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 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 Cultivar and Seedling Susceptibility to Pecan Bacterial Leaf Scorch Caused by Xylella fastidiosa and Graft Transmission of the Pathogen

Plant Disease ◽  
2005 ◽  
Vol 89 (5) ◽  
pp. 446-449 ◽  
Author(s):  
R. S. Sanderlin
Keyword(s):  
Xylella Fastidiosa ◽  
Carya Illinoinensis ◽  
Disease Development ◽  
Needle Puncture ◽  
Symptom Development ◽  
Leaf Scorch ◽  
Severity Of Disease ◽  
Graft Transmission ◽  
Bacterial Leaf Scorch

The xylem-limited bacterium Xylella fastidiosa was detected in 20 cultivars and 4 seedling trees with pecan bacterial leaf scorch (PBLS) symptoms during a 2-year survey of commercial pecan (Carya illinoinensis) cultivars. The orchard survey and inoculation trials indicated that several of the currently recommended cultivars, as well as older, popular cultivars, are susceptible to infection by the bacterium and develop PBLS. The severity of disease development was variable between cultivars and within cultivars. Eight of 9 cultivars growing in pots that were needle-puncture inoculated with X. fastidiosa became infected and developed the disease. Currently, no cultivars have been identified that are not susceptible to infection and symptom development. All 6 seedling types that were inoculated became infected and developed PBLS. The frequency of infection of the seedlings was greater than the cultivars; 88% of the inoculated seedlings and 44% of the inoculated cultivar trees were infected. It was demonstrated that the pathogen could be transmitted through scion wood. Because pecan cultivars are clonally propagated, graft-transmission may represent a major source of pecan infection.

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 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.

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 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 First Report of Koch's Postulates Completion of Sudden Death Syndrome of Soybean in Argentina

Plant Disease ◽  
2003 ◽  
Vol 87 (4) ◽  
pp. 447-447 ◽  
Author(s):  
M. Scandiani ◽  
D. Ruberti ◽  
R. Pioli ◽  
A. Luque ◽  
L. Giorda
Keyword(s):  
Sudden Death ◽  
Fusarium Solani ◽  
Colony Growth ◽  
Positive Control ◽  
Sudden Death Syndrome ◽  
Symptom Development ◽  
Koch’S Postulates ◽  
Interveinal Chlorosis ◽  
Soil Infestation ◽  
Koch's Postulates

Foliage symptoms on soybean resembling those of sudden death syndrome were detected in Argentina during 1991 and 1992 in the Pampas Region and during 1992 and 1993 in the Northwest Region. Isolations were made in 1999, 2000, and 2001 from soybean plants (Glycine max (L.) Merr.) showing these symptoms. Five isolates of fungi obtained from taproot tissue and blue sporulation on taproot exteriors were selected for further evaluation. These isolates were plated on potato dextrose agar supplemented with streptomycin (PDAS). Based on the spore morphology, colony growth rate, morphology and pigmentation on PDAS, and lack of microconidia (1) five isolates were identified as Fusarium solani f. sp. glycines. Soybean cvs. Ripley, Spencer, Pioneer 9492RR, and A6445 RG were inoculated in greenhouse tests with each of the isolates using toothpick and soil infestation methods for a total of six experiments. Isolate 171 provided by J. Rupe (University of Arkansas, Fayetteville) was tested as a positive control. Foliar symptoms typical of sudden death syndrome and similar to those in the field were observed 14 and 25 days, respectively, after inoculations using the toothpick and soil infestation methods. Lesions produced on leaves averaged 3.6 for all five isolates and 4 for the reference strain using a disease severity scale where: 1 = no symptoms; 2 = slight symptom development with mottling and mosaic on leaves (1 to 20% foliage affected); 3 = moderate symptom development with interveinal chlorosis and necrosis on foliage (21 to 50% foliage affected); 4 = heavy symptom development with interveinal chlorosis and necrosis (51 to 80% foliage affected); and 5 = severe interveinal chlorosis and necrosis (81 to 100% foliage affected). Noninoculated controls were symptomless. Differences in virulence were observed among the isolates. Based on disease symptoms in the greenhouse and cultural morphology on PDAS, the isolates were classified as Fusarium solani f. sp. glycines. Isolates recovered from symptomatic plants resembled Fusarium solani f. sp. glycines on PDAS and peptone/p-chloro-nitrobenzene agar amended with streptomycin, confirming Koch's postulates. Fusarium solani f. sp. glycines was recovered from 60% of inoculated plants. Reference: (1) K. W. Roy et al. Plant Dis. 81:1100,1997.

scholarly journals Evidence That Xylella fastidiosa Is Associated with Pecan Fungal Leaf Scorch

Plant Disease ◽  
1998 ◽  
Vol 82 (2) ◽  
pp. 264-264 ◽  
Author(s):  
R. S. Sanderlin
Keyword(s):  
Recent Work ◽  
Positive Reaction ◽  
Xylella Fastidiosa ◽  
Carya Illinoinensis ◽  
Enzyme Linked Immunosorbent Assay ◽  
Leaf Scorch ◽  
The Past ◽  
Exact Etiology ◽  
Consistent Feature ◽  
Cape Fear

Several different leaf scorch symptomatologies occur on the foliage of pecan (Carya illinoinensis). The causes of these different scorch symptoms have been associated with environmental stresses, nutritional imbalances, mites, and pathogens. One type of leaf scorch is characterized by necrosis beginning at the tips or margins of the leaflets and progressing toward the midrib and base of the leaflets. The most distinguishing feature of this type of leaf scorch is a dark brown, black, or purplish band of tissue at the interface of the necrotic and green leaflet tissue. This band does not occur on all affected leaflets, but is a consistent feature with this symptomatology. Leaflets with this leaf scorch usually abscise before the entire leaflet becomes necrotic. Affected leaflets will abscise from a compound leaf, while leaflets without symptoms remain on the rachis. When this scorch is severe, the entire leaf including the rachis may abscise. The symptoms are often confined to one area of the tree. Symptoms of this disease appear as early as June but often begin in July. Incidence and severity increase through the remainder of summer and into fall. Over the past 25 years, several different genera of fungi have been reported as being associated with this leaf scorch (2). The phenomenon was named fungal leaf scorch (FLS) because of the association with fungi and the observation that some fungicides reduced the severity of leaf scorch. Genera of fungi implicated in the development of FLS were Pestalotia, Epicoccum, Curvularia, and Fusarium. Recent work has indicated that the disease could be caused by a Phomopsis sp. or Glomerella cingulata or both (1). The symptoms and epidemiology of the FLS are similar to other leaf scorch diseases of hardwood caused by the fastidious xylem-limited bacterium Xylella fastidiosa. A commercial enzyme-linked immunosorbent assay (Agdia, Elkhart, IN) was used to screen for this organism in association with FLS. Assays were conducted by extracting from a composite sample of 9 to 12 sections (approximately 3 cm long) taken from 3 to 4 rachises of each tree tested. Positive reaction for the presence of X. fastidiosa in rachises was recorded from 10 of 10 trees with symptoms of FLS on the Cape Fear cultivar. One of two trees was positive from Cape Fear leaves without symptoms. Symptomless foliage from two less susceptible cultivars, Stuart (two trees) and Sumner (one tree), assayed negative for the bacterium. The association of X. fastidiosa with symptoms of FLS provides evidence that this organism is involved in the etiology of pecan leaf scorch; however, further work is needed to determine the exact etiology. References: (1). A. J. Latham et al. Plant Dis. 79:182, 1995. (2) R. H. Littrell and R. E. Worley. Phytopathology 62:805, 1972.

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