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First Report of Laurel Wilt Disease Caused by a Raffaelea sp. on Avocado in Florida

Authors:
A.E. III Mayfield
A.E. III Mayfield
A.E. III Mayfield
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Jason Andrew Smith at University of Mount Union
Jason Andrew Smith
Marc A. Hughes at US Forest Service
Marc A. Hughes
Tyler Dreaden at University of Florida
Tyler Dreaden
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Abstract

Laurel wilt is a vascular disease of redbay (Persea borbonia (L.) Spreng.) and other plants in the family Lauraceae in the southeastern United States. It is caused by a fungus (Raffaelea sp.) that is vectored by a non-native insect of Asian origin, the redbay ambrosia beetle (Xyleborus glabratus Eichhoff) (1). Since the initial detection of the redbay ambrosia beetle near Savannah, GA in 2002, laurel wilt has caused widespread mortality of redbay in Georgia, South Carolina, and Florida (1). In September 2007, an avocado (Persea americana Mill.) tree planted approximately 10 years earlier in a residential neighborhood in Jacksonville, FL was discovered to be infected with laurel wilt. The crown was in various stages of decline, including upper branches that were dead and leafless, those with wilted and drooping foliage, and those with healthy foliage. Removal of bark from wilted branch sections revealed black-to-brown streaks of discoloration in the sapwood and a few ambrosia beetle holes from which the di...
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June 2008, Volume 92, Number 6
Page 976
http://dx.doi.org/10.1094/PDIS-92-6-0976A
Disease Notes
First Report of Laurel Wilt
Disease Caused by a Raffaelea
sp. on Avocado in Florida
A. E. Mayfield, III, Florida Department of Agriculture and
Consumer Services, Division of Forestry, Gainesville 32608; and
J. A. Smith, M. Hughes, and T. J. Dreaden, School of Forest
Resources and Conservation, University of Florida, Gainesville
32611
Open Access.
Laurel wilt is a vascular disease of redbay (Persea borbonia (L.)
Spreng.) and other plants in the family Lauraceae in the
southeastern United States. It is caused by a fungus (Raffaelea sp.)
that is vectored by a non-native insect of Asian origin, the redbay
ambrosia beetle (Xyleborus glabratus Eichhoff) (1). Since the
initial detection of the redbay ambrosia beetle near Savannah, GA
in 2002, laurel wilt has caused widespread mortality of redbay in
Georgia, South Carolina, and Florida (1). In September 2007, an
avocado (Persea americana Mill.) tree planted approximately 10
years earlier in a residential neighborhood in Jacksonville, FL was
discovered to be infected with laurel wilt. The crown was in
various stages of decline, including upper branches that were dead
and leafless, those with wilted and drooping foliage, and those
with healthy foliage. Removal of bark from wilted branch sections
revealed black-to-brown streaks of discoloration in the sapwood
and a few ambrosia beetle holes from which the discoloration
extended into the adjacent wood. A Raffaelea sp. was isolated
from discolored wood samples by surface sterilizing wood chips
by submersion in a 5% sodium hypochlorite solution for 30 s and
plating them on cycloheximide streptomycin malt agar (2). Small
subunit (18S) sequences from the rDNA were amplified by PCR
and sequenced with primers NS1 and NS4 (3). BLASTn searches
revealed homology to Raffaelea sp. C2203 (GenBank Accession
No. EU123076, 100% similarity, e-value of 0.0, and a total score
of 1,886), which is known to be the causal agent of laurel wilt (1).
The small-subunit rDNA sequence for this isolate has been
deposited into GenBank and has been assigned accession No.
EU257806. Pathogenicity of the laurel wilt pathogen on Persea
spp. in growth chamber trials has been previously demonstrated
(1). Laurel wilt is of concern to the commercial avocado industry
and is a potential threat to the Lauraceae elsewhere in the
Americas.
References: (1) S. W. Fraedrich et al. Plant Dis. 92:215, 2008. (2)
T. C. Harrington. Mycologia 73:1123, 1981. (3) T. J. White et al.
Page 315 in: PCR Protocols, a Guide to Methods and
Applications. M. A. Innis et al., eds. Academic Press, San Diego,
CA, 1990.
... Harr., Fraedrich & Aghayeva) Z.W. de Beer & M. Procter (formerly Raffaelea lauricola) (Ascomycota, Ophiostomatales) which causes a lethal vascular disease known as laurel wilt. This disease affects numerous species in the Lauraceae family, including bay laurel (Mayfield et al. 2008;Hughes et al. 2014Hughes et al. , 2017Eaton et al. 2023). This fungus has rapidly spread across the United States vectored by several species of ambrosia beetles, particularly Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae), commonly known as the redbay ambrosia beetle . ...
Thyridium lauri sp. nov. (Thyridiaceae, Thyridiales): a new pathogenic fungal species of bay laurel from Italy
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Laurus nobilis is an important Mediterranean tree and shrub native to Italy that is also commercially grown as spice and ornamental plant. Field surveys conducted since 2021 in Sicily (Italy) revealed that bay laurel plants in urban and private gardens and nurseries were severely affected by symptoms of stem blight and internal necrosis, which were associated with ambrosia beetle entry holes in the bark and internal wood galleries. The occurring ambrosia beetle was identified as Xylosandrus compactus, an invasive wood-boring pest previously reported from Sicily. Investigation of fungi from symptomatic tissues primarily resulted in the isolation of Thyridium-like colonies. The main symbiont of X. compactus, Ambrosiella xylebori, was also isolated from infested plants. Phylogenetic analyses of a combined matrix of ITS, LSU, act1, rpb2, tef1, and tub2 gene regions revealed that the isolated Thyridium-like colonies represent a new fungal species within the genus Thyridium. Based on both phylogeny and morphology, the new isolated fungus is described as Thyridium laurisp. nov. Moreover, two recently described species, Phialemoniopsis hipposidericola and Phialemoniopsis xishuangbannaensis, are transferred to the genus Thyridium due to the confirmed synonymy of both genera, as supported by molecular phylogenies. Pathogenicity test conducted on potted plants demonstrated that T. lauri is pathogenic to bay laurel, causing internal necrosis and stem blight. The new species was consistently re-isolated from the symptomatic tissue beyond the inoculation point, thereby fulfilling Koch’s postulates. This study represents the first report of a new pathogenic fungus, T. lauri, causing stem blight and internal necrosis of bay laurel plants and associated with infestation of the invasive ambrosia beetle X. compactus.
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... Scientific studies have documented how these species disperse intercontinental, negatively affecting local communities. Laurel Wilt Disease has extirpated populations of Lauraceae species across the southeastern United States, including Persea borbonia L. Spreng., Persea palustris Raf., Lindera benzoin (L.) Blume, Sassafras albidum (Nuttall) Nees, Persea americana Mill, affecting coastal lowland ecosystems from North Carolina to Texas [36,83,84]. These invasions can alter the composition of native communities and compete with native species for essential resources, resulting in decreased biodiversity and changes in ecosystem structure [85]. ...
The Biology, Impact, and Management of Xyleborus Beetles: A Comprehensive Review
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Simple Summary: Xyleborus beetles are tiny insects that impact forests and agriculture. These beetles burrow into trees and crops, causing damage that affects both the environment and the economy. This review aims to provide a clear understanding of the biology and behavior of Xyleborus beetles , including their life cycle, habitat, and feeding habits. We also discuss the various methods currently used to manage and control these pests, such as chemical treatments, biological controls, and integrated pest management strategies. By highlighting recent scientific advancements and identifying future research needs, this review offers insights for researchers, farmers, and policymakers. Understanding and effectively managing Xyleborus beetles is crucial for protecting our forests and agricultural resources, ultimately benefiting society by reducing economic losses and preserving ecological balance. Abstract: Xyleborus beetles, a diverse group of ambrosia beetles, present challenges to forestry and agriculture due to their damaging burrowing behavior and symbiotic relationships with fungi. This review synthesizes current knowledge on the biology, ecology, and management of Xyleborus. We explore the beetles' life cycle, reproductive strategies, habitat preferences, and feeding habits, emphasizing their ecological and economic impacts. Control and management strategies, including preventive measures, chemical and biological control, and integrated pest management (IPM), are critically evaluated. Recent advances in molecular genetics and behavioral studies offer insights into genetic diversity, population structure, and host selection mechanisms. Despite progress, managing Xyleborus effectively remains challenging. This review identifies future research needs and highlights innovative control methods, such as biopesticides and pheromone-based trapping systems.
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... Mortality has been reported in multiple Lauraceae hosts occurring in North America, including Persea palustris (swamp bay) Olatinwo et al. 2019); Litsea aestivalis L. 'Fern' (pondspice) (Hughes et al. 2011); Lindera benzoin L. 'Blume' (spicebush) (Fraedrich et al. 2016;Olatinwo et al. 2021); Sassafras albidum Nutt. (sassafras) (Smith et al. 2009;Riggins et al. 2011;Bates et al. 2013;Cameron et al. 2015;Fraedrich et al. 2015;Mayfield et al. 2019); Cinnamomum camphora (camphor tree) (Smith et al. 2009); and the economically important Persea americana Mill (avocado) (Mayfield et al. 2008b;Ploetz et al. 2017). ...
Efficacy of Propiconazole for Prevention of Sassafras Mortality from Laurel Wilt Disease Using a Tree Micro-Injection and Micro-Infusion Delivery System
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  • Jan 2023
Laurel wilt is a lethal disease of American Lauraceae caused by Harringtonia lauricola. Propiconazole is a systemic fungicide which arrests fungal growth among a variety of plant hosts. Propiconazole as a preventive treatment against laurel wilt in sassafras (Sassafras albidum) has not been evaluated. We treated sassafras trees with propiconazole using the Arborjet QUIK-jet® Micro-InjectionTM and TREE I.V. Micro-InfusionTM systems (Arborjet,Inc., Woburn, MA, USA) and challenged trees by inoculating them with H. lauricola. Out of 7 trees treated using the QUIK-jet Micro-Injection system, 6 (86%) survived 52 or more weeks following inoculation with H. lauricola, while only 11% of inoculated control trees (1 of 9) survived over this period. All trees not damaged by hurricanes (n = 13) treated with propiconazole using the TREE I.V. Micro-Infusion system survived signifi cantly longer than untreated control trees after inoculation with H. lauricola; 10 of 13 trees (77%) survived with < 50% crown loss, and 8 of 13 trees (62%) appeared entirely healthy 54 weeks post-inoculation. In the TREE I.V. Micro-Infusion system trial, 15 of 19 control trees (79%) had either died or lost ≥ 50% of living crown 54 weeks post-inoculation with H. lauricola. Results indicate sassafras trees treated with propiconazole using the Arborjet QUIK-jet Micro-Injection and TREE I.V. Micro-Infusion systems are significantly less likely to die within one year of infection with H. lauricola; however some trees may exhibit signifi cant crown decline (≥ 50%) over this period.
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... Among these fungi, Raffaelea species potentially contributed several observed mass tree mortality events [56][57][58][59]. Laurel wilt disease due to R. lauricola has caused widespread mortality of several tree species in the family Lauraceae, including avocado in the southeastern United States [60,61]. The impacts of several Raffaelea species were considered black swan events (an unpredictable event that is beyond what is normally expected) in tree pathology given that pathogenicity of Raffaelea species was either shown to be weak or not proven by artificial inoculation experiments [62]. ...
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... By November 2021, LWD had been reported in 12 states: Alabama (Bates et al. 2013), Arkansas (Olatinwo et al. 2016), Florida Hughes et al. 2011Hughes et al. , 2012Hughes et al. , 2014Mayfield et al. 2008;Ploetz et al. 2011b;Smith et al. 2009a, b), Georgia Smith et al. 2009b of Lauraceae species in the United States and the current distribution of LWD are presented in Figure 2. A map with the distribution of LWD in the United States updated by Forest Health, Southern Regional Extension Forestry (2021), can be found at http://southernfores thealth.net/diseases/laurel-wilt/distribution-map. ...
A Diagnostic Guide for Laurel Wilt Disease in Avocado
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  • Plant Health Progr
Laurel wilt disease (LWD), caused by the ambrosia fungus Raffaelea lauricola, is a deadly vascular disease affecting numerous hosts in the Lauraceae family, including important forest species and avocado trees. The fungal pathogen is spread by beetle-vectors and through root grafts. Symptoms include leaf wilting, foliar desiccation, stem and limb dieback, and depending on the host, localized or systemic vascular damage. R. lauricola and its main vector, Xyleborus glabratus (Redbay Ambrosia Beetle), are invasive species that were introduced into the United States in 2002. This guide describes methods used to diagnose LWD in avocado. R. lauricola is isolated from infected sapwood or ambrosia beetles using the semi-selective medium CSMA (cycloheximide–streptomycin malt agar). Molecular identification is based on the amplification of the LSU (Large Subunit of the ribosomal cassette) or of the species-specific microsatellites IFW and CHK by conventional PCR. More current detection methods use DNA extracted directly from infected material and include the amplification of specific DNA regions through conventional PCR, qPCR, or LAMP. However, to date, there is no method that can detect the pathogen early in the infection process (<3 days) when the vascular tissue remains asymptomatic. Besides detailed protocols on how to diagnose the disease and confirm the presence of the causal agent, we include protocols on pathogen preservation and inoculation. Although this guide focuses on avocado, the techniques included here can be implemented to diagnose LWD in other susceptible species.
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Presence of the causal agent of laurel wilt disease in sassafras-associated insects
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Full-text available
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Raffaelea lauricola (laurel wilt)
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This datasheet on Raffaelea lauricola covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Vectors & Intermediate Hosts, Diagnosis, Biology & Ecology, Environmental Requirements, Seedborne Aspects, Impacts, Prevention/Control, Further Information.
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Assessing the Survival of the Redbay Ambrosia Beetle and Laurel Wilt Pathogen in Wood Chips: FOR289/FR351, 11/2011
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What is the best way for homeowners to dispose of dead redbay trees to avoid spreading laurel wilt? This 4-page fact sheet summarizes a UF/IFAS study providing evidence that a simple technique — chipping the dead trees — can help contain the disease within a small area and that there is a low probability of long-distance movement of LW via wood chips. Written by Don Spence, Jason Smith, Albert Mayfield III, Jiri Huler, Randy Ploetz, and Lukasz Stelinski, and published by the UF Department of School of Forest Resources and Conservation, November 2011. Reviewed August 2014.
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A Fungal Symbiont of the Redbay Ambrosia Beetle Causes a Lethal Wilt in Redbay and Other Lauraceae in the Southeastern United States
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Extensive mortality of redbay has been observed in the coastal plain counties of Georgia and southeastern South Carolina since 2003 and northeastern Florida since 2005. We show that the redbay mortality is due to a vascular wilt disease caused by an undescribed Raffaelea sp. that is a fungal symbiont of Xyleborus glabratus, an exotic ambrosia beetle. Trees affected by the disease exhibit wilt symptoms that include a black discoloration of the sapwood. Redbay trees and containerized seedlings died within 5 to 12 weeks after inoculation with the Raffaelea sp. When redbay seedlings were challenged with X. glabratus, the beetles tunneled into 96% of the plants, 70% died, and the Raffaelea sp. was recovered from 91%. X. glabratus and the Raffaelea sp. have also been associated with mortality of sassafras, and the Raffaelea sp. has been isolated from wilted pondberry and pondspice. Additional inoculation studies have shown that the Raffaelea sp. is pathogenic to sassafras, spicebush, and avocado, but not to red maple. Female adults of X. glabratus have paired mycangia near the mandibles, and the Raffaelea sp. is routinely isolated from the heads of beetles. The fungus is apparently introduced into healthy redbay during beetle attacks on stems and branches. The wilt currently affecting redbay and sassafras represents a major threat to other members of the Lauraceae indigenous to the Americas, including avocado in commercial production.
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