scholarly journals Distribution of Xylella fastidiosa in Blueberry Stem and Root Sections in Relation to Disease Severity in the Field

Plant Disease ◽  
2014 ◽  
Vol 98 (4) ◽  
pp. 443-447 ◽  
Author(s):  
R. M. Holland ◽  
R. S. C. Christiano ◽  
E. Gamliel-Atinsky ◽  
H. Scherm
Keyword(s):  
Disease Severity ◽  
Cultural Practices ◽  
Xylella Fastidiosa ◽  
Severe Disease ◽  
Management Strategies ◽  
Leaf Scorch ◽  
High Disease Severity ◽  
Southern Highbush ◽  
Species Specific ◽  
Bacterial Leaf Scorch

Xylella fastidiosa causes bacterial leaf scorch, a new disease of southern highbush blueberry in the southeastern United States. Infections occlude the xylem of affected plants, causing drought-like symptoms and, eventually, plant death. To assess the likelihood of mitigation of bacterial leaf scorch through cultural practices such as pruning or hedging of affected plants, we determined the localization and population density of X. fastidiosa in naturally infected blueberry plants with varying levels of bacterial leaf scorch severity. Stem segments were sampled from the current season's growth down to the base of the plant, as were root segments on plants that were either asymptomatic or had light, moderate, or severe symptoms in three plantings affected by the disease. Stem sap was extracted from each segment and population densities of X. fastidiosa were determined using real-time polymerase chain reaction with species-specific primers. Detection frequencies were lowest (but non-zero) in sap from asymptomatic plants and highest in plants with severe symptoms. In asymptomatic plants, detection was generally least frequent (0 to 20.0%) in top and root sections and highest (4.6 to 55.6%) in middle and base stem sections. As disease severity increased, detection frequencies in roots increased to >80% in two plantings and to 60% in the third planting. Overall, detection frequencies were highest (>80%) in middle and base stem sections of plants from the moderate and severe disease classes. The lowest bacterial titers (averaging 0 to 2.1 × 101 CFU per 50 μl of sap) were observed in top and root sections of asymptomatic plants, whereas the highest titers (generally between 104 and 105 CFU per 50 μl of sap) were obtained from middle, base, and root sections of plants from the moderate and severe classes. The presence of the bacterium in middle and base stem sections at low disease severity indicates rapid distribution of X. fastidiosa in affected plants. Because the pathogen accumulates in the roots at moderate and high disease severity levels, management strategies such as pruning and mowing are unlikely to be effective in curing affected plants from bacterial leaf scorch.

Pecan Bacterial Leaf Scorch, Caused by Xylella fastidiosa, Is Endemic in Georgia Pecan Orchards

2018 ◽  
Vol 19 (4) ◽  
pp. 284-287 ◽  
Author(s):  
Clive H. Bock ◽  
Jonathan E. Oliver ◽  
Chunxian Chen ◽  
Michael H. Hotchkiss ◽  
Katherine L. Stevenson ◽  
...  
Keyword(s):  
Yield Loss ◽  
Xylella Fastidiosa ◽  
Severe Disease ◽  
The United States ◽  
Susceptible Cultivar ◽  
Leaf Scorch ◽  
Central Production ◽  
Cape Fear ◽  
Production Areas ◽  
Bacterial Leaf Scorch

Pecan bacterial leaf scorch (PBLS), caused by Xylella fastidiosa, can cause severe disease in some pecan cultivars, resulting in yield loss. Only recently has some information been obtained regarding the distribution and extent of the disease in pecan in any state in the United States. With emphasis on a susceptible cultivar, Cape Fear, we sampled a total of 91 trees in eight orchards from the southwestern and central production areas in Georgia (GA) and found 60.4% of trees sampled infected, most showing symptoms of PBLS. Further multilocus sequence typing from 16 of these trees confirmed presence X. fastidiosa. The results confirm that X. fastidiosa is widespread geographically in GA, and different cultivars may be infected. This is the first definitive report confirming X. fastidiosa causing PBLS in different pecan producing areas and cultivars in GA.

scholarly journals First Report of Bacterial Leaf Scorch Caused by Xylella fastidiosa on Southern Highbush Blueberry in Florida

Plant Disease ◽  
2009 ◽  
Vol 93 (11) ◽  
pp. 1220-1220 ◽  
Author(s):  
P. F. Harmon ◽  
D. L. Hopkins
Keyword(s):  
Xylella Fastidiosa ◽  
Vaccinium Corymbosum ◽  
Pathogen Transmission ◽  
Highbush Blueberry ◽  
Disease Symptoms ◽  
Leaf Scorch ◽  
Three Samples ◽  
Southern Highbush ◽  
Das Elisa ◽  
Bacterial Leaf Scorch

In May of 2008, samples of southern highbush blueberry (interspecific Vaccinium corymbosum hybrids) exhibiting marginal leaf necrosis were collected at a farm in Interlachen, FL. The cv. Star showed severe leaf scorch, partial defoliation, and a generally unthrifty growth structure of many thin twigs as has been observed in Georgia (1). The block of Star plants was approximately 10 years old and incidence of the disease was 100%. The grower reported the planting had become increasingly unproductive in the most recent 4 to 5 years. Plants of the cv. Windsor also showed scorch symptoms and yellow-to-red discoloration of leaves. Proportionally fewer Windsor plants showed disease symptoms than Star plants and the disease was not as severe on this cultivar on the basis of visual estimates at the time. Each sample consisted of 5 to 10 cuttings of spring wood with attached leaves showing marginal necrosis taken from a single plant. Three samples, two from Star plants and one from a Windsor plant, were divided into two subsamples each. One subsample was submitted to Agdia for Xylella fastidiosa double-antibody sandwich (DAS)-ELISA assay (TSE XF; Agdia Inc., Elkhart IN). All three samples were reported as positive for X. fastidiosa by DAS-ELISA. A number of asymptomatic plants from this farm and other additional farms were tested in the same manner and results were negative. The other subsample was used for isolation of the causal bacterium. Petioles and main veins from symptomatic leaves were surface disinfested in 1% sodium hypochlorite, cut into segments (0.5 cm), and squeezed with forceps or pliers. Sap that exuded from the segment was blotted directly onto periwinkle wilt medium (2). Bacterial colonies consistent in morphology with X. fastidiosa that were DAS-ELISA positive were obtained from all three samples. One isolate from each sample was inoculated into four Star plants each with the pin-pricking method (3). Leaf scorch symptoms were first observed 8 weeks after inoculation. By 12 weeks after inoculation, all plants inoculated with the three isolates had developed symptoms, including defoliation. Plants inoculated without bacteria showed no symptoms. X. fastidiosa was reisolated from symptomatic plants. Bacterial leaf scorch is an important emerging disease that threatens the southern highbush blueberry industry in the south. On certain cultivars like Star, the potential to reduce yield appears to be great. Differences between cultivars are likely, but have not yet been explored. Additional research is needed into the epidemiology of the disease and potential vectors of pathogen transmission. References: (1) C. Chang et al. HortScience 44:413, 2009. (2) M. Davis et al. Curr. Microbiol. 6:309, 1981. (3) D. L. Hopkins et al. Phytopathology 75:713, 1985.

scholarly journals Bacterial Leaf Scorch in the District of Columbia: Distribution, Host Range, and Presence of Xylella fastidiosa Among Urban Trees

Plant Disease ◽  
2014 ◽  
Vol 98 (12) ◽  
pp. 1611-1618 ◽  
Author(s):  
Jordan L. Harris ◽  
Patrick L. Di Bello ◽  
Monica Lear ◽  
Yilmaz Balci
Keyword(s):  
Tree Species ◽  
Xylella Fastidiosa ◽  
Management Strategies ◽  
District Of Columbia ◽  
Urban Environments ◽  
Urban Trees ◽  
Enzyme Linked Immunosorbent Assay ◽  
Leaf Scorch ◽  
Crown Dieback ◽  
Bacterial Leaf Scorch

A survey of urban trees affected by bacterial leaf scorch (BLS) caused by Xylella fastidiosa was conducted in the District of Columbia during 2011 and 2012. Over 20 species of urban trees were evaluated at 95 sites. Symptomatic and asymptomatic foliage from trees with BLS symptoms and foliage from neighboring asymptomatic trees were sampled. An X. fastidiosa-specific enzyme-linked immunosorbent assay (ELISA) and a polymerase chain reaction assay were used to detect and identify the strains from environmental samples. Symptomatic trees testing ELISA-positive for X. fastidiosa occurred most frequently with Quercus palustris, Q. rubra, Ulmus americana, and Platanus occidentalis. The bacterium was also less frequently identified on eight other symptomatic and five asymptomatic tree species. On infected trees, the bacterium was also detected on the asymptomatic portion of seven tree species. All strains were identified as the X. fastidiosa subsp. multiplex genotype ALSII except on Morus alba, where the genotype ALSI and the subsp. sandyi were detected. The occurrence of crown dieback was found significantly associated with X. fastidiosa-infection on Q. palustris, Q. rubra, U. americana, and P. occidentalis. Because this pathogen continues to perpetuate uncontrolled in urban environments, there is a pressing need to identify long-term management strategies that abate disease.

scholarly journals Evidence that Xylella fastidiosa Can Cause Leaf Scorch Disease of Pecan

Plant Disease ◽  
2000 ◽  
Vol 84 (12) ◽  
pp. 1282-1286 ◽  
Author(s):  
R. S. Sanderlin ◽  
K. I. Heyderich-Alger
Keyword(s):  
Xylella Fastidiosa ◽  
Carya Illinoinensis ◽  
Symptom Development ◽  
Koch’S Postulates ◽  
Leaf Scorch ◽  
Symptomatic Tissue ◽  
Koch's Postulates ◽  
Bacterial Leaf Scorch

The disease known as pecan fungal leaf scorch has been reported to be either caused by or associated with several fungi since it was first recognized in 1972. Data are presented that indicate the disease is initiated by the fastidious xylem-limited bacterium Xylella fastidiosa. X. fastidiosa was found consistently associated with fungal leaf scorch disease of pecan (Carya illinoinensis) in commercial orchards in Louisiana. It was generally not detected in symptomless trees. The disease was reproduced by inoculation of greenhouse seedlings and grafted trees with cultures of the bacterium obtained from leaves with fungal leaf scorch. The bacterium was reisolated from symptomatic tissue of inoculated pecan seedlings, but not from symptomless plants inoculated with water to complete Koch's postulates. It is proposed that the name of the disease be changed to pecan bacterial leaf scorch because fungi do not appear to be necessary for symptom development.

scholarly journals First Report of Pecan Bacterial Leaf Scorch Caused by Xylella fastidiosa in Pecan (Carya illinoinensis) in Arizona, New Mexico, California, and Texas

Plant Disease ◽  
2017 ◽  
Vol 101 (11) ◽  
pp. 1949-1949 ◽  
Author(s):  
A. E. Hilton ◽  
Y-.K. Jo ◽  
K. Cervantes ◽  
R. A. Stamler ◽  
J. J. Randall ◽  
...  
Keyword(s):  
New Mexico ◽  
Xylella Fastidiosa ◽  
Carya Illinoinensis ◽  
First Report ◽  
Leaf Scorch ◽  
Bacterial Leaf Scorch

scholarly journals Bacterial Leaf Scorch of Landscape Trees: What We Know and What We Do Not Know

2007 ◽  
Vol 33 (6) ◽  
pp. 376-385
Author(s):  
James Sherald
Keyword(s):  
Disease Management ◽  
Urban Forest ◽  
Xylella Fastidiosa ◽  
Diagnostic Techniques ◽  
Individual Tree ◽  
Leaf Scorch ◽  
Property Owners ◽  
Symptom Awareness ◽  
Landscape Trees ◽  
Bacterial Leaf Scorch

Xylella fastidiosa has been recognized as a pathogen of landscape trees for over 25 years. Collectively, these diseases are referred to as bacterial leaf scorch (BLS). Arborists, property owners, and communities are now beginning to recognize BLS as a serious threat to the urban forest. Although advances in symptom awareness and diagnostic techniques have enabled arborists to diagnose BLS, there are many questions regarding host range, transmission, pathogeneses, disease management, and individual tree therapy that remain unanswered.

scholarly journals Bacterial Leaf Scorch, a New Blueberry Disease Caused by Xylella fastidiosa

HortScience ◽  
2009 ◽  
Vol 44 (2) ◽  
pp. 413-417 ◽  
Author(s):  
Chung-Jan Chang ◽  
Ruth Donaldson ◽  
Phil Brannen ◽  
Gerard Krewer ◽  
Robert Boland
Keyword(s):  
Tissue Sample ◽  
Xylella Fastidiosa ◽  
Root Tissue ◽  
Enzyme Linked Immunosorbent Assay ◽  
Initial Symptom ◽  
Tissue Samples ◽  
Leaf Scorch ◽  
Elisa Testing ◽  
Southern Belle ◽  
Bacterial Leaf Scorch

Since 2004, growers and scientists have observed a disorder described as “yellow twig” or “yellow stem” affecting a major selection of southern highbush blueberry, FL 86-19, in the south Georgia blueberry production region. The initial symptom observed was leaf marginal chlorosis and subsequent necrosis, which eventually progressed throughout the whole leaf resulting in early leaf fall. Thin, yellow twigs or yellow stems became evident on some cultivars. The described symptoms on blueberry were similar to those exhibited on grapes with Pierce's disease and on plum with leaf scald disease. This prompted the enzyme-linked immunosorbent assay (ELISA) tests and isolations of Xylella fastidiosa, which is the causal agent of the previously mentioned grape and plum diseases. Two leaf and two root tissue samples were collected from a diseased FL 86-19 plant for isolation and ELISA testing on 2 Mar. 2006. ELISA results indicated all four tissues tested positive for the bacterial pathogen, X. fastidiosa, whereas only the two root tissues provided positive isolations. One leaf and one root tissue sample were later collected from each of five additional diseased plants for isolation and ELISA testing. Both isolation and ELISA testing methods obtained positive results. Cultures were multiplied to inoculate seedlings of three cultivars: ‘Southern Belle’ (eight plants), ‘Premier’ (six), and ‘Powderblue’ (six) on 23 May 2006 and one selection, FL 86-19 (eight), on 31 May 2006. Two FL 86-19 plants started to show symptoms of marginal necrosis 54 days postinoculation, whereas one plant each of ‘Southern Belle’ and ‘Powderblue’ started to show symptoms of marginal necrosis 63 days postinoculation and ‘Premier’ stayed symptomless. All eight culture-inoculated FL 86-19 plants (100%) showed symptoms 72 days postinoculation, but no symptoms were observed on the control plants. One hundred twenty-six days postinoculation, two ‘Powderblue’ and four ‘Southern Belle’ plants showed mild symptoms, whereas all ‘Premier’ plants were asymptomatic. Positive reisolations of the bacteria from the inoculated symptomatic plants, not from asymptomatic plants, fulfilled Koch's postulates, which confirmed X. fastidiosa was the causal bacterium of the new blueberry disorder, the bacterial leaf scorch of blueberry.

scholarly journals Impacts of Vaccinium arboreum Rootstocks on Vegetative Growth and Yield in Two Southern Highbush Blueberry Cultivars

HortScience ◽  
2020 ◽  
Vol 55 (1) ◽  
pp. 40-45
Author(s):  
Rebecca L. Darnell ◽  
Jeffrey G. Williamson ◽  
Deanna C. Bayo ◽  
Philip F. Harmon
Keyword(s):  
Pine Bark ◽  
Soluble Solids ◽  
Growth And Yield ◽  
Soil Conditions ◽  
Highbush Blueberry ◽  
Leaf Scorch ◽  
Canopy Volume ◽  
Southern Highbush ◽  
Vaccinium Arboreum ◽  
Bacterial Leaf Scorch

Vaccinium arboreum Marsh is a small tree adapted to low-organic matter soils and is one of the few ericaceous species that tolerates soil pH greater than 6.0. It has a deep root system and is more drought tolerant than cultivated blueberry. The use of V. arboreum as a rootstock for commercial blueberry production has been studied previously in young blueberry plantings. The objective of the current study was to expand on earlier work and evaluate growth, productivity, and tolerance to bacterial leaf scorch (Xylella fastidiosa) in established plantings of own-rooted vs. grafted southern highbush blueberry (SHB). Two field plantings of grafted and own-rooted ‘Meadowlark’ and ‘Farthing’ SHB were established in May 2011: one at the University of Florida–Institute of Food and Agricultural Sciences (UF-IFAS) Plant Science Research and Education Unit in Citra, FL, and the other at a commercial blueberry farm in Archer, FL. At both sites, four rootstock–scion combinations were grown in either pine bark-amended or nonamended soil. Canopy volume was greater in grafted compared with own-rooted ‘Meadowlark’ at both locations throughout the 4 years of the study (2015–18), whereas canopy volume in ‘Farthing’ was not consistently different. For both cultivars and both locations, canopy volume was greater on amended compared with nonamended soil. Although canopy growth was not consistently increased in the grafted compared with own-rooted plants, yield was greater in grafted plants of both cultivars at both locations. Cumulative yield over the 4 years was similar between grafted plants grown on both amended and nonamended soil, and was significantly greater than yield of own-rooted plants on nonamended soil, suggesting the use of this rootstock may decrease the requirement for pine bark amendment. In general, grafted plants produced larger berries, with no negative impacts on fruit soluble solids, titratable acidity, or firmness. ‘Meadowlark’—an SHB cultivar that exhibits high sensitivity to bacterial leaf scorch—displayed decreased development of bacterial leaf scorch symptoms when grafted onto V. arboreum compared with own-rooted plants. These results indicate the potential benefits of grafting SHB onto V. arboreum rootstock, particularly under marginal soil conditions. However, a complete economic analysis that also takes into account any differences in longevity between the two systems must be done to determine whether the benefits of using grafting are feasible financially for the grower.

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