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First Occurrence of Laurel Wilt Disease Caused by Raffaelea lauricola on Redbay Trees in Mississippi

Authors:
John J Riggins at Mississippi State University
John J Riggins
Marc A. Hughes at US Forest Service
Marc A. Hughes
Jason Andrew Smith at University of Mount Union
Jason Andrew Smith
A. E. Mayfield
A. E. Mayfield
A. E. Mayfield
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Abstract

Laurel wilt is a lethal, nonnative vascular wilt disease of redbay (Persea borbonia), sassafras (Sassafras albidum), and other trees in the Lauraceae (1,4). It is caused by a fungus (Raffaelea lauricola) and transmitted by the redbay ambrosia beetle (Xyleborus glabratus), a nonnative insect first detected in Georgia in 2002 (1,2). Since introduction of the pathogen and vector (presumably from Asia), laurel wilt has caused extensive mortality to redbays in Georgia, Florida, and South Carolina (1). In June 2009, a landowner in Gautier, MS reported dead redbay trees. Signs and symptoms were identical to those reported for laurel wilt along the Atlantic Coast (wilted, bronze red foliage, and dark gray-to-black vascular discoloration) (1). Infected trees have subsequently been confirmed in and near the Pascagoula River Basin. Size of infected redbays ranged from 5 to 20 cm (diameter at breast height). No heavily decomposed or fallen redbays were noted. Many individual specimens exhibited extensive drying of stem wood and dry, wilted, light brown foliage. This indicates that introduction to the area may have occurred within the last 3 years. X. glabratus adults were collected (30°26′44.45″N, 88°39′41.83″W) in a Lindgren funnel trap baited with phoebe and manuka oil lures. Beetle identification was confirmed by USDA-APHIS, and voucher specimens were submitted to the Smithsonian National Museum of Natural History and the Mississippi Entomological Museum. Symptomatic redbay wood chips from the same location were surface sterilized and plated on cycloheximide-streptomycin malt agar and R. lauricola was isolated. A 1,026-bp portion of 18S rDNA (GenBank No. GQ996063) was amplified by PCR and sequenced using primers NS1 and NS4. BLASTn searches revealed perfect homology to R. lauricola isolate PL 697 (GQ329704). Two isolates of R. lauricola were recovered and prepared into separate spore suspensions (1 × 10 ⁸ CFU/ml). Each isolate was inoculated into two healthy redbays. The inoculated redbays were placed in a growth chamber with two water-only controls. All inoculated plants, and none of the controls, exhibited wilt symptoms and died within 20 days. R. lauricola was recovered from the discolored sapwood of the inoculated plants, completing Koch's postulates. A model prediction for the natural dispersion of X. glabratus and R. lauricola estimated that these organisms may not reach Mississippi for 10 to 15 years (3). The current detection of laurel wilt in Mississippi is substantially ahead of this estimate. Currently, no records of laurel wilt have been reported from western Georgia, all of Alabama, or the panhandle of Florida. Confirmed locations in Mississippi are in Jackson County, along the Interstate 10 corridor and the Pascagoula River drainage. Due to the relatively large extent of the infestation (~64 km ² , including hundreds of infected trees) eradication is not being attempted. Surveys, remote sensing, and phylogeographic analysis are underway to delineate the extent of infestation and discover the mode of introduction. The current outbreak of laurel wilt in Mississippi is likely the result of human transport of infested wood, either from Asia as a separate, new introduction or from previously infested areas in the southeastern United States. References: (1) S. W Fraedrich et al. Plant Dis. 92:215, 2008. (2) T. C. Harrington et al. Mycotaxon 104:399, 2008. (3) F. Koch and W. Smith. Environ. Entomol. 37:442, 2008. (4) J. A. Smith et al. Plant Dis. 93:198, 2009.
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May 2010, Volume 94, Number 5
Page 634
http://dx.doi.org/10.1094/PDIS-94-5-0634C
Disease Notes
First Occurrence of Laurel
Wilt Disease Caused by
Raffaelea lauricola on Redbay
Trees in Mississippi
J. J. Riggins, Department of Entomology and Plant Pathology,
Mississippi State University, Mississippi State 39762; M. Hughes,
Department of Plant Pathology, University of Florida, Gainesville
32611; J. A. Smith, School of Forest Resources and Conservation,
University of Florida, Gainesville 32611; A. E. Mayfield, III,
USDA Forest Service Southern Research Station, Asheville, NC
28806; and B. Layton, C. Balbalian, and R. Campbell, Department
of Entomology and Plant Pathology, Mississippi State University,
Mississippi State 39762. Approved for publication as Article No.
A-11714 of the Mississippi Agricultural and Forestry Experiment
Station
Open Access.
Laurel wilt is a lethal, nonnative vascular wilt disease of redbay
(Persea borbonia), sassafras (Sassafras albidum), and other trees
in the Lauraceae (1,4). It is caused by a fungus (Raffaelea
lauricola) and transmitted by the redbay ambrosia beetle
(Xyleborus glabratus), a nonnative insect first detected in Georgia
in 2002 (1,2). Since introduction of the pathogen and vector
(presumably from Asia), laurel wilt has caused extensive mortality
to redbays in Georgia, Florida, and South Carolina (1). In June
2009, a landowner in Gautier, MS reported dead redbay trees.
Signs and symptoms were identical to those reported for laurel
wilt along the Atlantic Coast (wilted, bronze red foliage, and dark
gray-to-black vascular discoloration) (1). Infected trees have
subsequently been confirmed in and near the Pascagoula River
Basin. Size of infected redbays ranged from 5 to 20 cm (diameter
at breast height). No heavily decomposed or fallen redbays were
noted. Many individual specimens exhibited extensive drying of
stem wood and dry, wilted, light brown foliage. This indicates that
introduction to the area may have occurred within the last 3 years.
X. glabratus adults were collected (30°26′44.45″N,
88°39′41.83″W) in a Lindgren funnel trap baited with phoebe and
manuka oil lures. Beetle identification was confirmed by USDA-
APHIS, and voucher specimens were submitted to the
Smithsonian National Museum of Natural History and the
Mississippi Entomological Museum. Symptomatic redbay wood
chips from the same location were surface sterilized and plated on
cycloheximide-streptomycin malt agar and R. lauricola was
isolated. A 1,026-bp portion of 18S rDNA (GenBank No.
GQ996063) was amplified by PCR and sequenced using primers
NS1 and NS4. BLASTn searches revealed perfect homology to R.
lauricola isolate PL 697 (GQ329704). Two isolates of R. lauricola
were recovered and prepared into separate spore suspensions (1 ×
108 CFU/ml). Each isolate was inoculated into two healthy
redbays. The inoculated redbays were placed in a growth chamber
with two water-only controls. All inoculated plants, and none of
the controls, exhibited wilt symptoms and died within 20 days. R.
lauricola was recovered from the discolored sapwood of the
inoculated plants, completing Koch's postulates. A model
prediction for the natural dispersion of X. glabratus and R.
lauricola estimated that these organisms may not reach
Mississippi for 10 to 15 years (3). The current detection of laurel
wilt in Mississippi is substantially ahead of this estimate.
Currently, no records of laurel wilt have been reported from
western Georgia, all of Alabama, or the panhandle of Florida.
Confirmed locations in Mississippi are in Jackson County, along
the Interstate 10 corridor and the Pascagoula River drainage. Due
to the relatively large extent of the infestation (~64 km2, including
hundreds of infected trees) eradication is not being attempted.
Surveys, remote sensing, and phylogeographic analysis are
underway to delineate the extent of infestation and discover the
mode of introduction. The current outbreak of laurel wilt in
Mississippi is likely the result of human transport of infested
wood, either from Asia as a separate, new introduction or from
previously infested areas in the southeastern United States.
References: (1) S. W Fraedrich et al. Plant Dis. 92:215, 2008. (2)
T. C. Harrington et al. Mycotaxon 104:399, 2008. (3) F. Koch and
W. Smith. Environ. Entomol. 37:442, 2008. (4) J. A. Smith et al.
Plant Dis. 93:198, 2009.
... Native species that have succumbed to natural infections include: redbay (Persea borbonia (L.) Spreng.) Menard et al. 2016;Riggins et al. 2010), pondspice (Litsea aestivalis (L.) Spreng.) (Fraedrich et al. ...
... ),Kentucky (Loyd et al. 2020), Louisiana(Fraedrich et al. 2015b;Olatinwo et al. 2019Olatinwo et al. , 2021, Mississippi(Riggins et al. 2010(Riggins et al. , 2011, North Carolina (Mayfield et al. 2019), South Carolina (Fraedrich et al. 2008, 2016; Smith et al. 2009a), Tennessee (Loyd et al. 2020), Texas (Menard et al. 2016), and Virginia (Virginia Department of Forestry 2021). The distribution FIGURE 2U.S. map showing counties containing native and introduced species of Lauraceae (green) and counties where laurel wilt disease (LWD) has been confirmed (red). ...
A Diagnostic Guide for Laurel Wilt Disease in Avocado
Article
  • Mar 2022
  • 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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... North America is likely due to several factors. First, trapping networks suggest that adult female X. glabratus can disperse hundreds of metres (Hanula et al., 2016), and laurel wilt has been found hundreds of kilometres from the nearest known outbreak (Bates et al., 2013;Cameron et al., 2008;Fraedrich, Johnson, et al., 2015;Olatinwo et al., 2016;Riggins et al., 2010). Second, anthropogenic spread (e.g., movement of infested firewood) has been strongly implicated as a contributing factor to the range expansions of X. glabratus (Ploetz, Kendra, Choudhury, et al., 2017). ...
Risk assessment of Hass avocado and Mexican Lauraceae for attack by redbay ambrosia beetle (Coleoptera: Curculionidae: Scolytinae)
Article
Full-text available
  • Jan 2023
The redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), vectors the mycopathogen that causes laurel wilt, a lethal vascular disease of trees in the Lauraceae. Since being detected in Georgia, USA in 2002, this invasive pest has become established in 11 additional states. With continued spread, X. glabratus will likely enter Mexico. In advance of this event, this study was initiated to assess the risk posed to eight native laurels and Hass avocados, the predominant cultivar grown in Mexico. Wood bolts from each species were used in (a) field tests to determine the relative attraction of female X. glabratus , (b) laboratory bioassays to evaluate boring preferences, and (c) GC–MS analyses to identify host kairomones. For comparison, tests included control bolt treatments consisting of silkbay (an attractive U.S. laurel) and Simmonds avocado (a Florida cultivar susceptible to laurel wilt). Hass avocado and two native laurels ( Persea schiedeana and Ocotea heribertoi vel aff.) were highly attractive to females and elicited strong boring responses. These species were high in sesquiterpene hydrocarbons, including α‐copaene and α‐cubebene. Results of this study suggest that X. glabratus could become a serious agricultural and forest pest upon incursion into Mexico, with severe economic and ecological impacts.
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... These reporting efforts are passive and not achieved through targeted aerial surveys aimed at detecting new infestations. Although laurel wilt is a highly virulent disease that can kill naïve North American host trees such as redbay and sassafras within weeks of initial infection Olatinwo et al. 2021), there is potentially a lag between establishment and detection in a county (Riggins et al. 2010) for which we were unable to account. For example, laurel wilt could have been in a county for multiple years prior to someone (e.g., a forest health specialist or landowner) noticing the disease symptoms, with detection lags potentially owing to limitations of resources for surveys and/or reporting lags by non-specialists. ...
Drivers of invasion by laurel wilt of redbay and sassafras in the southeastern US
Article
Full-text available
  • Dec 2022
  • LANDSCAPE ECOL
Context Timely responses to mitigate economic and environmental impacts from invading species are facilitated by knowledge of the speed and drivers of invasions. Objective Quantify changes in invasion patterns through time and factors that governed time-to-invasion by laurel wilt, one of the most damaging, non-native disturbance agents invading forests of the United States. Methods We analyzed county-level occurrence data (2004–2021) for laurel wilt across the southeastern United States. A Cox proportional hazards modeling framework was used to elucidate drivers of invasion. Results As of 2021, laurel wilt had been detected in 275 counties and made 72 discrete jumps (averaging 164 km ± 16 SE) into counties that did not share a border with a previously invaded county. Spread decelerated from 40 km/yr to 24 km/yr after 5 years, with a marked decline in the number of counties invaded in 2021 (16) compared with 2020 (33). The Cox proportional hazards model indicated that proxies for anthropogenic movement and habitat invasibility increased invasion risk. Conclusion The recent decline in number of counties invaded could be due to disruptions to travel and/or surveys from the coronavirus pandemic, but exhaustion of the most suitable habitat, such as counties in the southeastern US with warm annual temperatures and high densities of host trees, could have also contributed to this trend. This work suggests that without a shift in spread driven by additional insect vectors, that rates of range expansion by laurel wilt might have peaked in 2020 and could continue decelerating.
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... Movement of infested wood materials by private citizens and by industry likely plays a significant role in the spread of the laurel wilt pathogen and X. glabratus over short as well as long distances. Numerous instances have occurred where the disease has been found hundreds of kilometers from previously known disease fronts, and movement of infected wood has long been suspected as the cause [13,68,[130][131][132]. During the early stages of the laurel wilt epidemic, new spots of infected trees were commonly located many miles from sites with disease along major roads and train tracks where logs and other unprocessed woody materials were transported. ...
Laurel Wilt: Current and Potential Impacts and Possibilities for Prevention and Management
Article
Full-text available
  • Feb 2021
In recent years, outbreaks of nonnative invasive insects and pathogens have caused significant levels of tree mortality and disturbance in various forest ecosystems throughout the United States. Laurel wilt, caused by the pathogen Raffaelea lauricola (T.C. Harr., Fraedrich and Aghayeva) and the primary vector, the redbay ambrosia beetle (Xyleborus glabratus Eichhoff), is a nonnative pest-disease complex first reported in the southeastern United States in 2002. Since then, it has spread across eleven southeastern states to date, killing hundreds of millions of trees in the plant family Lauraceae. Here, we examine the impacts of laurel wilt on selected vulnerable Lauraceae in the United States and discuss management methods for limiting geographic expansion and reducing impact. Although about 13 species belonging to the Lauraceae are indigenous to the United States, the highly susceptible members of the family to laurel wilt are the large tree species including redbay (Persea borbonia (L.) Spreng) and sassafras (Sassafras albidum (Nutt.) Nees), with a significant economic impact on the commercial production of avocado (Persea americana Mill.), an important species native to Central America grown in the United States. Preventing new introductions and mitigating the impact of previously introduced nonnative species are critically important to decelerate losses of forest habitat, genetic diversity, and overall ecosystem value.
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... As this disease has spread, others have noted large jumps in its distribution. Riggins et al [172] reported a laurel wilt outbreak in Mississippi, over 500 km from the nearest known outbreak, and a recent finding in Texas was 300 km from the nearest known occurrence [16]. The above findings have been on redbay, but sassafras has also been impacted. ...
Laurel Wilt in Natural and Agricultural Ecosystems: Understanding the Drivers and Scales of Complex Pathosystems
Article
Full-text available
  • Feb 2017
Laurel wilt kills members of the Lauraceae plant family in the southeastern United States. It is caused by Raffaelea lauricola T.C. Harr., Fraedrich and Aghayeva, a nutritional fungal symbiont of an invasive Asian ambrosia beetle, Xyleborus glabratus Eichhoff, which was detected in Port Wentworth, Georgia, in 2002. The beetle is the primary vector of R. lauricola in forests along the southeastern coastal plain of the United States, but other ambrosia beetle species that obtained the pathogen after the initial introduction may play a role in the avocado (Persea americana Miller) pathosystem. Susceptible taxa are naïve (new-encounter) hosts that originated outside Asia. In the southeastern United States, over 300 million trees of redbay (P. borbonia (L.) Spreng.) have been lost, and other North American endemics, non-Asian ornamentals and avocado—an important crop that originated in MesoAmerica—are also affected. However, there are no reports of laurel wilt on the significant number of lauraceous endemics that occur in the Asian homeland of R. lauricola and X. glabratus; coevolved resistance to the disease in the region has been hypothesized. The rapid spread of laurel wilt in the United States is due to an efficient vector, X. glabratus, and the movement of wood infested with the insect and pathogen. These factors, the absence of fully resistant genotypes, and the paucity of effective control measures severely constrain the disease’s management in forest ecosystems and avocado production areas.
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... Within this reserve, P. borbonia is often a common sub-canopy component of maritime forests; density of P. borbonia at our study site was 325 trees (C2.5 DBH) ha -1 [determined from point-centered quarter method (Mitchell 2001)]. Laurel wilt disease was first reported in Jackson County, Mississippi in 2009 near Sandhill Crane National Wildlife Refuge (Riggins et al. 2010) and infected trees were first observed on the GBNERR in early 2014. We targeted an area within GBNERR where P. borbonia was abundant and the invasion of LWD imminent. ...
Sprouting capacity of Persea borbonia and maritime forest community response to simulated laurel wilt disease
Article
Full-text available
  • Apr 2017
  • PLANT ECOL
There are numerous examples of how exotic insect pests and pathogens have altered the dominance of native tree species. Changes to the structure of associated communities will depend on whether the affected species survives and if so, the degree to which it is diminished. In the southeastern USA, Persea borbonia, a common tree found in many coastal plain habitats, is the primary host of laurel wilt disease (LWD); infection rates and main-stem mortality are catastrophically high (>90%) in invaded populations. We simulated the effects of LWD prior to its arrival in coastal Mississippi by girdling and then removing the main stems of P. borbonia trees. Over a 2-year period, we monitored P. borbonia persistence via basal resprouts, understory light availability, and community structure. Removal of P. borbonia main stems resulted in a 50% increase in light transmission (measured at 1 m above ground level). All treated individuals produced basal resprouts, the size and number of which were positively related to initial tree girth. Post-treatment increases in basal area were greatest for the sub-canopy species, Ilex vomitoria, and were significantly higher in treatment versus control plots. Woody seedlings and herbaceous plants showed no significant trends in composition and abundance over time or between control and treatment plots. Our results suggest that removal of P. borbonia and subsequent resprouting causes shifts in P. borbonia size class frequencies and sub-canopy species dominance but has negligible impacts on understory plant community dynamics.
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... Initial reports in new states were on redbay [Mississippi (Riggins et al. 2010), North Carolina (Hughes et al. 2015), and Texas (Menard et al. 2016)] or on sassafras [Alabama , Louisiana (Fraedrich et al. 2015a), and Arkansas (Olatinwo et al. 2016)]. However, all tested American Lauraceae have been shown to be susceptible to laurel wilt in inoculation studies Hughes et al. 2013;Ploetz and Konkol 2013). ...
Genetic variation in native populations of the laurel wilt pathogen, Raffaelea lauricola, in Taiwan and Japan and the introduced population in the USA
Article
  • Dec 2017
  • PLANT DIS
Laurel wilt is a vascular wilt disease caused by Raffaelea lauricola, a mycangial symbiont of an ambrosia beetle, Xyleborus glabratus. The fungus and vector are native to Asia but were apparently introduced to the Savannah, GA, area 15 or more years ago. Laurel wilt has caused widespread mortality on redbay (Persea borbonia) and other members of the Lauraceae in the southeastern United States, and the pathogen and vector have spread as far as Texas. Although believed to be a single introduction, there has been no extensive study on genetic variation of R. lauricola populations that would suggest a genetic bottleneck in the United States. Ten isolates of R. lauricola from Japan, 55 from Taiwan, and 125 from the United States were analyzed with microsatellite and 28S rDNA markers, and with primers developed for two mating-type genes. The new primers identified isolates as either MAT1 or MAT2 mating types in roughly equal proportions in Taiwan and Japan, where there was also high genetic diversity within populations based on all the markers, suggesting that these populations may have cryptic sex. Aside from a local population near Savannah and a single isolate in Alabama that had unique microsatellite alleles, the U.S. population was genetically uniform and included only the MAT2 mating type, supporting the single introduction hypothesis. This study suggests the importance of preventing a second introduction of R. lauricola to the United States, which could introduce the opposite mating type and allow for genetic recombination. © 2017, American Phytopathological Society. All rights reserved.
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... The original models for the spread of laurel wilt predicted that the disease would not reach central Louisiana until at least 2030 (Koch & Smith 2008); however, these models could not predict anthropogenic movement of the beetle in wood. Solid wood packing material is believed to have been the pathway for the introduction of X. glabratus and R. lauricola into the USA, and the subsequent movement of infested wood has been suspected as the cause for many of the longdistance "jumps" in the distribution of the vector and pathogen as they have moved throughout the southeastern USA Riggins et al. 2010;Ploetz et al. 2011;Bates et al. 2013). ...
First Report of Xyleborus glabratus (Coleoptera: Curculionidae: Scolytinae) and Laurel Wilt in Louisiana, USA: The Disease Continues Westward on Sassafras
Article
Full-text available
  • Dec 2015
Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae) and sassafras trees that died from laurel wilt were discovered in a 3-parish area of northern Louisiana, USA, in Sep 2014. Redbay, a species that has been severely affected by the disease in the coastal plains forests of the southeastern USA, is not found in this area of northern Louisiana, suggesting that sassafras is attractive to X. glabratus and an adequate reproductive host for the beetle. This is the first report of X. glabratus and laurel wilt in Louisiana and the first report of the beetle and disease west of the Mississippi River.
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Raffaelea lauricola (laurel wilt)
Article
  • Jan 2022
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
Article
  • Dec 2011
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
Article
Full-text available
  • Feb 2008
  • PLANT DIS
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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First Report of Laurel Wilt Disease Caused by Raffaelea lauricola on Camphor in Florida and Georgia
Article
  • Feb 2009
  • PLANT DIS
Laurel wilt is a recently described (1) vascular disease of redbay (Persea borbonia (L.) Spreng) and other plants in the family Lauraceae. The wilt is caused by Raffaelea lauricola, a fungus vectored by the nonnative redbay ambrosia beetle (Xyleborus glabratus Eichhoff) (1,2). Since 2003, laurel wilt has caused widespread mortality of redbay in Georgia, South Carolina, and Florida (1) and has recently been found on avocado in Florida (4). Since June of 2007, wilted shoots and branch dieback have been observed in several camphor trees (Cinnamomum camphora (L.) Sieb.) in residential areas of McIntosh and Glynn counties in Georgia and Baker County in Florida. Symptomatic camphor trees ranged from 4.5 to 12 m high and occurred in areas where redbay mortality due to laurel wilt has been frequently observed during the last 2 to 3 years. In some camphor trees, only the smaller branches (<2 cm in diameter) were wilting or dead, whereas in other trees (e.g., Baker County, Florida), the larger branches and substant...
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Spatio-Temporal Analysis of Xyleborus glabratus (Coleoptera: Circulionidae: Scolytinae) Invasion in Eastern U.S. Forests
Article
  • Apr 2008
  • ENVIRON ENTOMOL
The non-native redbay ambrosia beetle, Xyleborus glabratus Eichhoff (Coleoptera: Curculionidae: Scolytinae), has recently emerged as a significant pest of southeastern U.S. coastal forests. Specifically, a fungal symbiont (Raffaelea sp.) of X. glabratus has caused mortality of redbay (Persea borbonia) and sassafras (Sassafras albidum) trees in the region; several other Lauraceae species also seem susceptible. Although the range of X. glabratus continues to expand rapidly, little is known about the species' biology and behavior. In turn, there has been no broad-scale assessment of the threat it poses to eastern U.S. forests. To provide a basic information framework, we performed analyses exploiting relevant spatio-temporal data available for X. glabratus. First, we mapped the densities of redbay and sassafras from forest inventory data. Second, we used climate matching to delineate potential geographic limits for X. glabratus. Third, we used county infestation data to estimate the rate of spread and modeled spread through time, incorporating host density as a weighting factor. Our results suggest that (1) key areas with high concentrations of redbay have yet to be invaded, but some are immediately threatened; (2) climatic conditions may serve to constrain X. glabratus to the southeastern U.S. coastal region; and (3) if unchecked, X. glabratus may spread throughout the range of redbay in <40 yr. Disruption of anthropogenic, long-distance dispersal could reduce the likelihood of this outcome.
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  • Jan 2008
  • PLANT DIS
  • 215
  • S Fraedrich
References: (1) S. W Fraedrich et al. Plant Dis. 92:215, 2008. (2)
  • Jan 2008
  • ENVIRON ENTOMOL
  • 442
  • C Harrington
C. Harrington et al. Mycotaxon 104:399, 2008. (3) F. Koch and W. Smith. Environ. Entomol. 37:442, 2008. (4) J. A. Smith et al. Plant Dis. 93:198, 2009.