Shothole Borer: An Ambrosia
Beetle of Concern for
Orcharding in the Pacific Northwest
H. Omroa Bhagwandin, Jr.
Northwest Chestnuts, 183 Shady Grove, Onalaska, WA 98570
published in the 93rd Annual Report of the Northern Nut
Growers’ Assn., p. 168-177,
and published here with permission of the
Bhagwandin, H.O. 1992.
The Shothole Borer: An
Ambrosia Beetle of Concern for Chestnut Orcharding in the Pacific
The shothole borer of chestnuts, Xyleborus dispar (F.) (Coleoptera:
Scolytidae), is a serious pest of young chestnut trees throughout
the Western Cascades and may now be the limiting factor in successful
orchard establishment. It
is increasingly more ubiquitous in forested areas where it utilizes
evidently all broadleaf tree species in its range.
Having an average of two generations per year, adult borers
tunnel into host sapwood tissue for colonization.
Mass attacks on hosts contribute to the ultimate demise of
seemingly healthy trees. A
literature review was done to determine the extent of knowledge reported
on this beetle and to gain a better understanding of how to effectively
prevent and/or control infestations in new or existing orchards.
The shot hole borer[i], Xyleborus dispar (F.) (Coleoptera:
Scolytidae), is a European ambrosia beetle that was most likely
introduced into the U.S. several years prior to 1816, (59) but was first
officially reported by Peck in the Massachusetts Agricultural Journal in
1817 as Anisandrus pryi. It
was found in the Northwest in Clarke County, Washington in 1901 and first
reported as utilizing chestnut as a host species in the Northwest as early
as 1912 (59). Shothole borer was reported in British Columbia in the early
1920’s (28, 33) and was recorded in California as attacking a variety or
deciduous trees in 1942 (31).
Shothole borer has now been
found to be a pest throughout the northwestern states and western Canada
(6). New chestnut plantings
are extremely susceptible to attack by this beetle, representing a
critical factor in successful orchard establishment. The purpose of this paper is to highlight important
observations and conclusions made by previous research on ambrosia and
bark beetles in order to gain a better understanding of how to effectively
prevent and/or control infestations of Xyleborus dispar in new and
existing chestnut orchards.
As an insect pest, the bark and timber beetles, Scolytidae,
have been extensively studied due to their significant economic
destructive capabilities in both forest and agro ecosystems.
The original description of Xyleborus dispar was done in
1792 by Fabricius who most likely gave it the species name based on the
disparity between the two sexes. There
have been four noteworthy attempts to classify the Scolytidae in North and
Central America (4, 9, 54, 60). The
most recent taxonomic monograph puts the shothole borer in the genus Xyloborus
of the tribe Xyloborini and establishes genus synonymy with Anisandrus,
Anaeretus and possibly Cyclorhipidion (60).
2.8-3.7 mm, twice as long as wide; Color dark brown to black; Elytra
roughly 62.5% of total length, 1.3x longer than wide, striated
longitudinally parallel, interstrial space shining, smooth.
Length 1.5-2.1 mm; dwarfed, thorax disk and elytra strongly convex;
Egg: Length 1mm by 0.06 mm diameter; oblong or oval and clear to
white in color.
Larvae: Length 5mm x 1.45 mm at widest part, white, grublike,
legless; slightly sclerotized heads with brown mouth parts; Three instars
Pupae: Length 4mm x 1.5mm at widest part; Color white.
Males easily distinguishable by their small size relative to
females (16, 59).
The shothole borer, Xyleborus dispar, is within an
ecological group of the Scolytidae known as the ambrosia beetles.
Ambrosia beetles are characterized by their utilization of the
sapwood of physiologically stressed and recently dead trees for
colonization and by the use of symbiotic fungi as their sole food source. Xyleborus dispar forms an ectosymbiotic relationship
with the fungus Ambrosiella hartigii Batra (Fingi Imperfectii)
which they transport into the host tree in specialized glands and
cultivate on the tunnel walls of their galleries (3, 19, 48).
When growing in the galleries of the host trees, the mycelial form
of the fungus converts to a yeast like derivative in response to borer
excrements and continued cropping (3, 21, 27, 41).
This yeast like form of the fungus is what is known as ambrosia.
Scolytidae beetles are the primary invaders in dying plant material
and thus function as vectors of the decay process in forest ecology.
After the insect has moved on in search of a new host the fungus
remains and accelerates the breakdown and degradation of the host tree.
The life cycle of X. dispar is described in several
papers (7, 9, 16, 20, 29, 52, 59, 60).
The one distinct feature, which separates it from all the other
bark and timber beetles, is that it is the only species in the Scolytidae
to exhibit a true diapause (60). Adult
beetles overwinter within the sapwood tunnels they excavate in the limbs
and trunks of infested trees. Males
are flightless and spend their entire lives within the galleries or near
tunnel entrances where mating occurs.
Female emergence is timed with the beginning months of spring. Once
the female has made contact with a suitable host, she crawls around on the
trunk searching for a site to begin boring an entrance hole.
The entrance hole is about the diameter of a pencil lead and in
small trunks and branches is usually found at the base of leaf and bud
Immediately after tunneling into
the xylem, fungal gardens are inoculated by the female and a small clutch
of eggs is laid. Clutch size
is reported as varying in number being between 1-10 eggs for the primary
clutch and up to 45 eggs for subsequent clutches. Eggs are typically laid at the end of main or lateral
galleries and take from two to three weeks to hatch (59). Larvae take about four weeks for full development and do not
contribute to gallery excavation, but rather, move freely about while
feeding upon the ambrosia. The
pupal stage lasts another four weeks, making the total life cycle from egg
to adult about 10-11 weeks (59). Tunnels
are continually expanded by the parents as the brood size increases or
until the moisture content of the host deteriorates.
Host moisture must be available in the tunnels to be able to
support the growth of the ambrosia. Adult
females will leave the colony to find new hosts or will re-work an
Brood development is a
temperature dependent function with development time being proportional to
development time from larval to adult was accelerated by 52% when
temperature was maintained at a constant 21 C (69.8 F) versus a constant
13 C (55.4 F) (1). Cool
temperature appears to impede the growth of newly hatched larvae.
Current flight period and patterns of flight are also influenced by
the success of the beetle developmental period of the previous year.
If the previous season was warm it would have been conducive to the
accelerated development of the brood and conceivably more fully developed
adults will be ready to emerge after the seasonal diapause the following
spring (34). Typically there
are two generations per year in Oregon (9).
Signs of early spring attack
include a wilting of newly emerged bud growth and frass tailings from
borer excavations. Frass will
usually be evident on infected limbs and alongside, or at the base of
trunks. In late summer
galleries usually become considerably honeycombed throughout an infection
site to such an extent that trunks or branches become weakened and
brittle, breaking easily when bent over, thereby exposing numerous larvae
The host trees in association with X. dispar include
potentially all deciduous fruit and forest trees in its range (6, 59).
Those that have been reported include Acer, Aesculus, Alnus,
Betula, Castanea, Crataegus, Corylus, Cydonia, Fagus, Fraxinus, Juglans,
Leriodendron, Malus, Platanus, Populus, Prunus, Punica, Pyrus, Quercus,
Salix, Vitis (6, 9, 16, 17, 31, 60).
In addition, Xyleborus sp. are reported throughout the world
as pests of Carya (22), Camillia (8, 15, 37, 51), Cocos (32)
and yam tubers (58).
The condition of the host tree
is a major factor in susceptibility to attack.
It has been consistently reported by several sources (25, 30, 35,
43, 45, 46, 56) that ambrosia beetle attacks are limited primarily to
hosts that are physiologically compromised due to some recent injury or
stress. Under epidemic or
outbreak proportions, these borers will attack perfectly healthy trees
found in the vicinity of suitable hosts – if preferred host material is
of limited availability.
SELECTION AND FLIGHT RESPONSE
Olfaction is the dominant response factor in flight orientation
to a suitable host (23, 24, 25). Field
observations (10, 23, 34, 43) indicate that ambrosia beetles are
stimulated to fly upwind and in the direction of the source in response to
odor attractions. In the
absence of olfactory stimulus, pioneering beetles are distributed
uniformly throughout the stand (45).
Beetles are guided to a chemical stimulus by a type of klinokinesis,
(47, 61) in which the attractant source is located by positive orientation
to successive pulses from a volatile cloud within its atmospheric range.
There are two phases of
olfactory-guided dispersal: primary
attraction (allocation) and secondary attraction (concentration) (24).
Primary attraction involves the pioneering flight of adult be3etles
accurately pinpointing a specific target host within a given stand (7, 10,
11, 18, 46). The pioneer
flight in X. dispar is done by the female since males lack the
ability to fly. The chemical
stimuli in this stage of olfactory guidance are volatile breakdown
products of anaerobic host tissue metabolism (7, 26), the main component
of which is ethanol (7, 36, 52). Single
trees are selected in this early phase of attack based on their current
physiological state, with host stress being positively correlated with the
production of ethanol.
An important factor in a
host’s resistance to the primary phase of infection in conifers is
oleoresin exudation pressure, (OEP), which is directly related to water
stress (45). Low epithelial
cell turgor pressure in resin duct lining results in decreased flow in
response to a disturbance. If
a beetle encounters heavy resin flow in a pioneer tunnel it will be
mechanically flooded out and/or chemically repelled rendering the borer
attack effectively unsuccessful (40, 45, 55).
In the coastal Pacific Northwest there is typically no critical
soil moisture deficiency that negatively affects the OEP during the early
season flight of ambrosia beetles (45).
This is not necessarily true of the summer flight.
Should a primary attack be
successful, species-specific attractant pheromones will then be produced
by the pioneering female (7, 12, 40, 45, 47).
This initiates the concentration phase of olfactory-guided flight.
Attractant pheromones have been isolated from the alimentary system
(39, 56) and frass of pioneering female beetles (47).
The intensity of secondary attractant is dependent on the
concentration of pioneering beetle’s host infestation (47) and/or
entirely on the condition of the host (7, 56).
A synergistic influence, associated possibly with ethanol, has been
suggest4ed as being responsible for increasing the activity of this insect
produced attractant pheromone (7). Host
logs not undergoing active anaerobic metabolism, experimentally baited
with pioneer beetles, produced no attraction (7).
The secondary attractant
pheromone is a far stronger olfactory guide relative to primary
attractants. It stimulates female beetles to converge en masse upon
a host and begin colonization, following a primary attack.
Some species of ambrosia beetles will mass aggregate on vertical
objects near established sources of attraction without any apparent regard
for the suitability of the object as host material (45).
This suggests that visual orientation aids olfactory guidance (20).
It ahs been shown in field studies with ambrosia beetles that
response to secondary attraction can occur within four hours (43).
There are distinct seasonal and diurnal response patterns to
secondary attractants and these patterns are influenced by temperature,
light and wind speed (7, 18, 47, 48).
Differences in the capacity of flight response to attractant
stimuli between individuals and populations within a brood have been shown
to be based on the physiological condition of the beetles rather than due
to inherited ability (23). A
very thorough study (49) on the effects of temperature upon the various
activities of the Douglas fir beetle, Dendroctonus pseudotsugae
(H.) emphasizes temperature as the most important of several environmental
factors that influence a given beetle activity.
It has been shown that ambient temperature determines mode of
action once the threshold temperature for that action has been reached.
Absolute limits of activity were
laboratory tested (49) and found to be between 0-1 C (32-33.8 F), where
there is a reaction to contact or light; and 49 C (120.2 F), when thermal
death occurs. Heat injury
resulted in temperatures over 38-39 C (100.4-102.2 F).
At temperatures over 10 C (50 F) beetles exhibited relatively high
boring ability. An increase
in temperature elicited increased boring activity correspondingly.
At higher ambient temperatures beetles are able to bore throughout
thicker bark in relatively shorter time periods.
Activity response showed a
6-hour lag when plotted against daily temperatures due to the insulative
effective of the host. Thus,
boring activity was greatest in late evening to midnight, with the least
activity occurring in the mornings. Flight
activity occurred between a threshold of 10 C (540 F); to the maximum
reported flight temperature of 32 C (89.6 F) depending on the species, its
population density and the availability of sources of attraction (24, 34,
43, 48). Ambrosia beetles
will fly at cooler temperatures in the presence of sunlight (48). Spring peak flights occurred at midday with flight ceasing
one hour before sunset (47). No
flight occurred in Trypodendron lineatum at night, at temperatures
above 29.7 C (86 F), or at heights above 6 ft. when wind velocities exceed
3 m.p.h. (47). Directed
flight from low light to high light intensities was noted and implications
for flight from shaded forests to clear cut areas were mentioned (48).
Relative humidity increased the
tolerance and survivability in test beetles (49).
Since relative humidity is effectively 100% inside beetle
galleries, only temperatures above 43 C (109 F) are considered injurious.
Surface temperatures on logs exposed to solar radiation for an
afternoon commonly reach these temperatures.
This may explain a preference in beetles for attack concentrations
on the cooler surface areas of hosts such as underneath a branch node or
on the shaded side of a branch or trunk.
It is important to note that
there are two distinct seasonal flights in the Pacific Northwest:
an early spring flight and an August summer flight.
The summer flight coincides with decreased soil moisture when hosts
are potentially more drought stressed (45).
Summer flight ability is enhanced by temperatures between 25-32 C
(77-89.6 F) (49). There are
two daily summer peaks: one
before and one after noon (47). These
peaks can be determined by monitoring local microclimatic data.
Flight distances of bark beetles
were reported up to 5000-1000m (10-3000 ft) (23).
Flight mill lab tests showed that beetles were physiologically
capable of flight for up to 11.27 km (7 mi) in four hours.
This can amount to 24-32 km (15-20 mi) per day for several days in
still air with healthy Douglas-fir beetles, D. pseudotsugae.
This implies the virtual impossibility of controlling population
outbreaks by silvicultural methods (1).
Relative velocity was recorded to be 115 m/min (4.29 mph) in D.
Castanea spp. Seems to be a preferred host of X. dispar
in the Pacific Northwest. Apparently
healthy chestnut trees showing no obvious signs of stress are often
attacked. Upon more thorough
examination it can often be shown that some of these trees may actually be
under duress due to one or several factors including:
transplant shock, winter freeze or sunburn, high water table, poor
soil, mechanical injury, graft incompatibility, or some other disease or
insect infestation. The
vascular system of Castanea is ring porous, characterized by large
diameter vessels, which seal themselves off in response to injury.
This walling off of portions of the vasculature system can result
in cambial dieback due to a girdling effect.
This phenomenon may be responsible for rendering thin barked trunks
and limbs in chestnut relatively more susceptible to injury than other
hosts under similar environmental influences.
As chestnut bark thickens and becomes more woody, increased
resistance to border attack may be affected.
Positive correlations have been
made between epidemic outbreaks and periods of rainfall deficiency,
catastrophic winds, snows, floods and fires (13, 30, 53).
Differences in length of dispersal (primary fight phase) and the
distance beetles will fly to an attractant source have been reported
during normal and epidemic population conditions (24).
Under normal conditions pioneer beetles will fly long periods and
cover long distances in search of a suitable host.
Under epidemic outbreaks, beetle populations explode into the
surrounding hosts in the immediate vicinity without regard for their
suitability as compatible hosts. In
mass aggregation like this, beetle populations can overcome even healthy
The Pacific Northwest has been
experiencing reduced rainfall and increased snow pack deficiencies since
1986. In addition, timber
clearcutting has reached record levels over this same time period. The
combined effect has had significant impacts on the overall health of host
ecosystems. Such a cycle
would encourage populations levels of X. dispar due to decreased
host resistance to borer attacks and may contribute to some of the
problems currently experienced with young chestnut orchard establishment.
Based on this literature review, some control methods are offered
as suggestions for combating the shothole borer in potential and existing
chestnut orchard blocks. Prevention
is by far the best control, but may be impractical given the limits of
control on natural climatic cycles and the proximity of uncontrollable
attractant sources to an already established orchard.
When possible, considerations for the location of a potential
chestnut orchard should take into account both the health and relative
proximity of potential beetle attractant sources adjacent to a proposed
orchard site. Avoid planting
near unhealthy forests or abandoned orchards and recent clear cuts.
Orientation of the orchard should be with respect to prevailing
winds and sources of primary and secondary attractant volatiles.
Cultural practices should begin
with the monitoring of orchards for determination of seasonal flight
periods and time of day at which peak flight occurs on a given site.
An understanding of borer reproduction cycles will enhance the
ability to predict beetle activity and can contribute to some of the
controlling factors affecting potential host stress.
One of the most important potential controllable factors available
to the orchardist for influencing host resistance to borer attack may be
to increase cell turgor pressure. High
plant cell turgor pressure can be obtained by maintaining adequate soil
moisture in the orchard during peak flight periods.
Another controllable factor is the limiting of point source primary
attractants within the orchard. Non-compatible
graft unions, nutritionally or otherwise stressed trees and bark damage
caused by winter freezing or sun scalding can initiate cambial
fermentation and often become some of the most common point sources of
primary attractants in chestnut orchards.
Judicious thinning of these and all other non-vigorous and
unhealthy growth in the orchard should be done and, along with any
Suggestions for future research
include the development of resistant cultivars (8, 42), the use of ethanol
based (26, 36, 38), and/or pheromone confusion traps (25, 39, 43, 44, 56),
the introduction of predator control organisms (14) and the development of
biological pesticides (5, 50, 57). Research also needs to be done to d3eterine proper trap
placement for effective control. A
concern with the use of attractant-chemical traps for control of X.
dispar is the possibility of inducing epidemic proportion responses
within the orchard.
Atkins, M.D. 1961. A
study of the flight of the Douglas-fir beetle, Dendroctonus
pseudotsugae Hopkins (Coleoptera:
Flight capacity. Can.
Atkins, M.D. 1967. The
effect of rearing temperature on the size and fat content of the
Douglas-fir beetle. Can. Ent.
Batra, L.R. 1967. Ambrosia
fungi: A taxonomic revision
and nutritional studies of some species. Mycologia 59: 976-1017.
Blandford, W.F.H. 1895-1907. Fam.
Scolytidae in Biologia Centrali-Americana, 4(6): 81-298.
(From Bright, 1968).
Bridges, J.R. and D.M. Norris 1977. Inhibition of reproduction of Xyleborus ferrugineus by
ascorbic acid and related chemicals J.
Ins. Physio. 23(4): 497-501.
Bright, D.E., Jr. 1968. Review
of the tribe Xyleborini in America north of Mexica (Coleoptera: Scolytidae).
The Can. Ent. 100: 1289-1323.
Cade, S.C. 1970. The
host selection behavior of Gnathotrichus
sulcatus Leconte (Coleoptera:
Ph.D. thesis, College of Forest Resources University of Washington, 112p.
D. 1972. Differences in susceptibility of tea clones in Ceylon to
the shot-hole borer beetle, Xyleborus fornicatus (Eichh.) (Coleoptera:
Scolytidae). Z. Agnew. Ent. 68(3): 300-07.
Chamberlin, W.J. 1939.
The Bard and Timber Beetles of North America.
Ore. State Coop Assoc., Corvallis, 470 pp.
Chapman, J.A. 1962.
Field studies on attack flight and log selection by the ambrosia
beetle Trypodendron lineatum (Oliv.) (Coleoptera:
Scolytidae), Can. Ent. 94: 74-92.
Chapman, J.A. 1963. Field
selection of different log odours by scolytid beetles.
Can. Ent. 95: 673-6.
Chapman, J.A. 1966. The
effect of attack by the ambrosia beetle Trypodendron
lineatum (Oliv.) on log attractiveness, Can. Ent. 98:
Craighead, F.C. 1925. Bark-beetle
epidemics and rainfall deficiency, J. of Econ. Ent. 18:
Danthanarayana, W. 1968.
Outbreaks of caterpillar pests as limiting factors in controlling
shot-hole borer, Xyleborus fornicarus (Eichh.) (Coleoptera:
Scolytidae) of tea in Ceylon.
In International Congress of Entomology, 13th, Moscow,
Trudy 2: 319-20.
Danthanarayana, W. 1973.
Host plant-pest relationships of the shot-hole borer of tea, Xyleborus fornicatus, (Coleoptera:
Scolytidae). Ent. Exp.
Appl. 16(3): 305-12.
Doane, R.W., E.C. Van Dyke, W.J. Chamberlin and H.E. Burke
1936. Forest Insects.
McGraw-Hill Book Co., Inc. New York and London.
Essig, E.O. 1926. Insects
of Western North America. MacMillan,
NY, pp. 510-13, 520-21.
Francia, F.C. and K. Graham 1967. Aspects orientation behavior in the ambrosia beetle Trypodendron
lineatum (Olivier). Can.
J. of Zoo. 45: 985-1002.
Francke-Grossman, H. 1967.
Ecrosymbiosis in Wood Inhabiting Insects.
In: Henry, S.M. (ed.),
Symbiosis. New York:
Academic Press, Vol. II, pp. 141-205.
French, J.R.J. 1972. Biological
Interrelationships between the ambrosia beetle Xyleborus
dispar and its symbiotic fungus Ambrosiaella hartigii.
Unpublished Ph. D. Thesis, Dept. of Ent., Oregon State University,
French, J.R.J. and R.A. Roeper 1972.
In vitro culture of the ambrosia beetle Xyleborus
dispar (Coleoptera: Scolytidae)
with its symbiotic fungus, Ambrosiella
hartgii. Ent. Soc. Amer.
Gagne, J.A. and W. H. Kearby 1979. Life history, development and insect-host relationships of Xyleborus
celsus (Coleoptera: Scolytidae)
In Missouri Pest of black hickory, Carya texana.
Can. Ent. 111(3): 295-304.
Gara, R.I. 1963.
Studies on the flight behavior of Ips
confuses (Lec.) (Coleoptera: Scolytidae)
in response to attractive material. Contrib.
Boyce Thompson Inst. 22: 51-66.
Gara, R. I. And J. P. Vite 1962. Studies on the flight patterns of bark beetles (Coleoptera:
Scolytidae) in second growth ponderosa pine forests.
Contrib. Boyce Thompson Inst. 21:
Gara, R. I., J. P. and H. H. Cramer 1965.
Manipultions of Dendroctonus frontalis by use of a population aggregating pheremone.
Contrib. Boyce Thompson Insst 23:
Graham, K. 1968. Anerobic
induction of primary chemical attractancy for ambrosia beetles.
Can. J. Zool. 46: 905-8.
Happ, G. M., C. M. Happ and J. R. J. French 1976.
Ultrastructure of the mesonotal mycangium of an ambrosia beetle, Xyleborus
dispar (F) (Coleoptera: Scolytidae).
Int. J. Insect. Morpol. Embryol, 5(6):
Hopping, R. 1922. Coniferous
hosts of Ipidae of Pacific Coast and Rocky Mountain region. Can. Entomol.
Jack, I.D. 1964. Observations
on the biology of the shot hole borer and the ambrosia beetle in tree
fruit orchards in the Okanagan valley of British Columbia, 1963-4.
Unpublished report by the Ent. Branch of the British Columbia Dept.
of Ag., 30p.
Johnson, N.E. and P.G. Belluschi 1969.
Host-finding behavior of the Douglas-fir beetle.
J. of For. 67: 290-95.
Linsley, E. G., and G. F. MacLeod 1942.
Ambrosia beetles attacking deciduous fruit trees in California.
J. of Econ. Ent. 35(4): 601.
Maramorosch, K., L. F. Martorell, J. Bird and P. L. Melendez
1972. Platypus rugulosus (Platypodidae) and Xyleborus ferrugineus (Scolytidae) and certain diseases of coconut
palms in Puerto Rico. N.Y.
Ent. Soc. J. 80(4): 238-40.
Mathers, W. G. 1940. The
shot hole borer, Anisandrus pyri
(Peck), in British Columbia (Coleoptera, Scolytidae), Can. Ent. 72: 189-90.
McMullen, L.H. and M.D. Atkins, 1962.
On the flight and host selection of the Douglas-fir beetle, Dendroctonus
pseudotsugae Hopk. (Coleoptera: Scolytidae).
Can Ent. 94: 1309-25.
Miller, J.M. and F. P. Keen 1960. Biology and control of the Western Pine Beetle.
U.S.D.A. Misc. Publ. 800, 381p.
Moeck, H.A. 1970. Ethanol
as the primary attractant for the ambrosia beetle Trypodendron
lineatum (Coleoptera: Scolytidae). Can. Ent. 102: 985-95.
Muraleedharan, N. and C. Kandasamy 1981.
A new host record for the shot-hole borer Xyleborus
fornicatus of tea South India. Ass.
For Adv. Of Ent 6(2): 127.
Phillips, T.W., A. J. Wilkening, T.H. Atkinson, J.L. Nation,
R.C. Wilkinson and J.L. Foltz 1988. Synergism
of turpentine and ethanol as attractants for certain pine-infesting
beetles (Coleoptera). Ent.
Soc. Of Am. 17(3: 456-62).
Pittman, C.B., J.P. Vite, G. W. Kinzer and A. F. Pentiman,
Jr. 1969. Specificity of
population aggregating pheromones in Dendroctonus,
J. Insect Physiol. 15: 363-6.
Renwick, J.A. and J.P. Vite 1970. Systems of chemical communication in Dendroctonus. Contrib.
Boyce Thompson Inst. 2-(13): 283-92.
Roeper, R.A. and J.J.R. French 1981.
Growth of the ambrosia fungus Ambrosiella
hartigii on various nitrogen sources in association with the beetle Xyleborus
dispar. Micologia, Bronx, N.Y., New York Bot. Garden, Vol.
Ranasinghe. M.A.S.K. and R.L. Wickremesinghe 1988.
Use of acetates to induce host resistance to Xyleborus
fornicatus (Coleoptera: Scolytidae)
attacking tea. Proc. Br.
Conf. Pests Dis. London: British
Crop Protection Council v. 1 pp. 251-6.
Rudinsky, J.a. 1963. Response
of Dendroctonus pseudotsugae
Hopkins to volatile attractants. Contrib. Boyce Thompson Inst. 22: 22-38.
Rudinsky, J.a. 1966A. Scolytid
beetles associated with Douglas fir: Responses to terpenes. Science
Rudinsky, J.A. 1966B. Host
selection and invasion by the Douglas fir beetle, Dendroctonus
pseudotsugae Hopkins, in coastal Douglas fir forests.
Can. Eng. 98: 98-111.
Rudinski, J.A. 1970. Sequence
of Douglas fir beetle attraction and its ecological significance.
Contrib. Boyce Thompson Inst. 24:
Rudinski, J.A. and G. E. Daterman 1964.
Field studies on flight patterns and olfactory responses of
ambrosia beetles in Douglas-fir forests of western Oregon.
Can. Ent. 96: 1339-52.
Rudinski, J.A. and I. Schneider 1969.
Effects of light intensity upon the flight pattern of two Gnathotrichi
species. Can. Ent. 101: 1248-55.
Rudinski, J.A. and J.P. Vite 1956. Effects of temperature upon the activity and behavior of the
Douglas fir beetle. For. Sci.
Sjvapalan, P. and V. Shivanandarajah 1977.
Inhibitory effects of extracts from seeds and roots of tea, seeds, Sapindus
emarginatus, azasterols and
nonsteroidal amines on the development of Xyleborus fornicatus in
vitro. Ent. Exp. Appl. 22(3):
Sivapalan, P. 1969.
Control of the shot-hole borer of tea Xyleborus fornicatus (Eichh.):
final report on research conducted under grant authorized by U.S.
Public Law 400. Tea Research
Institute of Sri Lanka, 64.
Souto, D.J. 1974.
Studies on the initial host selection behavior of Scolytids
associated with a second growth Douglas fir forest.
Unpublished Masters thesis, Colege of Forest Resources, University
of Washington, 82.
St. George, R.A. 1929.
Weather, a factor in outbreaks of the Hickory Bark Beetle.
J. of Econ. Ent. 22: 573-80.
Swaine, J.M. 1918.
Canadian bark beetles. Dom.
Can. Dep. Agric., Ent. Brch. Tech. Bull. 14(2).
Vite, J.P. and D.L. Wood 1961.
A study on the applicability of the measurement of oleoresin
exudation pressure in determining susceptibility of second growth
ponderosa pine to bark beetle infestation.
Contrib. Boyce Thompson Inst. 21:
Vite, J.P. and G. B. Pitman 1968.
Bark beetles aggregation: Effects
of feeding on the release of pheromones in Dendroctonus and Ips.
Nature (London) 218: 169-70.
57. Wickremasinghe, R.L. and K.
Thirugnanasuntheram 1980. Biochemical
approach to the control of Xyleborus fornicatus (Coleoptera:
Scolytidae), Plant Soil. The
Hague 55(1): 9-15.
J.O. 1988. Occurrence of Xyleborus
ferrugineus (Fabr.) (Coleoptera:
Scolytidae) on yam tubers in Nigeria.
Insect Sci. Apl. 9(1): 41-2.
[i] Not to be confused with the
bark beetle, Scolytus rugulosus (Muller) (Coleoptera:
Scolytidae) of the same common name.
Scolytus is in a separate tribe of the same subfamily.
The important difference between bark beetles and ambrosia
beetles is food source and the area of utilization within a host.
Copyright 2009 Chestnut Growers of America, Inc.