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 Evaluation of Therapeutic Treatments to Manage Oak Bacterial Leaf Scorch

2010 ◽  
Vol 36 (3) ◽  
pp. 140-146
Author(s):  
John Hartman ◽  
Ed Dixon ◽  
Shawn Bernick
Keyword(s):  
Disease Management ◽  
Growth Regulator ◽  
Late Summer ◽  
Golf Course ◽  
Tree Disease ◽  
Leaf Scorch ◽  
Street Tree ◽  
Quercus Palustris ◽  
Horse Farm ◽  
Bacterial Leaf Scorch

Bacterial leaf scorch is a very serious tree disease, especially for oaks in Kentucky, U.S. landscapes. From 2003 to 2007, several potentially therapeutic disease management treatments were tried on diseased pin oaks (Quercus palustris) growing in golf course, street tree, and horse farm environments. Treatments included root flare soil drenches of paclobutrazol, adjuvant-assisted basal trunk applications of anti-microbial compounds, and springtime root flare injections of oxytetracycline. Paclobutrazol drenches caused expected growth regulator effects but did not consistently reduce bacterial leaf scorch of golf course and street trees. Antibiotics applied directly to trunks of infected trees with an adjuvant had no effect on levels of bacterial leaf scorch. Compared to untreated trees, springtime root flare injections of oxytetracycline reduced scorch levels and delayed by about two weeks, the time of appearance of late summer scorch symptoms. Injections done three weeks after full expansion of first leaves provided better results than injections done earlier or later in the spring. Therapeutic treatments do not provide a cure for trees infected with bacterial leaf scorch, but may prolong tree life.

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 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, 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 Transmission of Xylella fastidiosa through Pecan Rootstock

HortScience ◽  
2006 ◽  
Vol 41 (6) ◽  
pp. 1455-1456 ◽  
Author(s):  
R. S. Sanderlin ◽  
R. A. Melanson
Keyword(s):  
Xylella Fastidiosa ◽  
Early Spring ◽  
Carya Illinoinensis ◽  
In Vitro Cultures ◽  
High Rate ◽  
Significant Source ◽  
Symptom Development ◽  
Leaf Scorch ◽  
Bacterial Leaf Scorch

Xylella fastidiosa Wells et al., the pathogen that causes pecan [Carya illinoinensis (Wangenh.) C. Koch] bacterial leaf scorch disease, was demonstrated to be highly transmissible through graft unions from infected rootstock into new growth developing from scions. Infected rootstocks were obtained by inoculation of pecan seedlings in pots with in vitro cultures of the pathogen. If rootstock infection occurs in nature, transmission of the pathogen into tissue growing from scions could serve as a significant source of introduction of the disease into pecan orchards. Because symptom development in infected trees typically begins in midsummer and grafting takes place in the early spring, it would be difficult to identify infected rootstock before grafting. Commercial pecan growers sometimes attempt to eliminate bacterial leaf scorch from trees by regrafting to other cultivars. The high rate of transmission from infected rootstocks observed in this test and the lack of knowledge of cultivars with resistance to the disease makes this practice ineffective.

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 Reduction of Xylella fastidiosa Transmission Through Pecan Scion Wood by Hot-Water Treatment

Plant Disease ◽  
2008 ◽  
Vol 92 (7) ◽  
pp. 1124-1126 ◽  
Author(s):  
R. S. Sanderlin ◽  
R. A. Melanson
Keyword(s):  
Water Treatment ◽  
Xylella Fastidiosa ◽  
Carya Illinoinensis ◽  
Hot Water ◽  
Hot Water Treatment ◽  
Leaf Scorch ◽  
Cape Fear ◽  
Graft Success ◽  
Water Treatments ◽  
Bacterial Leaf Scorch

Pecan (Carya illinoinensis) bacterial leaf scorch disease, caused by the bacterium Xylella fastidiosa, causes leaf loss and reduction in yield of pecans. One of the ways that the pathogen infects newly developing trees is by graft-transmission through infected scion wood. Submersion of pecan scion wood in 46°C water for 30 min greatly reduced transmission of X. fastidiosa following grafting. During a 2-year study with potted rootstock grafted to either hot-water-treated or nontreated scion wood collected from limbs of ‘Cape Fear’ pecan infected with X. fastidiosa, the pathogen was detected in 21% of the trees that developed from the nontreated scion wood and 0.7% of the trees from the hot-water-treated scions. The hot-water treatment of 46°C for 30 min did not affect graft success. Likewise, scion diameter had no effect on success of grafting or on the efficacy of hot-water treatment. Similar hot-water treatments have been efficacious in elimination of X. fastidiosa and some other pathogens from grapevine cuttings. The use of the hot-water treatment demonstrated in this report could be helpful to individual pecan growers and nurseries that use scion wood that may be infected with X. fastidiosa to reduce the occurrence of pecan bacterial leaf scorch disease in new trees.

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