Forest Insect and Disease Leaflet 1 - USDA Forest Service
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Forest Service
U.S. DEPARTMENT OF AGRICULTURE
State & Private Forestry | FS–1192 | February 2022
Forest Insect
and Disease
Leaflet 1
Western Pine Beetle
Introduction height [DBH]) but will attack and kill
The western pine beetle, Dendroctonus trees of most ages and sizes during
brevicomis LeConte (Coleoptera: outbreaks. Rarely is slash or other logging
Curculionidae, Scolytinae), is a bark debris colonized. The beetle may cause
beetle native to parts of western North mortality of 60 to 90 percent of host trees
America. The beetle colonizes and kills in some landscapes (fig. 1). The most
ponderosa (Pinus ponderosa) and Coulter recent notable outbreak occurred in the
(P. coulteri) pines. central and southern Sierra Nevada
Range in California from 2014 to 2017,
Western pine beetle prefers to colonize causing mortality of millions of
larger diameter trees (>20 inches [50 ponderosa pines. This outbreak, as with
centimeters (cm)] diameter at breast
Figure 1. Ponderosa pine mortality caused by western pine beetle. Photos by Christopher Fettig,
USDA Forest Service.
many other outbreaks of western pine During outbreaks, western pine beetle
beetle, was incited by drought and can cause significant economic losses.
supported by landscapes of high-density Dense stands of ponderosa pine 8
host trees. The frequency and severity of to 20 inches (20 to 50 cm) DBH are
droughts are expected to increase likely highly susceptible to colonization. Tree
influencing the frequency and severity of mortality resulting from outbreaks in
future western pine beetle outbreaks. recreational sites and in the wildland
Western pine beetle serves important urban interface is undesirable given
roles in its native habitat influencing the concerns regarding hazard trees, fire risk,
structure, composition, and function and protection of critical infrastructure.
of forests. The beetle often causes tree Western pine beetle occurs from
mortality in forests that are overly British Columbia southward through
dense, over-mature, or both. Trees that Washington, Oregon, Nevada, and
are diseased or weakened by drought, California; eastward to Montana, Idaho,
fire, lightning, or mechanical injuries Utah, Colorado, Arizona, New Mexico,
are more susceptible to attack. Killing and West Texas; and southward into
of weakened trees is an important northern Mexico (fig. 2). Recent work
ecosystem function fulfilled by the beetle suggests populations in Nevada, Utah,
during endemic (low) populations. Colorado, Arizona, New Mexico, Texas,
Figure 2. Distribution
of western pine beetle
(Dendroctonus brevicomis)
with a dashed line indicating
the potential separation of D.
brevicomis (west of line) and
D. barberi (east of line). The
distribution of western pine
beetle in northeastern Mexico
is not well resolved. Map by
Ross Gerrard, USDA Forest
Service.
2
and Mexico may be Dendroctonus
barberi Hopkins based on differences
in morphological characteristics and
other evidence. However, this split would
have few management implications,
and the authors consider these species
to be the same species for purposes of
this publication. Of note, little has been
published on D. barberi. Outbreaks of
western pine beetle tend to be most
severe in California and Oregon. The
beetle is most commonly found at
elevations of 2,000 to 6,000 feet (600 to
1,800 meters [m]).
Evidence of Attack
and Infestation
Attacks are most easily identified by the Figure 3. Pitch tubes of successful western
presence of pitch tubes, masses of resin pine beetle attack (red circles); pitch tubes are
that often contain boring dust. Pitch creamy white with red boring dust within the
pitch tube and in the fissures of the bark. Photo
tubes accumulate at entrance holes on the
by Leif Mortenson, USDA Forest Service.
outer surface of the bark in response to
wounding of the tree when females bore “pitched out” (fig. 4). The presence of
into the tree. Pitch tubes range from predominately white pitch tubes or
creamy white to brownish red in color large streams of resin and the absence of
and are approximately ¼ to ½ inch (6 to boring dust on the bark suggest the tree
12 millimeters [mm]) in diameter (fig. 3). may survive the attack.
Occasionally, only boring dust will be Initial attacks typically occur midway up
present on the outer bark. This is most the tree bole with later attacks occurring
commonly observed during a severe above and below. The beetle requires
drought when a pine’s ability to produce thick bark to complete its life cycle, so it
resin is impaired. In these instances, the rarely attacks trees
Figure 4. “Pitched out”
western beetle after an
unsuccessful attack. Photo
by Christopher Fettig, USDA
Forest Service.
the tree) when attacks surround the beetle emergence generally occurs when
circumference of the bole; and (2) by needles initially turn red. If needles have
blue-stain fungi, Ophiostoma minus, completely faded and dropped, the tree
carried by western pine beetle which no longer contains western pine beetle
likely have deleterious effects on the host
tree, such as limiting water transport
within the xylem (fig. 5). However, it is
not well understood how blue-stain fungi
influence tree mortality.
After a mass attack (i.e., adequate
numbers of beetles must attack the tree
and overcome its defenses), the foliage
begins to change color within weeks to
months. These changes occur more
rapidly during hot and dry conditions.
Initially, the needles fade to a light yellow
green and then to red or reddish brown
eventually falling to the forest floor. The
amount of time it takes for needles to
fade and then fall off a tree varies
depending on the time of year when
beetle attacks occurred, the vigor of the
tree, and other factors. Trees attacked in
late summer and early fall by the Figure 5. Blue-stained wood caused by
Ophiostoma minus, a fungus associated with
overwintering western pine beetle
western pine beetle. Photo by Christopher
generation usually will not fade until Fettig, USDA Forest Service.
spring the following year. Maximum
4
brood. Crown fade due to colonization of fungal associates in their mycangia, a
the tree by western pine beetle will specialized exoskeletal structure. These
occasionally first occur at the midbole, fungi grow within galleries providing
but often the entire crown will fade nutrients to developing larvae.
uniformly. Woodpeckers often target trees colonized
Western pine beetle is able to inoculate by western pine beetle to feed on western
host trees with various microorganisms pine beetle larvae, pupae, and adults.
including O. minus. The fungus appears When searching for prey, woodpeckers
as blue staining of the sapwood (fig. 5) make holes in the bark to feed in the
and as black patches beneath the bark inner bark or chip (flake) away large
(fig. 6). The beetle carries the fungal portions of the bark to feed in the outer
spores on its body and the spores are bark (fig. 7). Among the major tree-
dislodged as the beetle chews through the killing bark beetle species, migration of
bark and phloem. Ophiostoma minus larvae to the outer bark is unique to
grows within tree tissues but any benefit western pine beetle. As such, chipping
to the beetle is unclear. Western pine (flaking) of bark by woodpeckers can
beetle also carries the spores of other often be used to distinguish pines killed
Figure 6. Galleries of western pine beetle; Figure 7. Bark removed by woodpeckers
black patches are caused by Ophiostoma feeding on western pine beetles in late larval,
minus carried by western pine beetle. Photo by pupal, and newly molted (teneral) adult life
Leif Mortenson, USDA Forest Service. stages. Photo by Christopher Fettig, USDA
Forest Service.
5
by western pine beetle from some life cycles. The beetle’s life cycle may
distance. Following bark sloughing or take 2 to 10 months to complete. All
bark removal, the winding S-shaped life stages may be found overwintering
galleries of western pine beetle are due to the overlapping generations.
unique to this species (fig. 6). Western However, larvae are the most common
pine beetle may also co-occur in the life stage to overwinter. The generation
same host tree with other bark beetle time (voltinism) is dependent largely
species such as red turpentine beetle on temperature. In the northern part
(Dendroctonus valens), mountain pine of its range and at higher elevations,
beetle (Dendroctonus ponderosae), and western pine beetle generally has two
Ips spp., among others. generations per year with peak flight
periods occurring in June and late
Life History and Identification
August. However, voltinism increases
Most of the western pine beetle’s life cycle in the southern part of its range and
occurs beneath the bark except when at lower elevations where three to four
adults disperse in search of host trees. generations may occur per year. Attacks
Individuals pass through four occur as early as March and as late as
developmental stages: egg, larva (fig. 8a), December in parts of the range.
pupa (fig. 8b), and adult (fig. 8c).
Temperatures associated with flight
Western pine beetle may have one to initiation and flight cessation vary.
four generations per year. Parent females However, flight initiation tends to occur
may produce one to two generations when daily maximum temperatures
in a season, resulting in overlapping frequently exceed 60° F (15° C) and
A B
Figure 8. Western pine beetle life stages:
C larva (A), pupa (B), and adult (C). Photo (A) by
Mark McGregor, USDA Forest Service; photo
(B) by Donald Owen, California Department of
Forestry and Fire Protection; photo (C) by Erich
Vallery, USDA Forest Service.
6
tend to cease when the maximum hatch occurs, larvae feed on the phloem
daily temperature is below 60° F. After for 10 to 15 days while excavating small
the flight period has initiated, it may galleries. The larvae then move to the
be abruptly interrupted if there is a outer bark where they complete their
substantial drop in average temperature. development. Larvae go through four
Flight occurs during the day and there stages (instars) before pupation. Newly
are two diurnal peaks in flight (in formed (teneral) adults feed in the
California): midmorning and the last 2 to middle and outer bark where O. minus
3 hours of daylight. The multivoltinism spores are encountered and mycangial
of western pine beetle, with more fungi are collected. The mature adult
generations in warmer climates, suggests beetles then emerge from the tree to
climate change may influence future begin another generation.
population dynamics.
Factors Affecting Outbreaks
Female western pine beetles initiate host For a western pine beetle outbreak to
colonization and release aggregation develop, there must be susceptible host
pheromones attracting males and other trees present and suitable weather (e.g.,
females, which may incite mass attack. warm and dry) conducive to beetle
When mass attack occurs, the beetles are population growth.
often able to overcome the tree’s defenses
(pitch production, among others), which Weather
eventually leads to tree death. Males Weather has both direct and indirect
also release aggregation pheromones effects on western pine beetle
and both sexes release anti-aggregation populations. Winter temperatures can
pheromones, which function as “no negatively affect brood development.
vacancy” signs to prevent overcrowding However, temperatures must drop
of the host tree by western pine beetle. below -20° F (-29° C) for several days
Pheromones released from one tree often for significant mortality to occur,
lead to adjacent trees being attacked, which rarely occurs throughout much
resulting in groups of dead trees. of the range of western pine beetle.
Furthermore, due to the thick bark of
When western pine beetles successfully
trees they infest, western pine beetles
attack a tree, they bore through the
are well insulated from lethal cold
bark to the phloem where they mate.
temperatures when overwintering.
The female then bores a winding,
Western pine beetle is vulnerable to
maze-like gallery packed with frass
fluctuations in weather during flight.
laying approximately 60 eggs in small
A sudden storm or significant drop in
niches along the sides of the gallery.
temperature will arrest flight and may
Occasionally, females will reemerge and
lead to beetle mortality. Both events
reattack the same tree or attack another
are common during the spring and
nearby tree. Egg incubation takes 1 to
fall dispersal periods. Indirect effects
2 weeks before hatching. Once larval
are mediated through host trees and
7
community associates. Of note, severe checkered beetles hunting on the bark
drought stress (whether resulting from surface for western pine beetle adults.
elevated temperatures, reductions in Parasitic wasps also commonly attack
precipitation, or both) inhibits tree western pine beetle. Together, predators
defenses, increases susceptibility to mass and parasites may play an important role
attack, and favors western pine beetle in regulating endemic populations but
brood development. are ineffective at suppressing epidemic
Host Tree Susceptibility populations.
For a tree to be successfully colonized Competition
by western pine beetle, an adequate Western pine beetle’s ability to obtain
number of beetles must attack the tree nutrients is most critical during the larva
and overcome its defenses. Western stage. Larvae compete with other larvae
pine beetle generally attacks unhealthy from their brood or with other phloem-
trees with low vigor as healthy pines feeding insects. They are also preyed on
are able to resist western pine beetle by larvae of some predacious insects.
attack by producing enough resin to
either “pitch out” the beetles, or soak the
phloem surrounding the egg galleries
with resin which prevents eggs from
hatching. However, even a healthy pine
can be overwhelmed by large numbers of
western pine beetles.
Predators and Parasites
There are numerous species that prey
on and parasitize western pine beetle.
Woodpeckers are significant predators
of western pine beetle. Temnochila
chlorodia (Coleoptera: Trogossitidae) is
one of the primary invertebrate predators
that is attracted to exo-brevicomin, the
female western pine beetle aggregation
pheromone. Additionally, two checkered
beetles, Enoclerus lecontei and Enoclerus
sphegeus (Coleoptera: Cleridae),
commonly prey on western pine beetle
(fig. 9). Enoclerus lecontei and E. sphegeus
are attracted to ipsdienol, an anti-
aggregation pheromone released by male Figure 9. Enoclerus lecontei (in black circle), an
western pine beetle. A possible early sign important western pine beetle predator. Photo
of attack is the presence of predaceous by Donald Owen, California Department of
Forestry and Fire Protection.
8
Stand and Landscape infestations substantially increases at Characteristics stand densities around 150 ft2 of basal Stand and landscape characteristics are area per acre (34 m2/hectare [ha]) or important factors influencing western a stand density index (SDI, a measure pine beetle outbreaks. Outbreaks are of stocking based on the number of less likely to occur in heterogeneous trees per unit area and DBH of the forests with high tree species diversity tree of average basal area) around 230. and low stocking compared to dense, Susceptible forests in the interior West homogenous forests. Forests with high generally exhibit increased susceptibility stand densities and abundant hosts are at lower stand densities (i.e., around the most susceptible to western pine 120 ft2 of basal area per acre [27 m2/ha]). beetle (fig. 10). Throughout the range of Due to climate change manifesting hotter western pine beetle, host tree density has and drier conditions, however, ponderosa increased greatly over the past century pine forests in general may be more due to fire suppression, historic logging, susceptible today to western pine beetle and other factors. High stand densities at even lower stand densities than their increase competition among trees while historical counterparts. For example, reducing tree growth rates and tree vigor. some recent data suggest stand density They also create beneficial microsite levels
varies with outbreak intensity and stand indicative of short-term tactics designed
and landscape characteristics. Severe to treat current infestations through
outbreaks may result in large amounts manipulating beetle populations with
(i.e., >50 percent) of tree mortality sanitation harvests, chemical applications
but only last 2–3 years due to rapid (i.e., insecticides and pheromones), or
depletion of suitable host trees. Less both. Indirect control involves preventive
severe outbreaks may result in similar measures designed to decrease the
levels of tree mortality accumulated probability and severity of future western
over longer periods. While outbreaks pine beetle infestations by reducing
lower stand density, they also cause shifts tree density, increasing tree vigor, and
in forest structure and composition. encouraging tree species and structural
Forest structure may be greatly altered diversity. Information on the severity and
as average tree size is reduced due extent of western pine beetle infestations
to western pine beetle preferentially necessary to develop management
attacking larger trees. Following strategies requires accurate detection and
outbreaks there are often large increases survey methods. These range from simple
in surface and ground fuels, especially ground-based surveys to aerial detection
after periods of peak snag fall (fig. 11), surveys using digital sketch mapping
which may influence wildfire behavior technology.
and impacts. Insecticides
Management Options Insecticides may be a viable option for
There are two strategies for managing protecting uncolonized individual high-
western pine beetle: direct control value trees in recreational or residential
and indirect control. Direct control is sites. These include contact insecticides
Figure 11. Left: Heavy surface fuel loads about 5 years after a western pine beetle outbreak.
Photo by Crystal Homicz, University of California, Department of Entomology and Nematology.
Right: Snags in an area of heavy ponderosa pine mortality caused by western pine beetle. Photo
by Christopher Fettig, USDA Forest Service.
10applied directly to the tree bole (bole Anti-aggregation pheromones and
sprays) or systemic insecticides injected repellants may be useful to protect
directly into the tree (bole injections) individual trees or small groups of trees.
near the root collar. Several formulations Recent research has demonstrated that
are available and highly effective (90 to verbenone (the beetle’s anti-aggregation
100 percent) when properly applied. pheromone) in combination with
Most provide two field seasons of nonhost volatiles (“Verbenone Plus”)
protection with a single application. If is an effective repellant although not
conditions contributing to outbreaks currently registered for operational use.
do not change, preventative insecticide Verbenone as a stand-alone repellant is
applications will be required until ineffective for protecting ponderosa pine
western pine beetle populations collapse. from western pine beetle.
Lists of insecticide products registered Silvicultural Practices
for protecting trees from western pine and Sanitation
beetle can be obtained online from State
Western pine beetle impacts can be
regulatory agencies.
mitigated through short- and long-term
Attractants and Repellants silvicultural treatments. Stands with
Commercial western pine beetle lures appropriate spacing among host trees
and baits are available. The lures are provide some resistance to infestation.
composed of the female aggregation Encouraging tree species and size class
pheromone (exo-brevicomin), the male diversity also increases resistance.
aggregation pheromone (frontalin) and Thinning practices that reduce average
myrcene, a volatile emitted by ponderosa stand density tosuggests that substantially lower stand lives and critical infrastructure. Fuel
densities are required to maintain treatments, such as prescribed fire,
adequate levels of resistance in chipping, mastication, and thinning of
contemporary forests due to recent trees, may be necessary in some forests.
increases in host stress (associated with Planting of ponderosa pines, other
climate change) and western pine beetle drought-tolerant trees, or both may be
populations. necessary in areas of heavy tree mortality
Prescribed fire may also be used to that lack adequate seed sources to rely
reduce stand density, or it can be used in on natural regeneration. Restoration
tandem with thinning. However, shortly provides an opportunity to create a more
after prescribed fire, some trees may heterogeneous landscape increasing
be weakened and more susceptible to overall resistance to western pine beetle
western pine beetle attack. Removing duff outbreaks and other disturbances.
and litter around the root collar of large Assistance
(>30 inches [76 cm] DBH) ponderosa Forest landowners can obtain more
pines may reduce burn severity, which information on western pine beetle,
will reduce susceptibility to western treatment options, and technical
pine beetle. assistance concerning the use of
Sanitation treatments that remove or pesticides in the United States from
destroy trees infested by western pine a pest control advisor, their local
beetle may be effective for limiting levels university cooperative extension office,
of tree mortality caused by western pine the county agricultural commissioner’s
beetle at small spatial scales (e.g., several office, or their local U.S. Department
acres) if most of the infested trees are of Agriculture (USDA), Forest Service,
sanitized. It is best to remove infested Forest Health Protection program
trees during the fall or winter before representative (http://www.fs.fed.us/
beetle emergence occurs in spring. foresthealth/). This publication and
Sanitation is ineffective during large-scale other Forest Insect and Disease Leaflets
outbreaks. are available online (https://www.fs.fed.
Restoration us/foresthealth/publications/fidls/
Restoring forests impacted by western index.shtml).
pine beetle requires a flexible approach
with management decisions influenced
by landowner objectives, severity of
tree losses, and the overall condition
and location of the affected area. In
most forests, little or no restoration
may occur. However, in the wildland
urban interface removal of hazard trees
may be important to protect human
12Acknowledgments References
This publication is a revision of “Western Fettig, C.J. 2016. Native bark beetles and
Pine Beetle Forest Insect and Disease wood borers in Mediterranean forests of
Leaflet 1” written by Clarence J. DeMars, California. In: Lieutier, F.; Paine, T.D., eds.
Insects and diseases of Mediterranean
Jr. and Bruce H. Roettgering, 1982. The
forest systems. Switzerland: Springer
authors thank Joel Egan (USDA Forest International Publishing: 499–528.
Service, Forest Health Protection), Joel Chapter 18.
McMillin (USDA Forest Service, Forest
Fettig, C.J. 2019. Socioecological impacts
Health Protection), Leif Mortenson of the western pine beetle outbreak in
(USDA Forest Service, Pacific Southwest southern California: lessons for the future.
Research Station), and Karen Ripley Journal of Forestry, 117: 138–143.
(USDA Forest Service, Forest Health Fettig, C.J.; Egan, J.M.; Delb, H.; Hilszczański,
Protection) for reviewing and providing J.; Kautz, M.; Munson, A.S.; Nowak, J.T.;
input on earlier versions of this Negrón, J.F. 2021. Management strategies
publication. to reduce bark beetle impacts in North
America and Europe under altered forest
Author Credits and climatic conditions. In: Gandhi, K. and
Crystal S. Homicz, Ph.D. Student, Hofstetter, R.W., eds. Bark beetle ecology,
University of California, Department of management and climate change. New
Entomology and Nematology, Davis, CA. York: Elsevier Publishing: 345–394.
Christopher J. Fettig, Research Fettig, C.J.; McKelvey, S.R.; Dabney, C.P.;
Huber, D.P.W.; Lait, C.G.; Fowler, D.L.;
Entomologist, USDA Forest Service,
Borden, J.H. 2012. Efficacy of “Verbenone
Pacific Southwest Research Station,
Plus” for protecting ponderosa pine trees
Davis, CA. and stands from Dendroctonus brevicomis
A. Steven Munson, Entomologist (Coleoptera: Curculionidae) attack in
(retired), USDA Forest Service, Forest British Columbia and California. Journal of
Health Protection, Ogden, UT. Economic Entomology, 105: 1668–1680.
Fettig, C.J.; Mortenson, L.A.; Bulaon, B.M.;
Daniel R. Cluck, Entomologist, USDA
Foulk, P.B. 2019. Tree mortality following
Forest Service, Forest Health Protection,
drought in the central and southern Sierra
Susanville, CA. Nevada, California, U.S. Forest Ecology
and Management, 432: 164–178.
Hayes, C.J.; Fettig, C.J.; Merrill, L.D. 2009.
Evaluation of multiple funnel traps and
stand characteristics for estimating western
pine beetle caused tree mortality. Journal of
Economic Entomology, 102: 2170–2182.
13References (continued) Steele, R.; Williams, R.E.; Weatherby, J. C.;
Huber, D.P.W.; Fettig, C.J.; Borden, J.H. 2021. Reinhardt, E.D.; Hoffman, J.T.; Thier, R.W.
Disruption of coniferophagous bark beetle 1996. Stand hazard rating for central Idaho
(Coleoptera: Curculionidae: Scolytinae) forests. INT-GTR-332. Ogden, UT: U.S.
mass attack using angiosperm nonhost Department of Agriculture, Forest Service,
volatiles: from concept to operational use. Intermountain Research Station, 30 p.
The Canadian Entomologist, 153: 19–35. Stephen, F.M.; Dahlsten, D.L. 1976. The
Miller, J.M.; Keen, F.P. 1960. Biology and arrival sequence of the arthropod
control of the western pine beetle. Misc. complex following attack by Dendroctonus
Publ. 800. U.S. Department of Agriculture, brevicomis (Coleoptera: Scolytidae)
Washington, DC. 381 p. in ponderosa pine. The Canadian
Entomologist, 108: 283–304.
Oliver, William W. 1995. Is self-thinning in
ponderosa pine ruled by Dendroctonus Sullivan, B.T.; Grady, A.M.; Hofstetter, R.W.;
bark beetles?. In: L. G. Eskew, comp. Forest Pureswaran, D.S.; Brownie, C.; Cluck,
health through silviculture: proceedings of D.R.; Coleman, T.W. [et al]. 2021. Evidence
the 1995 National Silviculture Workshop, for semiochemical divergence between
Mescalero, NM, May 8–11, 1995. Gen. sibling bark beetle species: Dendroctonus
Tech. Rep. RM-GTR-267. Fort Collins, CO: brevicomis and Dendroctonus barberi.
U.S. Department of Agriculture, Forest Journal of Chemical Ecology, 47: 10–27.
Service, Rocky Mountain Forest and Range Valerio-Mendoza, O.; Armendáriz-Toledano,
Experiment Station: 213–218. F.; Cuéllar-Rodríguez, G.; Negrón, J.F.;
Pureswaran, D.S.; Hofstetter, R.W.; Sullivan, Zúñiga, G. 2017. The current status of
B.T.; Grady, A.M.; Brownie, C. 2016. the distribution range of the western
Western pine beetle populations in Arizona pine beetle, Dendroctonus brevicomis
and California differ in the composition of (Curculionidae: Scolytinae) in Northern
their aggregation pheromones. Journal of Mexico. Journal of Insect Science, 17: 92.
Chemical Ecology 42: 404–413. Valerio-Mendoza, O.; García-Román, J.;
Six, D.L.; Bracewell, R. 2015. Dendroctonus. Becerril, M.; Armendáriz-Toledano,
In: Vega, F.E. and Hofstetter, R.W., eds., F.; Cuéllar-Rodríguez, G.; Negrón, J.F.;
Bark beetles: Biology and ecology of native Sullivan, B.T.; Zúñiga, G. 2019. Cryptic
and invasive species, London: Academic species discrimination in western pine
Press: 305–350. Chapter 8. beetle, Dendroctonus brevicomis LeConte
(Curculionidae: Scolytinae), based on
Stark, R.W.; Dahlsten, D.L.; Berryman, A.A.
morphological characters and geometric
1970. Studies on the population dynamics
morphometrics. Insects, 10: 377
of the western pine beetle, Dendroctonus
brevicomis LeConte (Coleoptera:
Scolytidae). University of California,
Division of Agricultural Sciences, Berkeley,
CA. 174 p.
14Pesticide Precautionary Statement
This publication reports research involving pesticides. It does not
contain recommendations for their use, nor does it imply that the uses
discussed here have been registered. All uses of pesticides must be
registered by appropriate State and/or Federal agencies before they can
be recommended.
Caution: Pesticides can be injurious to humans, domestic animals,
desirable plants, and fish or other wildlife—if they are not handled or
applied properly. Use all pesticides selectively and carefully. Follow
recommended practices for the disposal of surplus pesticides and pesticide containers.
In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil
rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions
participating in or administering USDA programs are prohibited from discriminating based
on race, color, national origin, religion, sex, gender identity (including gender expression),
sexual orientation, disability, age, marital status, family/parental status, income derived from
a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights
activity, in any program or activity conducted or funded by USDA (not all bases apply to all
programs). Remedies and complaint filing deadlines vary by program or incident.
Persons with disabilities who require alternative means of communication for program
information (e.g., Braille, large print, audiotape, American Sign Language, etc.) should contact
the responsible Agency or USDA’s TARGET Center at (202) 720-2600 (voice and TTY) or
contact USDA through the Federal Relay Service at (800) 877-8339. Additionally, program
information may be made available in languages other than English.
To file a program discrimination complaint, complete the USDA Program Discrimination
Complaint Form, AD-3027, found online at How to File a Program Discrimination Complaint
and at any USDA office or write a letter addressed to USDA and provide in the letter all of
the information requested in the form. To request a copy of the complaint form, call (866)
632-9992. Submit your completed form or letter to USDA by: (1) mail: U.S. Department of
Agriculture, Office of the Assistant Secretary for Civil Rights, 1400 Independence Avenue, SW,
Washington, DC 20250-9410; (2) fax (202) 690-7742; or (3) email: program.intake@usda.gov.
USDA is an equal opportunity provider, employer, and lender.
15The Forest Insect and Disease Leaflet (FIDL) series provides
information about insects and diseases affecting forest trees in the
United States. FIDLs are produced through coordinated efforts of
the USDA Forest Service’s Forest Health Protection staff and its
partners from State forestry, academic, and research organizations.
Learn more at www.fs.fed.us/foresthealth/publications/fidls/index.shtml.You can also read
