scholarly journals Barrier effects on the spatial distribution of Xylella fastidiosa in Alicante, Spain

2021 ◽  
Author(s):  
Martina Cendoya ◽  
Ana Hubel ◽  
David Conesa ◽  
Antonio Vicent
Keyword(s):  
Host Plants ◽  
Xylella Fastidiosa ◽  
Infected Plant ◽  
Buffer Zone ◽  
Control Measures ◽  
Stationary Model ◽  
Infested Area ◽  
Posterior Mean ◽  
Spatial Range ◽  
Barrier Model

Spatial models often assume isotropy and stationarity, implying that spatial dependence is direction invariant and uniform throughout the study area. However, these assumptions are violated when dispersal barriers are present in the form of geographical features or disease control interventions. Despite this, the issue of non-stationarity has been little explored in the context of plant health. The objective of this study was to evaluate the influence of different barriers in the distribution of the quarantine plant pathogenic bacterium Xylella fastidiosa in the demarcated area in Alicante, Spain. Occurrence data from the official surveys in 2018 were analyzed with four spatial Bayesian hierarchical models: i) a stationary model representing a scenario without any control interventions or geographical features; ii) a model with mountains as physical barriers; iii) a model with a continuous or iv) discontinuous perimeter barrier as control interventions surrounding the infested area. Barriers were assumed to be totally impermeable, so they should be interpreted as areas without host plants and in which it is not possible for infected vectors or propagating plant material to pass through. Inference and prediction were performed through the integrated nested Laplace approximation methodology and the stochastic partial differential equation approach. In the stationary model the posterior mean of the spatial range was 4,030.17 m 95% CI (2,907.41, 5,563.88), meaning that host plants that are closer to an infected plant than this distance would be at risk for X. fastidiosa. This distance can be used to define the buffer zone around the infested area in Alicante. In the non-stationary models, the posterior mean of the spatial range varied from 3,860.88 m 95% CI (2,918.61, 5,212.18) in the mountain barrier model to 6,141.08 m 95% CI (4,296.32, 9,042.99) in the continuous barrier model. Compared with the stationary model, the perimeter barrier models decreased the probability of X. fastidiosa presence in the area outside the barrier. Differences between the discontinuous and continuous barrier models showed that breaks in areas with low sampling intensity resulted in a higher probability of X. fastidiosa presence. These results may help authorities prioritize the areas for surveillance and implementation of control measures.

Modeling the spatial distribution of Xylella fastidiosa. A non-stationary approach with dispersal barriers.

2021 ◽  
Author(s):  
Martina Cendoya ◽  
Ana Hubel ◽  
David V Conesa ◽  
Antonio Vicent
Keyword(s):  
Hierarchical Models ◽  
Xylella Fastidiosa ◽  
Buffer Zone ◽  
Distribution Models ◽  
Stationary Model ◽  
Bayesian Hierarchical ◽  
Occurrence Data ◽  
Predicted Probability ◽  
Dispersal Barriers ◽  
Physical Barriers

Spatial species distribution models often assume isotropy and stationarity, implying that spatial dependence is direction invariant and uniform throughout the study area. However, these assumptions are violated when dispersal barriers are present. Despite this, the issue of non-stationarity has been little explored in the context of plant health. The objective of this study was to evaluate the influence of barriers in the distribution of Xylella fastidiosa in the demarcated area in Alicante, Spain. Occurrence data from 2018 were analyzed through spatial Bayesian hierarchical models. The stationary model, illustrating a scenario without control interventions or geographical features, was compared with three non-stationary models: a model with mountains as physical barriers, and two models with a continuous and discontinuous perimeter barrier representing hypothetical control interventions. In the stationary model the posterior mean of the spatial range, as the distance where two observations are uncorrelated, was 4,030 m 95% CI (2,907, 5,564). This distance can be used to define the buffer zone in the demarcated area. The predicted probability of X. fastidiosa presence in the area outside the barrier was 0.46 with the stationary model, whereas it was reduced to 0.29 and 0.36 with the continuous and discontinuous barrier models, respectively. Differences between the discontinuous and continuous barrier models showed that breaks, where no control interventions were implemented, resulted in a higher predicted probability of X. fastidiosa presence in the areas with low sampling intensity. These results may help authorities prioritize the areas for surveillance and disease control.

Xylella fastidiosa (Pierce's disease of grapevines).

2021 ◽  
Author(s):  
Rebekah Robinson
Keyword(s):  
Food Safety ◽  
Host Plants ◽  
Xylella Fastidiosa ◽  
Life Stage ◽  
Xylem Sap ◽  
European Food Safety Authority ◽  
Control Measures ◽  
Homalodisca Vitripennis ◽  
Plant Host ◽  
New Host

Abstract Xylella fastidiosa has a wide plant host range and spectrum of insect species capable of serving as vectors which should increase the bacterium's invasiveness and make it difficult to prevent introduction via live plants from the tropical or subtropical Americas. The spread of phony disease of peach within the south-eastern USA from the 1890s until about 1930 and of citrus variegated chlorosis disease of orange throughout Brazil in the 1990s indicates that new strains of X. fastidiosa have the potential to spread over a few years to cause increasing damage. Intersubspecific homologous recombination of strains is implicated in the potential for invasion of new host plants (Nunney et al., 2014). X. fastidiosa represents a very serious threat for the EPPO region. In 2013 the bacterium was reported causing serious damage to olive trees in Puglia, Italy. It was also detected in numerous other host plants (mainly ornamentals). Colonisation of a host with X. fastidiosa does not always equate to disease development and an endophytic life stage has been suggested (Chatterjee et al., 2008). These non-symptomatic hosts and hosts which are slow to develop symptoms can limit the effectiveness of quarantine procedures and may provide a reservoir for maintenance of the pathogen in the wider environment. According to the EFSA Panel on Plant Health (European Food Safety Authority, 2015), establishment and spread of X. fastidiosa in the EU is very likely. The consequences are considered to be major because yield losses and other damage would be high and require costly control measures. X. fastidiosa is included in the EPPO A1 list of pests recommended for regulation as quarantine pests. Among potential insect vectors, only Homalodisca vitripennis, Xyphon fulgida, Draeculacephala minerva and Graphocephala atropunctata are also listed in the EPPO A1 list. The European Food Safety Authority suggests that all xylem sap feeder insects should be regarded as potential vectors of X. fastidiosa. Elbeaino et al. (2014b) detected X. fastidiosa in the phloem feeder Euscelis lineolatus in Italy, suggesting that potential vectors may include phloem feeding insects. Further studies are needed to confirm transmission in E. lineolatus. Newly introduced isolates of X. fastidiosa are likely to be transmitted by endemic vector species even without the introduction of non-native vectors (Almeida et al., 2005).In summary, X. fastidiosa may have the potential to invade agro-ecosystems in Mediterranean regions wherever suitable vectors (overwintering in the adult stage and thus able to inoculate vines during spring) are endemic or become established. The same may be true for tropical-subtropical Asia and Africa.

scholarly journals Controlling the Spatial Spread of a Xylella Epidemic

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
Sebastian Aniţa ◽  
Vincenzo Capasso ◽  
Simone Scacchi
Keyword(s):  
Spatial Structure ◽  
Numerical Simulations ◽  
Control Strategies ◽  
Xylella Fastidiosa ◽  
Cost Effective ◽  
Olive Tree ◽  
Control Measures ◽  
Weed Biomass ◽  
Spatial Spread ◽  
Olive Trees

AbstractIn a recent paper by one of the authors and collaborators, motivated by the Olive Quick Decline Syndrome (OQDS) outbreak, which has been ongoing in Southern Italy since 2013, a simple epidemiological model describing this epidemic was presented. Beside the bacterium Xylella fastidiosa, the main players considered in the model are its insect vectors, Philaenus spumarius, and the host plants (olive trees and weeds) of the insects and of the bacterium. The model was based on a system of ordinary differential equations, the analysis of which provided interesting results about possible equilibria of the epidemic system and guidelines for its numerical simulations. Although the model presented there was mathematically rather simplified, its analysis has highlighted threshold parameters that could be the target of control strategies within an integrated pest management framework, not requiring the removal of the productive resource represented by the olive trees. Indeed, numerical simulations support the outcomes of the mathematical analysis, according to which the removal of a suitable amount of weed biomass (reservoir of Xylella fastidiosa) from olive orchards and surrounding areas resulted in the most efficient strategy to control the spread of the OQDS. In addition, as expected, the adoption of more resistant olive tree cultivars has been shown to be a good strategy, though less cost-effective, in controlling the pathogen. In this paper for a more realistic description and a clearer interpretation of the proposed control measures, a spatial structure of the epidemic system has been included, but, in order to keep mathematical technicalities to a minimum, only two players have been described in a dynamical way, trees and insects, while the weed biomass is taken to be a given quantity. The control measures have been introduced only on a subregion of the whole habitat, in order to contain costs of intervention. We show that such a practice can lead to the eradication of an epidemic outbreak. Numerical simulations confirm both the results of the previous paper and the theoretical results of the model with a spatial structure, though subject to regional control only.

scholarly journals Novel Virulent Bacteriophages Infecting Mediterranean Isolates of the Plant Pest Xylella fastidiosa and Xanthomonas albilineans

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 725
Author(s):  
Fernando Clavijo-Coppens ◽  
Nicolas Ginet ◽  
Sophie Cesbron ◽  
Martial Briand ◽  
Marie-Agnès Jacques ◽  
...  
Keyword(s):  
Phage Therapy ◽  
Xylella Fastidiosa ◽  
Infected Plant ◽  
Mediterranean Area ◽  
Genomic Features ◽  
Phylogeny Analysis ◽  
Plant Pest ◽  
European Regulations ◽  
Surrogate Host

Xylella fastidiosa (Xf) is a plant pathogen causing significant losses in agriculture worldwide. Originating from America, this bacterium caused recent epidemics in southern Europe and is thus considered an emerging pathogen. As the European regulations do not authorize antibiotic treatment in plants, alternative treatments are urgently needed to control the spread of the pathogen and eventually to cure infected crops. One such alternative is the use of phage therapy, developed more than 100 years ago to cure human dysentery and nowadays adapted to agriculture. The first step towards phage therapy is the isolation of the appropriate bacteriophages. With this goal, we searched for phages able to infect Xf strains that are endemic in the Mediterranean area. However, as Xf is truly a fastidious organism, we chose the phylogenetically closest and relatively fast-growing organism X. albineans as a surrogate host for the isolation step. Our results showed the isolation from various sources and preliminary characterization of several phages active on different Xf strains, namely, from the fastidiosa (Xff), multiplex (Xfm), and pauca (Xfp) subspecies, as well as on X. albilineans. We sequenced their genomes, described their genomic features, and provided a phylogeny analysis that allowed us to propose new taxonomic elements. Among the 14 genomes sequenced, we could identify two new phage species, belonging to two new genera of the Caudoviricetes order, namely, Usmevirus (Podoviridae family) and Subavirus (Siphoviridae family). Interestingly, no specific phages could be isolated from infected plant samples, whereas one was isolated from vector insects captured in a contaminated area, and several from surface and sewage waters from the Marseille area.

Puccinia tulipae. [Descriptions of Fungi and Bacteria].

2001 ◽  
Author(s):  
Yu. Ya. Tykhonenko
Keyword(s):  
Geographical Distribution ◽  
Host Plants ◽  
Infected Plant

Abstract A description is provided for Puccinia tulipae. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. DISEASE: Rust of Tulipa species only. HOSTS: Tulipa alberti, T. biflora, T. graniticola, T. ingens, T. kolpakovskiana, T. lanata, T. micheliana, T. ostrovskiana, T. praestans, T. schrenkii (Liliaceae). GEOGRAPHICAL DISTRIBUTION: ASIA: Afghanistan, Kazakhstan, Turkmenistan, Uzbekistan. EUROPE: Austria, Bulgaria, Germany, Italy, Russia (Astrakhan, Rostov), Ukraine. TRANSMISSION: No detailed studies have been reported; teliospores are presumably dispersed by air currents and then germinate to produce basidia with basidiospores, which re-infect the host plants; the fungus might also survive in bulbs of the infected plant.

THE DISTRIBUTION AND ABUNDANCE OF ADULT GRASSHOPPERS (ACRIDIDAE) IN CROPS IN ALBERTA, 1918–1975

1977 ◽  
Vol 109 (4) ◽  
pp. 575-592 ◽  
Author(s):  
D. S. Smith ◽  
N. D. Holmes
Keyword(s):  
Control Measures ◽  
Melanoplus Sanguinipes ◽  
Infested Area

AbstractAnnual surveys of the adults show that outbreaks of grasshoppers in cultivated crops in Alberta have occurred in 32 of 58 years. Five outbreaks have occurred, lasting from 3 to 14 years, interspersed by periods of low infestation lasting from 3 to 9 years. Some control measures, however, were required every year even during periods of low infestation. The highest recorded adult populations occurred in 1933, 1936, and 1962, and the lowest in 1952 and 1969.During most periods with low populations, infestation were confined mainly to the area south of the Bow and South Saskatchewan rivers. When high populations occurred, the infested areas increased in size and extended north to the Battle River. The largest infested area covered 48,600 sq. miles and the smallest was 300 sq. miles.Two species of grasshoppers, Camnula pellucida (Scudder) and Melanoplus sanguinipes (Fabr.), generally predominated in separate regions. Melanoplus bivittatus (Say) predominated only during periods of low grasshopper infestation. Melanoplus packardii Scudder was restricted in its range and became noticeable when the grasshopper outbreaks were declining.

scholarly journals A new variant of Xylella fastidiosa subspecies multiplex detected in different host plants in the recently emerged outbreak in the region of Tuscany, Italy

2019 ◽  
Vol 154 (4) ◽  
pp. 1195-1200 ◽  
Author(s):  
Maria Saponari ◽  
Giusy D’Attoma ◽  
Raied Abou Kubaa ◽  
Giuliana Loconsole ◽  
Giuseppe Altamura ◽  
...  
Keyword(s):  
Host Plants ◽  
Xylella Fastidiosa ◽  
New Variant

ADDITIONAL HOST PLANTS OF CLOVER PHYLLODY IN CANADA

1974 ◽  
Vol 54 (4) ◽  
pp. 755-763 ◽  
Author(s):  
L. N. CHIYKOWSKI
Keyword(s):  
Plant Species ◽  
Host Plants ◽  
Infected Plant ◽  
Symptom Development ◽  
Source Plant ◽  
Aster Leafhopper ◽  
Clover Phyllody

Symptoms were observed on 35 out of 74 plant species, in 15 families inoculated with clover phyllody by the aster leafhopper (Macrosteles fascifrons (Stal)). Symptomatology for some of the hosts is described and illustrated. There were differences in numbers of plants infected, length of time for symptom development, and numbers of insects surviving on the various species of plants, but these were not correlated. Although the clover phyllody agent was transmitted to asters from 17 of 19 infected plant species the number of leafhoppers that became inoculative varied considerably depending on the source plant species.

scholarly journals Ectopic Expression of Xylella fastidiosa rpfF Conferring Production of Diffusible Signal Factor in Transgenic Tobacco and Citrus Alters Pathogen Behavior and Reduces Disease Severity

2017 ◽  
Vol 30 (11) ◽  
pp. 866-875 ◽  
Author(s):  
R. Caserta ◽  
R. R. Souza-Neto ◽  
M. A. Takita ◽  
S. E. Lindow ◽  
A. A. De Souza
Keyword(s):  
Transgenic Tobacco ◽  
Disease Severity ◽  
Host Plants ◽  
Xylella Fastidiosa ◽  
Ectopic Expression ◽  
Signal Molecules ◽  
Insect Vector ◽  
Expression Of Genes ◽  
Diffusible Signal Factor ◽  
Population Sizes

The pathogenicity of Xylella fastidiosa is associated with its ability to colonize the xylem of host plants. Expression of genes contributing to xylem colonization are suppressed, while those necessary for insect vector acquisition are increased with increasing concentrations of diffusible signal factor (DSF), whose production is dependent on RpfF. We previously demonstrated that transgenic citrus plants ectopically expressing rpfF from a citrus strain of X. fastidiosa subsp. pauca exhibited less susceptibility to Xanthomonas citri subsp. citri, another pathogen whose virulence is modulated by DSF accumulation. Here, we demonstrate that ectopic expression of rpfF in both transgenic tobacco and sweet orange also confers a reduction in disease severity incited by X. fastidiosa and reduces its colonization of those plants. Decreased disease severity in the transgenic plants was generally associated with increased expression of genes conferring adhesiveness to the pathogen and decreased expression of genes necessary for active motility, accounting for the reduced population sizes achieved in the plants, apparently by limiting pathogen dispersal through the plant. Plant-derived DSF signal molecules in a host plant can, therefore, be exploited to interfere with more than one pathogen whose virulence is controlled by DSF signaling.

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