoria Leaf Spot

Inoculations of Septoria passiflorae for biological control of banana poka (Passiflora tripartita var. tripartita) at different forest sites in Hawaii, Kauai, and Maui resulted in successful establishment of the Septoria leaf spot disease at all sites during 1996. Semi-annual monitoring of sites in 1997 revealed low disease incidence and no disease spread to adjacent non-inoculated plants. Site inspections in March 1998 revealed light disease epidemics causing visible defoliation at inoculated sites on Kauai and Maui. Banana poka biomass reduction at sites with light epidemics of the disease in Kauai and Maui were estimated to be less than 10% in 1998, whereas in 1999 biomass reduction ranged from 50 to 95%. Five of 11 inoculation sites in 1996 on the island of Hawaii showed no disease. These five sites on Kaloko had frequent acid rainfall averaging 3.2 pH, which inhibited spore germination and infection. Six sites, free of acid rain, three at Hilo Forest Reserve and three at Puuwaawaa Wildlife Sanctuary, had severe disease epidemics by 1998, and vine defoliation was >90%. Widespread epidemics of the disease occurred in 1999, resulting in estimated 80 to 95% biomass reductions in more than 2,000 hectares of native forest infested with banana poka.

Dark leaf spot (Alternaria brassicicola) on Chinese cabbage: temporal spread and its influencing factors

2002 ◽  
Vol 53 (10) ◽  
pp. 1095 ◽  
Author(s):  
L. Y. Chen ◽  
T. V. Price
Keyword(s):  
Chinese Cabbage ◽  
Wind Direction ◽  
Leaf Spot ◽  
Irrigation System ◽  
Disease Incidence ◽  
Field Trials ◽  
Alternaria Brassicicola ◽  
Disease Spread ◽  
Average Wind ◽  
Temporal Spread

Temporal spread of dark leaf spot on Chinese cabbage was studied in experimental plots for 2 years. The effect of row orientation, the orientation of inoculated plants, and irrigation system on disease incidence and the effect of average wind direction on disease spread were investigated. A line source of inoculum in each plot was used for the 1993–94 summer and the 1994 spring–summer field trials, and 3 line sources for a 1995 autumn field trial. Disease progressed more rapidly in the 1993–94 summer than in the 1995 autumn. Disease epidemic did not develop in the 1994 spring–summer when environmental conditions were unfavourable. Disease incidence was higher in plots with row orientation parallel to the average wind direction than in plots with row orientation at right angles to the average wind direction for both the 1993–94 summer and the 1995 autumn trials. In summer 1993–94, across-row inoculation resulted in higher disease incidence than row inoculation did. No difference in disease incidence occurred between channel irrigation and overhead irrigation plots. Secondary infections always occurred adjacent to the source of inoculum and disease spread was influenced by the prevalent wind direction.

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 Angular Leaf Spot of Cucumber Caused by Pseudomonas syringae pv. lachrymans in Kurdistan

Plant Disease ◽  
2007 ◽  
Vol 91 (6) ◽  
pp. 769-769 ◽  
Author(s):  
B. Harighi
Keyword(s):  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Biochemical Characterization ◽  
Protein Pattern ◽  
Disease Incidence ◽  
Angular Leaf Spot ◽  
Cell Protein ◽  
Fluorescent Pseudomonad ◽  
Cucumis Sativus L ◽  
Production Of Hydrogen

During the spring of 2004 and 2005, angular leaf spot was observed on cucumber (Cucumis sativus L.) in some areas of Kurdistan Province in Iran for the first time. Disease incidence in affected fields was approximately 100%. Symptoms were initially small, round or irregular, water-soaked spots on leaves ranging from 3 to 5 mm in diameter. These spots were limited by the leaf veins that gave them an angular appearance. Under humid conditions, tiny, white exudates formed on the undersides of the leaves and severely infected leaves turned yellow. A fluorescent pseudomonad was consistently isolated from lesions on King's medium B and characterized. Twelve strains were selected from Marivan, Dehgolan and Kamyaran in western Iran. When compared with previously identified strains, (1,2) on the basis of phenotypic, biochemical, and physiological properties, isolates were identified as Pseudomonas syringae pv. lachrymans. This was confirmed with data from whole-cell protein pattern analysis, which indicated that the strains were highly similar to reference strain 4963T (International Collection of Microorganism from Plants [ICMP]). Isolates produced round, white colonies that were 1 to 2 mm in diameter. All strains were gram negative, aerobic, levan positive, oxidase negative, potato soft rot negative, arginine dihydrolase negative, and induced a hypersensitive response on tobacco leaves. The strains were positive for catalase, urease, and 4% NaCl tolerance and negative for nitrate reduction, methyl red production, acetoin and indole production, phosphatase, gas from glucose, reducing substances from sucrose, and ketolactose tests. All strains hydrolyzed Tween 80, esculin, casein, and gelatin, but failed to hydrolyze starch and lecithin. Results for growth at 41°C and production of hydrogen sulfide from cystein and peptone were negative. In Ayers' medium, all strains produced acid from d-galactose, citrate, sucrose, raffinose, fructose, d-xylose, glucose, inositol, mannitol, sorbitol, glycerin, mannose, ribose but not from trehalose, maltose, salicin, l-rhamnose, adonitol, cellobiose, ethanol, l-sorbose, inulin, dulcitol, starch, lactose or melibiose. All strains used l-asparagine, l-lysine, aspartate and l-arginine but did not use l-tartrate, propionate, ornithine, l-tyrosine, borate, benzoate, l-tryptophan, or acetate as carbon sources. Pathogenicity of four strains was confirmed by injecting bacterial suspensions (108 CFU/ml) into the undersides of 3- to 4-week-old cucumber leaves using a sterile syringe. Sterile water was injected into cucumber leaves as a negative control. Inoculated plants were maintained in the greenhouse at 25 to 28°C with 90 to 98% relative humidity until symptoms were assessed 4 to 7 days after inoculation. Angular leaf lesions developed on inoculated cucumber. Bacterial strains were reisolated from infected tissues and confirmed as P. syringae pv. lachrymans by biochemical characterization as previously described. This disease has been observed in other areas of Iran, but to our knowledge, this is the first report that characterizes the phenotypic and biochemical properties of the bacterium and disease in Kurdistan Province. References: (1) D. J. Brenner et al. Bergy's Manual of Systematic Bacteriology. 2nd ed. Springer, New York, NY, 2005. (2) D. C. Sands et al. J. Bacteriol. 101:9, 1970.

scholarly journals First Report of Xanthomonas fragariae Causing Angular Leaf Spot on Strawberry Plants in México

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 682-682 ◽  
Author(s):  
S. P. Fernández-Pavía ◽  
G. Rodríguez-Alvarado ◽  
E. Garay-Serrano ◽  
R. Cárdenas-Navarro
Keyword(s):  
Leaf Spot ◽  
Pathogenic Bacteria ◽  
Disease Incidence ◽  
Angular Leaf Spot ◽  
Pcr Analysis ◽  
Bacterial Suspension ◽  
American Phytopathological Society ◽  
First Report ◽  
Leaf Surfaces ◽  
Xanthomonas Fragariae

The state of Michoacán is the most important strawberry producer in México. During January 2007, field-grown strawberry plants cv. Aromas showing vein necrosis were observed in 3 ha in Zamora County, in fruit production fields. The average disease incidence in the field was 80%. Infected plants presented water-soaked lesions limited by veins on the lower leaf surfaces, which enlarged to form angular spots (1). Additionally, most affected plants presented severe necrosis in the main veins and reddish to necrotic lesions on the upper leaf surfaces. Gram-negative bacteria were consistently isolated from leaves with water-soaked lesions. Isolated bacteria produced mucoid, yellow colonies on YDC, grew on tween and nutrient agar (NA), but not on SX media. Strains produced non-fluorescent colonies on King's B media, were positive starch hydrolysis, negative esculin hydrolysis; and produced acid from fructose but not from arabinose, galactose, celobiose, and trehalose. Growth was inhibited by 2% NaCl (3). Indirect ELISA analysis (NEOGEN, Lansing, MI) was conducted using antibodies specific for Xanthomonas fragariae. Conventional PCR assay using the primer pairs 241A/241B was performed (2). The ELISA test was positive. The expected 300- and 550-bp bands were observed in the PCR analysis. The bacteria was identified as X. fragariae Kennedy and King. Pathogenicity tests were conducted twice in a greenhouse (24 ± 4°C) on a total of five strawberry cv. Aromas plants. The main vein of each of three leaves per plant were punctured using sterile needles. Pathogen inoculum was obtained from 6- to 8-day-old NA cultures. Bacteria were applied onto the wounds with a sterile cotton swab dipped into the bacterial suspension (105 CFU/ml). Inoculated plants were covered with plastic bags for 48 h. Symptoms resembling those seen in the field developed on all inoculated plants after 9 days. X. fragariae was re-isolated from the necrotic lesions and identified by PCR. Control plants were similarly inoculated with water but did not develop symptoms. To our knowledge, this is the first report of X. fragariae causing angular leaf spot in strawberry in Michoacán, México. References: (1) J. L. Maas, ed. Compendium of Strawberry Diseases. The American Phytopathological Society, St. Paul, MN, 1998. (2) M. R. Pooler et al. Appl. Environ. Microbiol. 62:3121, 1996. (3) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.

scholarly journals Effect of fungicide on disease incidence and yield of bean (Phaseolus vulgaris L.) infected with Isariopsis griseola Sacc. and Ascochyta phaseolorum Sacc.

1969 ◽  
pp. 127-134
Author(s):  
Rocío Rodríguez ◽  
Pedro L. Meléndez
Keyword(s):  
Phaseolus Vulgaris ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Angular Leaf Spot ◽  
Leaf Spot Disease ◽  
Phaseolus Vulgaris L ◽  
Foliar Diseases ◽  
Spot Disease

Two foliar diseases of beans, Phaseolus vulgaris L., namely angular leaf spot and ascochyta leaf spot, caused by Isariopsis griseola and Ascochyta phaseolorum, respectively, were effectively controlled with chemicals. Biweekly applications of mancozeb and chlorothalonil (1.12, 2.48 and 4.48 kg/ ha) effectively protected the foliage of bean cultivars Bonita and Naranjito against attacks by both pathogens. Cultivar Bonita responded better to treatments than cv. Naranjito in terms of yield. Some dosages of mancozeb and chlorothalonil increased yield of cv. Bonita affected by angular leaf spot. Yield increases in plots treated with benomyl increased only when the highest rate of this chemical was used. Even at the lowest dosages, the three chemicals tested increased yield in cv. Bonita affected by the ascochyta leaf spot disease.

scholarly journals Finished Genome Sequences of Xanthomonas fragariae , the Cause of Bacterial Angular Leaf Spot of Strawberry

2016 ◽  
Vol 4 (6) ◽  
Author(s):  
Peter M. Henry ◽  
Johan H. J. Leveau
Keyword(s):  
Leaf Spot ◽  
Angular Leaf Spot ◽  
Northern California ◽  
Strawberry Fruit ◽  
Genome Sequences ◽  
Xanthomonas Fragariae ◽  
Foliar Pathogen ◽  
Nursery Production ◽  
Long Read ◽  
Field Production

Xanthomonas fragariae is a foliar pathogen of strawberry that is of significant concern to nursery production of strawberry transplants and field production of strawberry fruit. Long-read sequencing was employed to generate finished genomes for two isolates (each with one chromosome and two plasmids) from symptomatic plants in northern California.

Dark leaf spot (Alternaria brassicicola) on Chinese cabbage: spatial patterns

2005 ◽  
Vol 56 (7) ◽  
pp. 699 ◽  
Author(s):  
L. Y. Chen ◽  
T. V. Price ◽  
M. J. Silvapulle
Keyword(s):  
Chinese Cabbage ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Field Trials ◽  
Alternaria Brassicicola ◽  
Disease Spread ◽  
Distance Class ◽  
Maximum Information ◽  
Spatial Spread ◽  
Core Cluster

The spatial spread of dark leaf spot caused by Alternaria brassicicola on Chinese cabbage was characterised over 2 years. The study was conducted in 2 field trials using ordinary runs, mapping, spatial autocorrelation, and 2-dimensional distance class analyses. Diseased plants were generally clustered and cluster orientation coincided with the line of inoculation. Disease spread was greater within than across rows. The maximum number of spatial lags with significantly positive autocorrelations occurred when disease incidence levels reached 20–80% in summer 1993–94. Core cluster size generally increased with disease incidence. Two-dimensional distance class analysis was the best analytical method among those used in describing spatial spread of the disease as it did not only provide maximum information but also considered missing data.

scholarly journals Heat Treatment Effects on Strawberry Plant Survival and Angular Leaf Spot, Caused by Xanthomonas fragariae, in Nursery Production

Plant Disease ◽  
2009 ◽  
Vol 93 (3) ◽  
pp. 299-308 ◽  
Author(s):  
William W. Turechek ◽  
Natalia A. Peres
Keyword(s):  
Heat Treatment ◽  
Leaf Spot ◽  
Plant Protection ◽  
Angular Leaf Spot ◽  
Bacterial Cells ◽  
Heat Treated ◽  
Nursery Stock ◽  
Xanthomonas Fragariae ◽  
Nursery Production ◽  
Plastic Bag

Angular leaf spot is an important disease in strawberry nursery production. The European and Mediterranean Plant Protection Organization (EPPO) lists Xanthomonas fragariae as an A2 quarantine pathogen. Therefore, nurseries wishing to export plants to European countries must maintain phytosanitary standards to exclude X. fragariae. To help nurseries achieve these standards, heat treatment for killing or reducing the number of viable bacterial cells in strawberry crown tissue was investigated. First, the sensitivity of bacteria to heat was determined by dispensing 1-ml aliquots of standardized cell suspensions in microcentrifuge tubes for each of four isolates of X. fragariae, including the type culture, and submerging the tubes in water at 36, 40, 44, 48, 52, and 56°C for 0, 1, 2.5, 5, 10, 15, 30, 60, 120, 240, 360, and 480 min. Bacteria were transferred to growth medium to determine the proportion surviving heat treatment. Two trials were conducted in a greenhouse to determine the sensitivity of bare-root plants to heat treatment. In the first trial, plants of cvs. Camarosa and Diamante from two different nurseries were heat treated as follows: (i) plants placed in metallic mesh cages and immersed directly into water (industry standard, direct dip); (ii) plants sealed in a plastic bag and the bag immersed in water (bagged dry); or (iii) plants wetted in warm water, sealed in a plastic bag, and then immersed in water (bagged wet). Plants were treated at 44 or 48°C for 0, 60, 120, 180, and 240 min. In the second trial, plants of cvs. Camarosa, Camino Real, Diamante, Oso Grande, Strawberry Festival, and Ventana from a single nursery were subjected to the same treatments. In both trials, plants were potted after treatment and rated for growth characteristics. Results showed that populations of bacteria exposed to 56 and 52°C were killed completely after 15 and 60 min of exposure, respectively; both treatments killed plants. Bacterial populations exposed to 44°C for 4 h or 48°C for 2 h were reduced by 105 or 106 CFU/ml. The same treatments minimally affected vegetative growth of plants bagged dry or wet, but flowering was adversely affected. These heat treatments were selected for testing of nursery stock of several cultivars in field trials established at two locations in successive years. The survival rate among cultivars was similar to that observed in greenhouse trials, and angular leaf spot developed appreciably only in non-heat-treated control plots. Heat treatment of strawberry nursery stock is feasible and can be used to supplement standard production practices for producing pathogen-free nursery stock.

scholarly journals Spatial Pattern Analysis of Strawberry Leaf Blight in Perennial Production Systems

1999 ◽  
Vol 89 (5) ◽  
pp. 421-433 ◽  
Author(s):  
W. W. Turechek ◽  
L. V. Madden
Keyword(s):  
Spatial Pattern ◽  
Disease Incidence ◽  
Spatial Association ◽  
Disease Status ◽  
Leaf Blight ◽  
Data Sets ◽  
Ratio Test ◽  
Spatial Pattern Analysis ◽  
Test Statistic ◽  
Degree Of Heterogeneity

Spatial pattern of the incidence of strawberry leaf blight, caused by Phomopsis obscurans, was quantified in commercial strawberry fields in Ohio using statistics for heterogeneity and spatial correlation. For each strawberry planting, two transects were randomly chosen and the proportion of leaflets (out of 15) and leaves (out of five) with leaf blight symptoms was determined from N = 49 to 106 (typically 75) evenly spaced sampling units, thus establishing a natural spatial hierarchy to compare patterns of disease. The beta-binomial distribution fitted the data better than the binomial in 92 and 26% of the 121 data sets over 2 years at the leaflet and leaf levels, respectively, based on a likelihood ratio test. Heterogeneity in individual data sets was measured with the index of dispersion (variance ratio), C(α) test, a standard normal-based test statistic, and estimated θ parameter of the beta-binomial. Using these indices, overdispersion was detected in approximately 94 and 36% of the data sets at the leaflet and leaf levels, respectively. Estimates of the slope from the binary power law were significantly (P < 0.01) greater than 1 and estimates of the intercept were significantly greater than 0 (P < 0.01) at both the leaflet and leaf levels for both years, indicating that degree of heterogeneity was a function of incidence. A covariance analysis indicated that cultivar, time, and commercial farm location of sampling had little influence on the degree of heterogeneity. The measures of heterogeneity indicated that there was a positive correlation of disease status of leaflets (or leaves) within sampling units. Measures of spatial association in disease incidence among sampling units were determined based on autocorrelation coefficients, runs analysis, and a new class of tests known as spatial analysis by distance indices (SADIE). In general, from 9 to 22% of the data sets had a significant nonrandom spatial arrangement of disease incidence among sampling units, depending on which test was used. When significant associations existed, the magnitude of the association was small but was about the same for leaflets and leaves. Comparing test results, SADIE analysis was found to be a viable alternative to spatial autocorrelation analysis and has the advantage of being an extension of heterogeneity analysis rather than a separate approach. Collectively, results showed that incidence of Phomopsis leaf blight was primarily characterized by small, loosely aggregated clusters of diseased leaflets, typically confined within the borders of the sampling units.

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