November 10, 2010 - Two beetles
trapped in Mobile County, just north
of Grand Bay, have been confirmed as
redbay ambrosia beetles. The
specimens were collected and
identified by Dr. John Riggins from
Mississippi State University and
confirmed by the USDA Animal and
Plant Health Inspection Service
(APHIS), Plant Protection and
Quarantine (PPQ) section. This is
the first confirmation of the
presence of the beetle in Alabama.
INTRODUCTION: The redbay
ambrosia beetle, Xyleborus
glabratus Eichhoff, was first
detected in the US in a survey trap
near Port Wentworth, Georgia in 2002
(Rabaglia 2005). By 2003, this Asian
beetle and its associated fungus (Raffaelea
lauricola T. C. Harr.,
Fraedrich & Aghayeva) had caused
substantial mortality of redbay (Persea
borbonia (L.) Spreng.) within a
40-mile radius of the initial trap
detection (Douce and Johnson 2005),
but the cause of the mortality was
unknown at that time. By 2005,
Xyleborus glabratus was found
to be consistently associated with
unusual redbay and sassafras (Sassafras
albidum (Nutt.) Nees) mortality
in an expanded area of coastal South
Carolina and Georgia. In Florida,
unusual mortality of redbay was
first reported in the spring of 2005
at the Timucuan Ecological and
Historic Preserve in northern Duval
County, and the presence of X.
glabratus was confirmed at this site
in October 2005. Currently, the
range of X. glabratus and associated
redbay mortality continues to expand
in Florida and the coastal
Southeast. This ambrosia beetle
introduces a vascular fungus (Raffaelea
lauricola) into its host, causing
infected redbays and other hosts in
the Lauraceae to wilt and die within
a few weeks or months. This insect
and disease complex has collectively
been named “laurel
wilt” (Fraedrich et al. 2008).
Xyleborus glabratus is the
twelfth species of non-native
ambrosia beetle known to have become
established in the US since 1990.
All are suspected to have been
introduced in solid wood packing
materials, such as crates and
pallets (Haack 2003).
Xyleborus glabratus is a
small, elongate, cylindrical beetle
about 2 mm in length (Fig. 1). It is
very similar in appearance to the
dozen other members of the genus,
both native and exotic, already
found in Florida. The combination of
its almost blackish coloration,
nearly glabrous upper surface, and
abrupt apical declivity helps to
distinguish it from other Florida
species, but positive identification
will depend on examination by a
female. A) lateral view, B)
String of compacted ambrosia
beetle sawdust on redbay.
little is known about the biology of
X. glabratus at this time,
but it is probably similar to other
species in the genus. Like other
ambrosia beetles of the tribe
glabratus does not actually
feed on wood, but instead, adults
and larvae feed on fungi that are
inoculated into galleries in the
sapwood by the adult females. Fungal
spores are carried in specialized
structures (mycangia) found at the
base of each mandible (Fraedrich et
al. 2008). The generation time is
uncertain and likely to vary
according to temperature, but
observations indicate that brood
development can occur in 50-60 days
(Hanula et al. 2008). Males of
Xyleborus species are generally
dwarfed, haploid and flightless (Rabaglia
2005). The vascular wilt pathogen (Raffaelea
lauricola) recovered from infested
redbays is vectored by X.
glabratus. Most ambrosia
beetles attack stressed, dead or
dying woody plants, but a few -
notably several exotic species of
the genus Xylosandrus in
the southeastern U.S. - will attack
seemingly healthy trees and shrubs.
In the U.S., X. glabratus
has been shown to attack healthy
hosts. Although the flight activity
of X. glabratus tends to be
highest in the summer (Hanula et al.
2008), adult beetles have been
successfully flight trapped in low
numbers in Florida during both
winter and summer months (A.
Mayfield and J. Eickwort, FDACS,
COMMON HOSTS: Confirmed
hosts in the US at this time include
redbay and sassafras. The wilt
pathogen associated with X.
glabratus (Raeffaelea lauricola) has
also been recovered from: Persea
americana (avocado), P. borbonia (redbay),
P. palustris (swampbay), Sassafras
albidum (Sassafras), Litsea
aestivalis (pondspice), Lindera
melissifolia (pondberry) and
Cinnamomum camphora (Camphor) (
Mayfield et al. 2008a, Smith et al.
2009). Known host trees in Asia
include an Asian spicebush, Lindera
latifolia; yellow litsea, Litsea
elongata; and sal, Shorea robusta (Rabaglia
Trees freshly attacked by X.
glabratus exhibit few external
symptoms initially. Small strings of
compacted sawdust (Fig. 2) may
protrude from the bark at the point
of attack, but these strings
disintegrate easily and are not
always readily apparent. Removal of
bark at the point of attack reveals
shot-holes from which a dark stain
extends into the surrounding xylem
(Fig 3A). The stain is the tree’s
response to infection by the
Raffaelea lauricola fungus, which
gradually spreads through much of
the outer sapwood (Fig. 3B, C).
Attacked trees eventually exhibit
wilted foliage with a reddish or
purplish discoloration (Fig. 4A).
Foliar discoloration may occur first
within a section of the crown (e.g.,
major branch) or simultaneously
throughout the entire crown. The
foliage eventually turns brown and
tends to remain on the branches
(Fig. 4B). This wilt scenario is
more extensive than the isolated
branch “flagging” caused by the
black twig borer (Xylosandrus
compactus (Eichoff)), which commonly
kills twigs and outer portions of
small-diameter branches of redbay
(Dixon and Woodruff 1982). As the
host weakens and dies, it is
typically colonized by several other
species of ambrosia beetles,
including Xylosandrus crassiusculus
(Motschulsky), Monarthrum mali
(Fitch), Xyleborus affinus (Eichhoff),
and several others (Foltz et al
ECOLOGICAL AND ECONOMIC
IMPORTANCE: Given the
current pattern of redbay mortality
and the rapid range expansion of X.
glabratus, this non-native ambrosia
beetle and its associated fungus
have the potential to seriously
affect Lauraceous hosts in the
southeastern US. At the site of the
initial X. glabratus detection in
Florida, redbay mortality has
increased from 10% to more than 90%
in a period of only fifteen months (Fraedrich
et al. 2008). Areas near Hilton
Head, South Carolina have
experienced nearly complete
mortality of the local redbay
population. Redbay is important to
wildlife as its fruit, seed and/or
foliage are eaten by several species
of songbirds, wild turkeys, quail,
deer, and black bear (Brendemuehl
1990). Larvae of the Palamedes
swallowtail (Papilio palamedes
(Drury)) feed primarily on species
of Persea, thus this butterfly
species is likely to be negatively
impacted by X. glabratus. There is
also considerable concern about the
potential impact of laurel wilt on
avocado (P. americana), which is an
economically important crop in
Florida. Avocado trees have been
found infected with the R. lauricola
pathogen in the field, and
laboratory experiments have shown
that X. glabratus can successfully
bore into avocado trees and
introduce the pathogen (Mayfield et
al. 2008a, 2008b). However, it is
still uncertain what effect laurel
wilt will have once it reaches areas
of large-scale avocado production in
Xyleborus glabratus is native to
India (Assam, Bengal), Japan (and
the Bonin Islands), Myanmar and
Taiwan (Rabaglia 2005). The current
range in the southeastern US
includes most of the coastal and
adjacent inland counties in Georgia
and South Carolina. In Florida, X.
glabratus has been found in the
following counties: Alachua, Baker,
Bradford, Brevard, Citrus, Clay,
Columbia, Flagler, Indian River,
Marion, Martin, Nassau, Okeechobee,
Osceola, Putnam, St. Johns, St.
Lucie, Suwannee, Union and Volusia.
avoid spreading the beetle and
pathogen to new areas, wood or chips
from infested trees should
transported out of the local area
where the trees were found. Dead redbay or other Lauraceous tree
species cut in residential areas
should be chipped and left onsite as
mulch, or disposed of as locally as
possible. Redbay firewood should not
be transported. Personnel from
University of Florida-Institute for
Food and Agricultural Sciences
(UF-IFAS) are currently working on
chemical control options for red bay
Stained sapwood of redbay caused by
Raffaelea lauricola. Fungal
infection A) around Xyleborus
glabratus entrance holes, B) in
stem cross section, C) on lower stem
with bark removed.
Wilt symptoms of redbay attacked by
Xyleborus glabratus and
infected with Raffaelea
lauricola. A) Sections of crown
turning purple to red. B) Same tree
eight months later (May 2006).
The public can help
prevent the spread of the redbay
ambrosia beetle and laurel wilt
disease by following these
Become familiar with the signs
of laurel wilt disease and
redbay ambrosia beetle and be on
the lookout for evidence of the
pest/disease on your trees.
Use local firewood only – Do not
transport firewood from other
states because destructive pests
and diseases, such as redbay
ambrosia beetle and laurel wilt,
can hitchhike into Alabama on
Do not transport host trees (redbay,
swamp bay, avocado, sassafras,
pondspice, pondberry and others
in the Lauraceae family) unless
purchased from a registered
Avoid spreading the beetle and
pathogen to new areas - wood or
chips from infested trees should
not be transported out of the
local area where the trees were
found. Dead redbay or other
Lauraceous tree species cut in
residential areas should be
chipped and left onsite as
mulch, or disposed of as locally
as possible. Redbay firewood
should not be transported.
Florida Department of Agriculture
& Consumer Services, Division of
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Persea borbonia (L.) Spreng.
Redbay. Pp. 530-506 in R.M.
Burns and B.H. Honkala (eds.).
Silvics of North America, Volume 2,
Hardwoods. Agriculture Handbook 654,
USDA Forest Service, Washington, DC.
Dixon, W.N. and R.E.
Woodruff. 1982. The black
twig borer, Xylosandrus
compactus (Eichhoff) (Coleoptera:
Scolytidae). FL Dept. Agriculture
Consumer Serv., Div. Plant Industry
Ento. Circ. No. 250, 2p.
Douce, G.K. and J. Johnson,
glabratus in Georgia’s costal
forests. Georgia Forestry Commission
Pest Alert, October 31, 2005.
Foltz, J.L., A.E. Mayfield
III, J.M. Eickwort, and J.
Leavengood 2006. Redbay
wilt and redbay ambrosia beetle
discovered in northeast Florida.
Poster presented at the North
American Forest Insect Work
Conference, May 22-26, 2006,
Fraedrich, S.W. 2005.
Association of Xyleborus
glabratus and an Ophiostoma
sp. with mortality of red bay (Persea
borbonia) in Georgia and South
Carolina. Poster presented at the
American Phytopathological Society
Annual Meeting, July 30 - August 3,
2005, Austin Texas.
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Rabaglia, A.E. Mayfield III, J.L.
Hanula, J.M. Eickwort, and D.R.
Miller. 2008. A fungal
symbiont of the redbay ambrosia
beetle causes a lethal wilt in
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Haack, R.A. 2003.
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III, S.W. Fraedrich, and R.J.
Rabaglia. 2008. Biology and
Host Associations of Redbay Ambrosia
Beetle (Coleoptera: Curculionidae:
Scolytinae), Exotic Vector of Laurel
Wilt Killing Redbay Trees in the
Southeastern United States. J. Econ.
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Mayfield, A.E. III, J.A.
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2008a. First report of
laurel wilt disease caused by
Raffaelea sp. on Avocado in Florida.
Plant Disease 92 (6): 976.
Mayfield, A.E. III, J.E.
Peña, J.H. Crane, J.A. Smith, C.L.
Branch, E.D. Ottoson, and M. Hughes.
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redbay ambrosia beetle (Coleoptera:
Curculionidae: Scolytinae) to bore
into young avocado (Lauraceae)
plants and transmit the laurel wilt
pathogen (Raffaelea sp.).
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Barnard, J.A. Smith, S.C. Bernick,
J.M. Eickwort, and T.J. Dreaden.
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propiconazole on laurel wilt disease
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the pathogen in vitro. Arboriculture
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Rabaglia, R. 2005.
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