Invasive Bark Beetles

Forest Insect

& Disease 

Leaflet 176

U.S. Department of Agriculture • U. S. Forest Service

J.C. Lee1,5, R.A. Haack2, J.F. Negrón3, J.J. Witcosky4, S.J. Seybold5

1

 University of California, Davis, California

2

 USDA Forest Service, Northern Research 

Station, East Lansing, Michigan

3

 USDA Forest Service, Rocky Mountain 

Research Station, Fort Collins, Colorado

4

 USDA Forest Service, Forest Health Management, Lakewood, Colorado

5

 USDA Forest Service, Pacific Southwest 

Research Station, Davis, California

Banded elm bark beetle,

Scolytus schevyrewi Semenov

Redhaired pine bark beetle,

Hylurgus ligniperda (F.)

Mediterranean pine engraver,

Orthotomicus erosus

(Wollaston)

Pine shoot beetle,

Tomicus piniperda (L.)

J.R. LaBonte

Pest & Disease Image Library

Bark beetles (Scolytidae) are 

among the most damaging insects 

in Northern Hemisphere forests, 

killing trees by direct feeding and 

by vectoring fungal pathogens. 

In addition to an already formidable native bark beetle complex, 

the number of exotic scolytids 

in U.S. forests has increased 

rapidly, with 53 known species A.G. Gutierrez

A.G. Gutierrez
2

0

10

20

30

40

50

60

1806 1856 1906 1956 2006

Year

Number of species

established as of June 

2007. Scolytids include 

‘true’ bark beetles that 

breed and feed beneath 

the bark in the phloem 

and outer xylem, as 

well as ambrosia beetles 

that breed in the xylem 

and feed on fungi that 

grow in their galleries. 

Because of their close 

association with wood 

and other plant material, scolytids are moved 

easily and unwittingly to many places through trade. As a consequence, some 

species have become nearly cosmopolitan. Between 1985 and 2000, scolytids 

were intercepted at U.S. ports from imported cargo on 6,825 occasions by the 

United States Department of Agriculture – Animal and Plant Health Inspection 

Service (USDA-APHIS). Scolytids represented about 58% of all insects intercepted in solid wood packing material, most frequently in association with tile, 

marble, machinery, steel parts, ironware, granite, aluminum, and slate. Only 

a small portion of incoming cargo can be inspected, so most cargo containers 

are moved directly and quickly to inland distribution sites without inspection. 

Hence live bark beetles can enter the country undetected.

Special challenges posed by invasive bark beetles include:

1. Potential host affiliations and ultimate geographic distribution are difficult 

to predict in the varied new environments of the U.S.

2. The ecological niches of invasive bark beetles may overlap with native 

bark beetles and other insects. If the invasives are superior competitors, 

they may displace native species or affect relationships among native species and their natural enemies.

3. Invasive bark beetles may also introduce invasive pathogens, or may be efficient vectors of native or already established invasive pathogens, adding 

further obstacles to the health of U.S. tree populations.

4. In the absence of specific natural enemies from their native ranges, populations of invasive bark beetles may be poorly regulated. 

Cumulative number of established invasive

scolytid species in the U.S.
3

Documented Impacts

Severe infestations of banded elm bark beetle

(BEBB) have killed drought-stressed elms in 

Colorado and Wyoming. In 2004, 333 infested 

Siberian elms were removed from Newcastle, 

Wyoming.

The Mediterranean pine engraver (MPE) 

and redhaired pine bark beetle (RPBB) have 

caused economic losses in Monterey pine plantations in the Southern Hemisphere by killing 

drought- and fire-stressed trees.

The pine shoot beetle (PSB) has caused severe 

shoot damage to pines in North 

America. Consecutive years of high 

density populations can reduce tree 

growth or affect the appearance 

of nursery or Christmas trees. A 

federal quarantine imposed in 1992 

regulates transport of pine logs, 

Christmas trees, and nursery stock to 

areas not known to be infested. 

Other economically-important 

exotic bark beetles that are not in 

the U.S. but have the potential to 

establish populations and assume pest 

status include Dendroctonus armandii, Dendroctonus micans, Hylastes ater, Ips duplicatus, Ips sexdentatus, Ips typographus, Pityogenes chalcographus, Scolytus intricatus, 

and Scolytus scolytus (major Eurasian pests); 

Carphoborus minimus, Crypturgus mediterraneus, Hylastes linearis, Hylurgus micklitzi, 

Pityogenes calcaratus, and Tomicus destruens

(associated with MPE in the Mediterranean); 

and Hylastes angustatus (associated with 

RPBB in South Africa). Less prominent and 

even unobtrusive bark beetles from overseas 

are also of concern because they may become 

significant pests once established in the new 

environment afforded by the U.S.

Dead Siberian elm infested 

with BEBB

Feeding damage by MPE under the bark of an 

Italian stone pine

Christmas tree with shoot dieback 

from PSB feeding 
4

Approximate Native Distributions

Introduced Distributions (as of June 2007) 

BEBB- central Asia, northern China, Korea, Mongolia, Russia, Siberia

MPE-central Asia, China, Mediterranean, Middle East

RPBB-Asia minor, central Europe, Mediterranean

PSB-Eurasia including Japan, Korea, Scandinavia

BEBB-U.S.

MPE-Chile, South Africa, Swaziland, and U.S. (California); collected historically but likely not established in England, Finland, and Sweden

RPBB-Australia, Brazil, Chile, Japan, New Zealand, Saint Helena, South 

Africa, Sri Lanka, Swaziland, Uruguay, and U.S. (New York, California)

PSB-Canada, U.S.
5

U.S. Distributions (as of June 2007) 

BEBB-22 states, mostly western and midwestern region

MPE- six Central Valley counties of California, occasionally in coastal areas

RPBB-Lake Ontario region of New York, six southern California counties

PSB-16 eastern and midwestern states (MA, CT, RI quarantined but not infested)

Banded elm bark beetle

Mediterranean pine engraver

Pine shoot beetle

Redhaired pine bark beetle

First Detections

The banded elm bark beetle was first detected in April 2003 in Aurora, 

Colorado, and Ogden, Utah, in baited Lindgren funnel traps placed around 

pallet recycling sites, as part of a USDA Forest Service and APHIS-PPQ Early 

Detection and Rapid Response Pilot Project. Inspection of museum specimens 

confirmed that it was captured earlier; one beetle was collected in 1994 in 

Denver, Colorado. Mediterranean pine engraver was detected in May 2004 

at the Fresno Zoo, Fresno, California, in funnel traps during a survey by the 

California Department of Food and Agriculture (CDFA). Established populations of the redhaired pine bark beetle were first detected in November 2000 

near Rochester, New York while evaluating white pine root decline in a Christmas tree plantation. RPBB was also detected in July 2003 in a flight survey trap 

in Los Angeles, California by CDFA. The pine shoot beetle was discovered 

in July 1992 near Cleveland, Ohio, in a Christmas tree plantation. A museum 

specimen was found from 1991 in Michigan. 
6

Reported Hosts

Elms (Ulmus spp.): American, big fruit, chalked bark, 

English, European white, field, Japanese, rock, Siberian, 

smooth-leaved, winged

Rose (Rosaceae): almond, apricot, cherryno, paradise 

apple, peach, pear, other Prunus spp.no

Other: Oleaster, Russian oliveno (Elaeagnaceae), pea 

shrubno (Fabaceae), weeping willow (Salicaceae)

Pines (Pinus spp.): Aleppo, Austrian, Brutia, Canary 

Island, Caribbean, Chinese hard, Chinese red, Coulter, 

David, eastern whitelab, grey, khasia, Italian stone, 

jacklab, Jeffreylab, loblollylab, lodgepolelab, maritime, Mexican weeping, Monterey, pinyonlab, ponderosalab, redlab, 

Scots, shortleaf, slash, sugarlab, Yunnan

Other: Cedar (Cedrus), Douglas-firlab (Pseudotsuga menziesii), firno (Abies), sprucelab (Picea), tamaracklab (Larix)

Pines (Pinus spp.): Aleppo, Austrian, Brutia, Canary 

Island, eastern white, Italian stone, maritime, Mexican 

weeping, Monterey, Montezuma, Scots, slash

Pines (Pinus spp.): Austrian, eastern white, jack, loblolly, lodgepole, longleaf, red, Scots, shortleaf, slash, 

ponderosa, Virginia (cut logs of southern and western 

pines were tested in PSB-infested plantations in Ohio and 

Michigan)

Other: Spruce (Picea), fir (Abies), Douglas-fir (P. menziesii), and tamarack (Larix) in rare cases

bold - recorded as a host in the field in the U.S.

lab recorded as a host in the laboratory, although not yet observed in the field in the U.S.

no not recorded as a host in the laboratory, but reported as a host in the literature from 

its indigenous distribution.

Banded elm bark beetle 

(BEBB) 

Mediterranean pine engraver (MPE) 

Redhaired pine bark beetle 

(RPBB) 

Pine shoot beetle (PSB) 
7

Areas of Concern Fungal Associations

Populations of BEBB are damaging 

stressed elms in the arid Rocky Mountain 

and Intermountain regions where Siberian 

elm is a primary shade tree. The ultimate 

impact of BEBB on American elm populations across the U.S. is uncertain.

Beetles emerging from diseased American elm logs carried spores of Ophiostoma novo-ulmi, the causative agent 

of Dutch elm disease. Before mating, 

BEBB feeds in twig crotches; this may 

enable beetles to transmit the pathogen 

to living trees.

The broad host range of MPE could facilitate its spread throughout California to 

coastal Monterey pines, native pines in the 

mountain ranges, and to distant warm regions such as the Southeast where loblolly, 

shortleaf, and slash pine are present.

Ophiostoma (Ceratocystis) ips, Leptographium lundbergii, L. serpens, and 

Graphium pseudormiticum have been 

isolated from adults infesting various 

pines overseas. In California, O. ips

was the most frequently isolated fungus 

from beetles infesting cut pine logs.

RPBB may affect Aleppo, Canary Island, 

and Monterey pines frequently grown as 

shade trees in southern California. Its 

potential to vector procera root pathogen 

may affect Christmas tree plantations in 

the East and the unexposed Northwest.

Leptographium lundbergii, L. procerum, 

L. serpens, O. ips, O. galeiformis, and 

Ceratocystiopsis minuta have been isolated from adults and galleries in pines 

overseas. RPBB could vector black 

stain root disease, L. wageneri, a native 

pathogen that already threatens western 

pines.

Throughout the Northeast and Lake States, 

PSB may cause damage in poorly managed Christmas tree or nursery plantations. 

A federal quarantine was enacted to retard 

the southern and western spread of PSB.

PSB vectors Leptographium wingfieldii, 

causing blue-stain of the xylem of Scots 

pines. Beetles and infested trees have 

also been associated with L. lundbergii, 

L. huntii, L. procerum, and Graphium 

sp.
8

Identification

The banded elm bark beetle

generally has a light-to-dark 

band across its wing covers (elytra). It resembles the 

smaller European elm bark 

beetle (EEBB), Scolytus multistriatus, another exotic that 

was established in the U.S. 

a century ago and is a vector 

of Dutch elm disease. The 

two species can be distinguished by size, ventral spine 

placement, presence/absence 

of elytral band, and posteriolateral teeth along the edges 

of the underside. Females 

excavate a single vertical egg 

gallery in the phloem.

The Mediterranean pine engraver is 2-3 mm long, dark 

brown, and has four spines 

on its end (declivity). The 

second spine is largest and 

very pronounced in males. 

It may be confused with the 

native species, Ips pini, whose 

males have a large third spine 

and whose females have four 

equally sized spines. Other 

native species, Orthotomicus 

caelatus and Ips latidens, 

have only three declivital 

spines.

BEBB

EEBB

band

no band

3-4 mm

2-3 mm

no teeth

ventral spine more 

posterior on 2nd

abdominal sternite

Posteriolateral teeth 

on sternites 2-4

ventral spine more 

anterior

MPE male 

Ips pini male

O. caelatus Ips latidens 

Ips pini female

In the nuptial 

chamber, two 

females have 

joined a male 

and excavated 

opposing egg 

galleries.

Drawings Wood 1982

Nuptial 

chamber

A.G. Gutierrez

Vertical egg gallery 

of BBEB

MPE female 

A.G. Gutierrez
9

The redhaired pine bark 

beetle is 5-6 mm long and 

black. RPBB is distinguished 

from PSB by RPBB’s abundant setae (hairs) that point 

in various directions on the 

elytral declivity. Under the 

microscope, numerous reddish or yellowish hairs cover 

the beetle. A native species, 

Hylastes porculus, appears 

similar, but is nearly hairless. 

RPBB has a raised longitudinal tubercle on the frons, the 

front part of the head behind 

the mouthparts.

The pine shoot beetle is 3-5 

mm long and brown to black. 

PSB is distinguished from 

other species of Tomicus by 

its smooth elytral intervals on 

its declivity (arrow). PSB may 

resemble Dendroctonus spp. 

(e.g., southern pine beetle), 

but its antennal stalk (funicle) 

has six short segments rather 

than five/seven as in Dendroctonus. The egg gallery is 

vertical with a bend or hook 

at the end.

Declivity with 

dense, but variable red and 

yellow hairs

Females 

construct 

a long egg 

gallery

UGA 

1669028

W.M. Ciesla S. Passoa

Antennal funicle with segments numbered

Declivity with single 

rows of erect hairs, and 

smooth interval

S. KinelskiPassoa & Cavey 1993

A.G. Gutierrez
10

Life Cycles

Banded elm bark beetle females construct single vertical egg galleries about 

4-6 cm long that lack a nuptial chamber. Males move about the bark surface 

searching for entrance holes and mate with multiple females at these entrances. 

Between 20 and 120 eggs are laid and females guard the egg gallery until 

death. Larvae develop through four or five instars and migrate to the outer bark 

to pupate. There are two to three generations in the U.S. Larvae, pupae, and 

adults overwinter, and the adults start emerging in early spring. 

Mediterranean pine engraver males construct a nuptial chamber and emit 

an aggregation pheromone. Two or three females mate with each male, and 

each female excavates an egg gallery in opposite directions laying 26-75 

eggs. Adults may start a new gallery in another location. In California, MPE 

overwinters as larvae, pupae, and adults beneath the bark; adults fly during 

all months except late December and January; and the beetle has three to four 

generations per year. Newly laid eggs have been observed as early as the first 

week of March and as late as the last week of November.

Redhaired pine bark beetle females 

construct a nuptial chamber, and one 

RPBB male mates with one female. A 

female lays up to 500 eggs in a vertical 

gallery that is sometimes one meter long. 

Galleries are often found on the undersides of logs in contact with moist soil. 

In California, RPBB adults fly all year, 

and the beetle completes two to three 

generations per year.

Pine shoot beetle adults mate and construct single 

vertical egg galleries in dying, cut, or severely 

stressed pines. New adults emerge in early summer 

and feed primarily in current-year shoots during the 

summer. Each beetle can damage one to six shoots. 

PSB completes one generation per year in the 

U.S. Adults overwinter in the bark at the base of 

stems and rarely in the shoot. Overwintering adults 

emerge in early spring when temperatures exceed 

10-12°C (50-54°F).

RPBB adults overwinter beneath the bark

Hollowed-out shoot fed on 

by PSB

J. Cavey
11

Management

Managing invasive bark beetle populations 

begins with prevention tactics, early detection, 

and occasionally quarantine. Semiochemicals, 

which are often based on the beetle’s aggregation 

pheromone or host attractants, are used as lures in 

monitoring traps. Traps are typically cardboard 

flat panel traps, or plastic funnel traps that present 

a dark, cylindrical silhouette to the flying beetles. 

Infested material should be removed and burned, 

debarked, or chipped to prevent build up and 

spread of the populations. Live trees should be 

adequately watered to prevent stress and reduce 

susceptibility to bark beetle attacks. Registered 

insecticides (e.g., carbamates, pyrethroids) are 

available as preventive treatments and should 

be applied before high value trees are attacked. 

Consult your State Department of Agriculture or 

County Extension office for a list of registered 

products.

Funnel trap

Semiochemicals for monitoring invasive bark beetles 

and additional recommendations

BEBB MultilureTM (Pherotech), which was developed for the smaller European elm 

bark beetle, is also moderately attractive to BEBB. 2-Methyl-3-buten-2-ol is 

weakly attractive.

MPE (–)-Ipsdienol, 2-methyl-3-buten-2-ol, and α-pinene in combination are attractive synergistically. 

(+)-Ipsdienol can be used to interrupt MPE flight to otherwise attractive 

materials.

RPBB α-Pinene and ethanol are attractive synergistically. RPBB burrows into 

host material that is in contact with wet soil. Therefore, elevating cut logs 

aboveground can decrease the level of infestation in cut pine logs.

PSB α-Pinene and trans-verbenol are attractive.
12

Support USDA Forest Service-USDA APHIS Early Detection and Rapid 

Response Pilot Project, Special Technology Development Program R2-2004-

2005, USDA NRI CSREES #2006-35302-16611, and UC Exotics/Invasive Pest 

and Diseases Grant #05XU039 

Reviews D.A. Duerr, D.A. Haugen, D.G. McCullough, A.S. Munson, 

I.R. Ragenovich, R.C. Venette, and D.L. Wood

Photo and figure credits C. Bohemia, J. Cavey, W.M. Ciesla, A.G. Gutierrez, 

D.N. Thomas, S. Kinelski, J.R. LaBonte, S. Passoa, and J. Vandewater. Remaining photos were taken by authors.

References 

• Cavey JF, Passoa S, Hoebeke ER. 2002. New Introduction: The red-haired bark beetle, 

Hylurgus ligniperda. Forest Service Pest Alert NA-PR-03-02. 

• Cavey J, Passoa S, Kucera D. 1994. Screening aids for exotic bark beetles in the Northeastern United States. USDA Forest Service NA-TP-11-04.

• Haack RA. 2001. Intercepted Scolytidae at U.S. ports of entry: 1985-2000. Integrated Pest 

Management Reviews 6: 253-282.

• Haack RA. 2006. Exotic bark- and wood-boring Coleoptera in the U.S.: recent establishments and interceptions. Canadian Journal of Forest Research 36: 269-288. 

• Haack RA, Kucera D. 1993. New introduction-Common pine shoot beetle, Tomicus piniperda (L.). USDA Forest Service Pest Alert NA-TP-05-93. 

• Haack RA, Poland TM. 2001. Evolving management strategies for a recently discovered 

exotic forest pest: the pine shoot beetle, Tomicus piniperda. Biological Invasions 3: 307-322.

• Lee JC, Negrón JF, McElwey SJ, Witcosky JJ, Seybold SJ. 2006. Banded elm bark beetleScolytus schevyrewi. USDA Forest Service Pest Alert R2-PR-01-06.

• Lee JC, Smith SL, Seybold SJ. 2005. Mediterranean pine engraver. USDA Forest Service 

Pest Alert R5-PR-016.

• LaBonte JR, Rabaglia RJ, Hoebeke ER. 2003. A screening aid for the identification of the 

banded elm bark beetle, Scolytus schevyrewi Semenov.

• Negrón JF, Witcosky JJ, Cain RJ, LaBonte JR, Duerr II DA, McElwey SJ, Lee JC, Seybold 

SJ. 2005. The banded elm bark beetle: A new threat to elms in North America. American 

Entomologist 51: 84-94.

• Passoa S, Cavey JF. 1993. Key to help screen Tomicus piniperda (L.) from other North 

American Scolytidae. USDA Forest Service NA-TP-06-93.

• Petrice TR, Haack RA, Poland TM. 2004. Evaluation of three trap types and five lures for 

monitoring Hylurgus ligniperda and other local scolytids in New York. Great Lakes Entomologist 37: 1-9. 

• Wood SL. 1982. The bark and ambrosia beetles of North and Central America (Coleoptera: 

Scolytidae), a taxonomic monograph. Great Basin Naturalist Memoirs 6: 1–1359.

Information about pesticides and commercial vendors appears in this publication. Publication of this information does not constitute endorsement or recommendation by the U.S. Department of Agriculture, nor does it imply that all 

uses discussed have been registered. 

USDA is an equal opportunity provider and employer.