Week 4 - Day 20 - Timber Borers
ESSENTIAL READING BEFORE COMMENCEMENT OF COURSE:
Urban
Pest Management in Australia: 2004
Edition, UNSW Press, Sydney
by
J Gerozisis and P Hadlington
- Chapter 18 - Pages 205 to 220.
Chapter 18 – Borers - pests of living trees and fresh logs - wood moths - economic significance - biology and species - treatment - wood wasps - economic significance - biology and species - treatment - greenwood longicorns - economic significance - biology and species - treatment - jewel beetles - economic significance - biology and species - treatment - weevils - economic significance - biology and species - treatment - ambrosia beetles - economic significance - biology and species - treatment - bark beetles - economic significance - biology and species - treatment - pests of moist and partly dry wood - augur beetles - economic significance - biology and species - treatment - pests of dry seasoned wood - powderpost beetles - economic significance - biology and species - treatment - furniture beetle - economic significance - biology and species - treatments - queensland pine beetle - economic significance - biology and species - treatment - European house borer - economic significance - biology and species - treatment - two-tooth longicorn - economic significance - biology and species - treatment - control of bark and wood insect pests - yellowhorned clerid - whitebanded clerid - parasitic wasps - straw itch mite - sapstain - black cockatoos - non-chemical methods of control - heat - freezing - submergence in water - radiation
Timber Borers can be conveniently divided into three major
categories: Bark & Wood Damaging Insects; Insect Pests
of Moist Wood and Insect Pests of Dry Wood.
Bark & Wood Damaging Insects
Insects, which damage the conductive tissue of the tree,
namely the phloem-cambium region, generally fall into the
Orders Coleoptera and Lepidoptera. The larval stages
of insects belonging to these orders are the destructive
stages, having mandibulate mouthparts and spending part,
if not the entire life cycle, in the conductive tissue. When
present in large numbers these insects may completely destroy
the phloem-cambium region, killing the tree by virtually
ringbarking it. Usually other insects must debilitate
a tree before these pests of the conductive tissue can
gain entry. Injury by fire, cultivating instruments,
or in fact any mechanical means, makes a tree susceptible
to attack by these pests.
COLEOPTEROUS INSECTS
Longicorns
Longicorn beetles are characterised by their long flowing
antennae, elongated body and eyes which are kidney-shaped
and partly surround the bases of the antennae. They
lay their eggs in the injured sections of the tree and the
young larvae, which hatch feed in the conductive tissue. This
contains carbohydrate material. When fully fed, the
larvae penetrate the sapwood to pupate. While in the
sapwood they are protected from birds and most predatory
and parasitic insects. When they have changed to the
adult stage they core their way out through the bark leaving
an oval hole, and commence the life cycle again. There are
a number of species of longicorns, some of them showing host
specificity. The yellow longicorn, (Phoracantha
recurve) which attacks a variety of Eucalyptus spp.,
is perhaps the most abundant species along the coast of N.S.W.
Although differences exist in the habits of the various species,
they are all essentially phloem-cambium feeders. Some
of them spend very little time in the phloem- cambium area,
moving to the centre part of branches and main stems early
in their larval life. The damage by longicorns is often noticed
in structural timbers, particularly when used for studs. The
insects which were originally present in the timber in the
pupal or late larval stage, emerge through plaster walls,
making oval holes about 6 mm across the long axis. Such
damage usually occurs within 1-6 months of the erection of
the house and involves no structural weakness to the timbers
beneath the plaster. It is usually only necessary to
repair the holes after emergence of all the beetles has taken
place.
Jewel beetles
Several jewel beetles attack trees, which have been damaged
by fire or other mechanical means. The larvae are
active in the phloem-cambium region until they are finished
feeding and then move into the sapwood to pupate. The
channels are similar to those of longicorns except the
frass is more tightly packed and the channels are narrower
than those of longicorns. They emerge through oval
holes in a similar way to longicorns. The species most
commonly encountered by the pest control operator is the
cypress pine jewel beetle. There are two species,
the small cypress pine jewel beetle, (Diadoxus erythrurus) measuring
about 12-18 mm in length, and the cypress pine jewel beetle, (Diadoxus scalaris) which
is about 18-25 mm in length. Evidence of attack
usually follows large fires in cypress pine areas when
the damaged timber is sawn and marketed. When attack
by cypress pine jewel beetles is noticed in weatherboards
or flooring no treatment is required. Usually jewel
beetles emerge from the timber 1-6 months after being placed
in service.
Bark beetles
Bark beetles are small insects measuring 3-6 mm in length,
feeding in the phloem-cambium region. They etch the
sapwood, in some cases quite deeply but fortunately very
few of them attack ornamental trees. The cypress
bark beetle, (Phloeosinus cupressi) and the black
pine bark beetle (Hylastes ater) are the most common
species in Australia. They attack ornamental cypresses
and pencil pines, causing their death unless controlled
early in their development life.
Weevils
Some weevils, which attack wood in the forest, work initially
in the phloem-cambium and then complete their larval development
in the wood such damage is usually characterised by the
tightly packed frass, which breaks off in pieces. Weevil
workings are always round and invariably occur in moist
wood.
The express bark weevil Aesiotes leucurus that measures
12-18 mm in length, is a pest of the phloem-cambium region
of ornamental cypresses and pencil pines. It attacks
trees, which have been injured or debilitated through growing
close to other trees of the same species and competing for
soil. Nutrients in the same area. The eggs are laid
in the bark and the young larvae feed in the phloem-cambium
region until they are fully fed, when they construct a small
chamber immediately beneath the bark. This chamber
is lined with strips of wood and when pupation is complete
the weevil emerges by cutting a round hole about 6 mm in
diameter.
Anobiid bark beetles
The pine bark anobiid (Ernobius mollis) is the most
commonly occurring anobiid bark beetle present in Australia. It
attacks trees, which are dying, or those, which have been
ringbarked. The beetles work in the phloem-cambium
region while the bark is intact. As attack progresses
they will excavate the sapwood to a depth of up to 6mm. When
flooring is placed in service, round emergence holes caused
by anobiid beetles may appear in linoleum or other covers. When
infested Pinus radiata (Monterey pine) is made
into door or other joinery timbers and bark is left on the
internal core, these beetles will emerge through a polished
veneer surface.
Bostrychids
Bostrychids attack moist sapwood containing starch but it
is not uncommon to find dying branches of eucalypts and
other trees containing starch in the sapwood attacked by
the bostrychids. They bore round holes through the
bark into the sapwood. The eggs are laid in the woody
tissue and the larvae develop in the moist wood.
LEPIDOPTEROUS INSECTS
This Order contains the wood moths, the larvae of which
feed in the phloem-cambium during the early part of their
life, entering the sapwood and sometimes the heartwood for
pupation. The wood moths fall naturally into two groups.
the cossid type and the xyloryctid type. These represent
insects belonging to the families Cossidae and Xyloryctidae,
differing both in habits and structure of the larvae and
adults.
Cossid type
These are characterised by large excavations of the phloem-cambium
leading to a hole, which penetrates the sapwood or heartwood
in either an upward or downward direction. Xyleutes encalypti, the
wattle goat moth, attacks Acacia spp. and constructs
its pupation channel in an upward direction to prevent water
entering and drowning it while in the pupal stage. Xyleutes
macleayi, another large species of wood moth, attacks Eucalyptus spp.,
in a similar way to Xyleutes encalypti in wattles. The
Australian goat moth, a smaller species, attacks ornamental
trees such as sugar gums and angophoras, completely excavating
the phloem-cambium region of a tree. They enter the
sapwood to pupate and emerge later as mottled-grey moths.
Xyloryctid type
These are characterised by constructing over their workings
in the phloem-cambium region a mat of chewed-up wood and
web material. This prevents the access of water to
a channel they construct in the woody tissue of the tree. Species
of this group commonly attack fruit trees and gum trees.
Wood wasp Sirex noctilio
Since 1952 it has been established that Sirex is present
in Victoria, particularly around Port Phillip Bay area. It
has now spread to southern N.S.W. Sirex attacks
trees by inserting its ovipositor to some depth in the wood
and depositing one or perhaps two eggs at each oviposition
puncture. A fungus is inoculated into the wood with
the eggs and the mycelial growths from this fungus spread
through the wood and block up the conductive tissue or xylem
vessels. The tree does not die from a mechanical injury
caused by the insect larvae, but from the mass of mycelial
growth, which prevents the translocation of water and mineral
salts up the tree. Sirex larvae feed on the fungus-attacked
wood and when finished feeding they pupate and emerge as
wasps.
INSECT PESTS OF MOIST WOOD
Insects, which attack moist wood, are not always serious
pests although some of them will continue their activity
after the timber has dried. It is important that the
various groups of insects, which attack moist wood, be recognised
by their damage, immature and mature forms. Insect
pests of moist wood are conveniently divided into five main
groups:-
- Ambrosia beetles.
- Bostrychid wood borers.
- Jewel beetles.
- Longicorns.
- Weevils.
Ambrosia beetles or pinhole borers
Insects belonging to the family Platypodidae are characterised
by having a well-marked head, thorax and abdomen region
when viewed from above, an elongate body and the tarsi
of the legs are quite long, usually longer than the tibial
segment. The family Scolytidae contains shorter beetles,
having their head concealed beneath the prothorax and the
tarsi are smaller than the tibial segments. The Platypodidae
invariably stain the timber while many species of the Scolytidae
do not leave stains. However, the habits are similar
and they can be considered together. There are two main
groups of Ambrosia beetles belonging to two different families.
Economic importance
Pin hole borer attack in furniture timbers, while not adversely
affecting the strength or service life of the article, does
affect its appearance and it is conceivable that sales suffer
from the mere presence of borer holes even when these are
located on the interior part of the manufactured article.
Foreign timbers, particularly those from the Pacific Islands,
show attack by ambrosia beetles. Pacific Maple used
for various joinery purposes such as architraves, doors,
sills, etc., frequently shows attack by a pinhole borer which
does not stain the wood. This damage may be confused
with that of Lyctus (powder post beetles) and has
frequently affected subsequent sales of this timber. Other
timbers from Malaya, New Guinea, etc., show attack by pinholes
borers of the Platypodidae type in which case staining is
prevalent. Since this insect is dependent on moisture in
the wood, dry wood is not attacked nor is attack sustained
during its service life. There are rare instances,
such as timber used for wine casks or water tanks, where
pin hole borer attack may continue, particularly when the
timber is constantly wet. The holes persist in dry
timber but this should be no deterrent to its various useful
purposes.
Appearance
The Platypodids and Scolytids are small insects, measuring
from 1.5 mm to about 6 mm in length. The beetles may
be elongate or cylindrical, depending on the family to which
they belong. Platypodids are elongate and Scolytids
shorter and cylindrical. The larvae are legless grubs,
having a scroll on the dorsal surface of the first thoracic
segment. The pupae are typical beetle pupae and located
deep in the timber, usually in specially excavated chambers.
Habits and life cycle
The female beetle bores into the timber to some depth, carrying
with it spores of a fungus which are left on the inside surfaces
of the tunnellings. In the presence of moisture the
fungal spores develop and fill the passageway made by the
female with mycelial growth (like cotton wool). The
male is usually located in the same tunnel as the female,
mating occurring outside the tunnel. Frequently both
male and female die in the tunnel, blocking it against entry
by predatory and parasitic insects.
The eggs are deposited near the end of the tunnel and the
young larvae which hatch feed on the fungus growing on the
internal walls. The larval stage usually lasts from
one to four months, depending on the species and when fully
fed the larvae pupate at the end of the parent gallery. They
emerge from the original hole and commence the life cycle
again. As the wood dries the fungus can no longer grow
and the insects die or leave the tunnel.
Bostrychid wood- borers
These insects attack timber whose moisture content is high,
usually between that required for pin hole borer and powder
post beetle infestation. They attack only the sapwood
and although infestation may have occurred in moist timber
they are able to continue their activity in timber which
has dried. However, they are not able to reinfest dry
seasoned timber. Therefore one generation only is possible,
as drying out takes from six weeks to six months after felling
and the life cycle from egg to adult usually takes 6-9 months.
Economic importance
Bostrychids attack only the sapwood containing starch and
will reduce this to dust provided the infestation is heavy
enough. Attack is common in case timber, logs or poles,
mine timbers (pit props), etc. In some cases where
the moisture content is high, such as in mines, bostrychids
will attack until the timber is destroyed; This may involve
several generations of insects. When bostrychids emerge
from hardwood bearers in newly erected houses or new additions
to homes they may cut out through flooring so that it appears
as if the flooring is being attacked. This often happens
in the case of cypress pine flooring over susceptible hardwood
bearers and joists. When emerging into a room they
may bore into soft pine fittings, furniture, sills, etc.,
but are not able to initiate further attack.
Appearance and habits
Bostrychid beetles, when viewed from above, appear to have
only two segments to the body as the head is concealed beneath
the prothorax. The antennae have a three segmented
club and are generally folded underneath the prothorax alongside
the head. The prothorax has backwardly projecting spines
on the front or anterior section. The elytra or wing
covers are frequently sharply cut away at the end and may
bear ornamentations. The larvae are similar to powder
post beetle larvae, being cured and having three pairs of
thoracic legs. There is no large spiracle on the second
last abdominal segment. The beetle lays its eggs in cracks
and crevices in the wood and also in the holes it drills. On
hatching, the larvae feed on the starchy sapwood and excavate
it until it is completely destroyed. They pupate fairly
close to the surface and emerge through round holes. The
beetles are not able to reinfest dry seasoned wood as the
larvae require high moisture content during their early developmental
stages. This is not critical later in their larval
life as attack is sustained in dry timber for the first generation.
Hosts
Bostrychids attack the sapwood of most hardwoods and brushwood’s
which contain starch. Such timbers as spotted gum,
blue gum, yellow carabeen, white birch, and many others are
attacked by bostrychids. Attack may take place either
in the mill yard, or if the timber is used unseasoned, while
it is in service in buildings.
Jewel beetles
Jewel beetles attack green trees or freshly felled logs,
the larvae working in the phloem-cambium region and
moving into the sapwood to pupate. Superficially
the damage resembles longicorns, the emergence holes being
distinctly oval. When the damage is seen in wood,
jewel beetles make characteristic crescent-shaped etchings
or markings on the surface of the tunnel. Longicorn
markings, made by their jaws, are straighter and do not
have the crescent-shaped appearance.
Jewel beetle larvae work in the phloem-cambium, feeding on
the nutritive materials, but some species such as the hoop
pine jewel beetle enter the sapwood early in their larval
life. Three main types of jewel beetles occur in houses
after erection –
Cypress pine jewel beetles
- Two species are involved in this group - the cypress
pine jewel beetle (Diadoxus scalaris) and
the small cypress pine jewel beetle (Diadoxus erythrurus). When
a house is erected these insects may emerge up to six
months after the timber has been utilised for flooring
or weatherboards. Sometimes linoleum and other
covers are damaged by the emergence of these insects.
The beetles of this species are yellow, green and black;
dorso-ventrally flattened and have short serrated antennae. The
larvae are characteristically flat-headed, the head resembling
that of a cobra snake. Once emergence has taken place,
no further trouble occurs, as this insect requires the
phloem-cambium region for the initiation of attack and
the nutrition of their larvae.
- The hoop-pine jewel beetle (Prospheres aurantiopictus). The
hoop pine jewel beetle attacks hoop pine when it is standing
in the forest and the beetles may emerge from timber in
service up to 20 years after the timber has been utilised. Hoop
pine is frequently used for framing in furniture and doors
and infested timber sometimes escapes notice at the mill. Such
timber sustains the larvae of the hoop pine beetle until
it is ready to emerge and frequently this occurs through
polished surfaces. Considerable destruction of the
timber may occur and furniture is seriously defaced. Hoop
pine may also be used as flooring and in such cases extensive
channelling may occur but seldom does collapse result.
The beetles are variable in colour. Some are entirely
black while others have orange markings on the elytra or
wing covers. There is no correlation between sex
and the variation in coloration. The beetles measure
about 12-18 mm in length and have the characteristic dorso-ventrally
flattened body and serrated antennae. The larvae
are characteristic hammer-headed buprestid larvae.
- Oregon jewel beetle (Buprestis aurulenta). Oregon
is sometimes damaged by a jewel beetle. It is not
uncommon for these insects to emerge from timber after
some 30-40 years of service. Considerable damage
may occur and the appearance of the large oval holes about
6mm across the long axis is somewhat alarming. Buprestis
aurulenta is a bright green colour with a small patch
of orange on the anterior edge of the thorax. It
usually emerges from timber of some age and control measures
are seldom required. The early stages of attack are
seldom detected because its incidence in houses is negligible.
Longicorns (Family-Cerambycidae)
Various longicorn damage has already been discussed. The
larvae of these are pests of the phloem-cambium region but
the sapwood may be seriously degraded by the larvae penetrating
it to pupate. When this timber is used in houses the
insect may emerge through plaster and other interior wall
covers. The adult is typical of the group, having long
flowing antennae, eyes which partly surround the bases of
the antennae and a rather elongated body. They attack
a variety of tree species, eucalypts, pines and brush woods.
Weevils (Family - Curculionidae)
Some weevils attack debilitated trees and dead trees. Aesiotes
leucurus, the cypress bark weevil, which attacks Cupressus species
and various Pinus species, including Pinus radiata works
in the phloem-cambium region and excavates the sapwood to
a depth of about 6mm when constructing its pupal chamber. Its
damage cannot be confused with that of weevils such as Euthorhynus
meditabundus. This insect works in the sapwood
and heartwood of debilitated trees. The holes are perfectly
round and packed with mud-like excrete. The weevil has a
long proboscis characteristic of most weevils and attacks
hoop pine and the various Cupressus species.
Control is seldom required, as the timber is usually not
seriously affected.
INSECT PESTS OF DRY WOOD
Insect pests of dry wood are important pests of buildings
and houses. Mainly they are pests of the sapwood but
insects such as the European house borer, the two-toothed
longicorn, and the various species of Anobiids can also penetrate
the heartwood.
Longicorns (Family-Cerambycidae)
The species of longicorns dealt with here should not be confused
with those which attack the green tree and require the
phloem-cambium region for larval development. In
the absence of these tissues the longicorns are unable
to complete their development and seldom do the female
beetles oviposit in wood not containing bark. The
two dry wood longicorns in Australia are introduced species.
The Two-toothed Longicorn Ambeodontus tristis
This insect has been introduced from New Zealand where it
is a pest of flooring and structural timbers. Control
measures are frequently carried out against the two-toothed
longicorn in New Zealand. In N.S.W. the two-toothed longicorn
is mostly found in the coastal suburbs of Sydney, although
instances of attack occur in areas from the sea. It
attacks N.Z. rimu flooring and does not appear to have
been found in structural timbers, mainly because N.Z. rimu
has not been used extensively for such purposes. With
the greater utilization of pine timbers it is possible
that the two-toothed longicorn beetle will increase. Flooring
is often heavily attacked and there appears to be a correlation
between the high humidity in this region and the incidence
of infestation.
Appearance and life cycle
Ambeodontus tristis beetles vary in size from about 12 to 30
mm. The size difference appears to be related to the competition within
the timber i.e. timber containing few insects yields larger beetles than when
the population is high. The beetle is uniformly red-brown in colour,
and typical of most longicorns it has long flowing antennae, elongated body,
eyes which are kidney-shaped and partly surround the bases of the antennae
and lateral and dorsal spines on the thorax. The larva is characteristic
of all longicorn larvae, having a broad thoracic region tapering to the terminal
section. The head capsule is small and distinct and the larva is legless.
The female beetle lays her eggs in cracks and crevices in the wood and the
young larvae on hatching develop mainly in the sapwood. Later in life
the larvae are able to penetrate the heartwood and it is not uncommon to see
this area also completely destroyed. They pupate close to the surface
and emerge through oval holes about 6 to 7.5 mm across the long axis. The
life cycle involving the egg, larva, pupa and adult, is completed in two to
four years, although under favourable conditions it is possible that a one-year
life cycle will occur. The two-toothed longicorn attacks mainly New Zealand
rimu in Australia, but attack may also occur in various pine timbers such as Pinus radiata.
The European House Borer Hylotrupes
bajulus
Although this insect has occurred in Melbourne, Cooma, and
Sydney it only appears to be firmly established in some parts
of Queensland. This is partly due to the fact that,
in every instance, fumigation of the entire structure or
dwelling has been carried out. It is a pest of structural
pine timbers in Europe, Great Britain and Scandinavian countries,
where it attacks until the timber is reduced to powder. In
South Africa, where the insect was introduced around 1930,
it has spread over many coastal areas. It does not
appear to do well or be able to establish itself in the more
inland regions of South Africa. In such areas as Port
Elizabeth, the insect is able to complete its life cycle
in a shorter time than in Europe and, as a result, structures
have collapsed, necessitating legislation, which requires
pine timbers to be treated before being used for buildings.
Appearance and life cycle
The beetle is dark brown, having four small white patches
on the elytra or wing covers. The eyes partly surround
the bases of the antennae but while the antennae are typical
of most longicorns they are not long and flowing as in Ambeodontus. The
beetle measures from 12 to 25mm in length, depending on its
food during the larval stage. The larva is a typical
longicorn, measuring up to 30 mm in length. The female lays
her eggs in cracks and crevices in the timber and the larvae
on hatching eat into and destroy the sapwood. Usually
attack is restricted to the sapwood but the heartwood may
be destroyed when the numbers of larvae are large. They
pupate close to the surface and the beetles emerge through
oval holes about 6 to 7.5 mm across the long axis. The
life cycle usually takes from 2 - 11 years, depending on
the region of occurrence. For instance, in Northern
Europe the life cycle is generally completed in 5-11 years,
but in South Africa the period is only 1 - 3 years. This
shorter life cycle is attributed to warmer temperatures and
higher humidity’s. Hylotrupes bajulus attacks Pinus spp.
e.g. Monterey pine, Ables spp. and Pseudotsuga spp.
e.g. Oregon, but it has not been recorded attacking Araucaria spp.
or Podocarpus spp. e.g. N.Z. white pine. The
European house borer does not affect Eucalypts and most pored
timbers.
Control
Since the European house borer is apparently not established
in most parts of Australia, reports of infestation should
be passed on to the relevant State Government authority or
to AQIS (Australian Quarantine and Inspection Service) In
this way an accurate identification of the insect causal
agent can be made and the appropriate control measures taken
in accordance with government requirements.
Lyctidae
Beetles belonging to the family Lyctidae are commonly known
as powder post beetles. There are several species,
all having similar habits and attacking the same types of
timber. The most common species in Australia is Lyctus brunneus but Lyctus
discedens also occurs to some extent. The separation
of these two species requires the assistance of a specialist
entomologist.
Economic importance
Lyctids attack the seasoned sapwood of certain susceptible
timbers. This sapwood must contain. Starch in sufficient
amounts to permit the young larvae to feed and complete their
development. Certain timbers such as Blackbutt do not
have sufficient starch to allow infestation and are therefore
resistant to the powder post beetles. The heartwood
is devoid of starch, being composed of dead cells, and is
therefore not attacked under any circumstance by powder post
beetles. The beetles may emerge through the heartwood
but it is not destroyed by their activity. Pine timbers i.e.
non-pored woods, are not attacked by the powder post beetles
and are considered to be immune. Hardwoods (eucalypts,
brushwood’s and other pored woods) when they contain
starch in the sapwood may be attacked by the powder post
beetles. The starch content is an extremely variable
factor and some tree species which are considered highly
susceptible may at times contain very little or no starch
in the sapwood and remain un-attacked by powder post beetles
during their service life. Powder post beetle attack occurs
in wood, which has between approx. 8% and 25% moisture content. The
equilibrium moisture content of timber in service is somewhere
between 12% and 16% and varies within small limits with the
atmospheric moisture content. For instance, timber
in service in the western districts of N.S.W., Queensland
and Victoria, would have lower moisture content than the
same species on the coast. When attack occurs in small dimensional
pieces of timber such as those found in tiling battens, ceiling
battens, various pieces of furniture and joinery timbers,
the sapwood may be so extensive that almost complete destruction
occurs. In large dimensional pieces of timber such
as rafters and noggings and practically any structural timber,
the sapwood is usually only of small extent and its destruction
would not adversely affect the strength of that particular
member and subsequently the condition of the building. Various
acts of State Government eg. Timber Marketing Act (NSW)
and the Timber Users Protection Act (QLD) control the use
of Lyctus susceptible timber. These Acts
limit the-use of Lyctus susceptible sapwood
inasmuch as it constitutes a breach to use susceptible timber
for furniture, flooring and for other joinery purposes. They
allow 25% of the perimeter of certain structural timbers
to be composed of susceptible sapwood because it is realised
that, if 25% of the members was destroyed the strength would
not be adversely affected.
Appearance and life cycle
The beetle varies in size from 3 to 6mm in length, is somewhat
flattened and has its body divided into a distinct head,
thorax and abdomen. The beetles are a dark red-brown
colour and are characterised by having a twosegmented
antennal club. The antennae are short and often folded
beneath the head when the- beetle is disturbed or at rest. The
larvae when fully fed vary from 3 to 6 mm length and are
curved. During the first four to five days after hatching
they are not curved but later develop this characteristic. They
are cream or white in colour and are characterised by having
the spiracles on the second last segment of the abdomen enlarged. This
feature is used to separate them from the larvae of Anobium punctatum (furniture
beetle). The female beetle lays between 30 and 150 eggs,
these being deposited in the end pores only of susceptible
sapwood. The pores of the timber must be of sufficient
size to accommodate the ovipositor (egg laying apparatus)
of the female. There are timbers such as coachwood,
which are considered to be resistant because their pores
are too small to allow the entry of the ovipositor. Tracheids
in pines are too small to allow the entry of the ovipositor
and for this reason all pines are considered to be immune
to attack. The larvae on hatching bore parallel with
the timber, feeding only in the sapwood. Their main
food is starch, which occurs in granules in this outer area
of the wood. While their channels are mostly longitudinal
with the grain of the timber they sometimes move transversely. The
holes are packed with dust or frass, which is fine and flour-like
and can hardly be felt when rubbed between the fingers. When
fully fed the larvae come close to the surface of the wood
and pupate. In this way they have only a short distance
to emerge from the timber. They emerge through round
holes about 1.5 mm in diameter. The beetles mate outside
the timber and are active mainly at night, concealing themselves
beneath pieces of timber or in old flight holes during the
day. The life cycle occupies between 3 - 18 months, but mostly
it is completed within 6 - 12 months in the coastal areas
around Sydney, Brisbane and Melbourne.
The Furniture Beetle Anobium
punctatum
This species of beetle appears to have had its origin in
Europe but is now widely spread throughout the world. It
was probably introduced into Australia in antique furniture
or timber. It is prevalent along the eastern coast
of Australia but does not appear to occur inland. Its
distribution is affected by the relative humidity, which
determines the equilibrium moisture content of timber. West
of Lithgow in N.S.W. the incidence of furniture beetle infestation
is low. Most of the western districts of the eastern
States are completely free of furniture beetle infestations.
The furniture beetle prefers pine woods, mainly Pinus
radiata, Pinus elliottii, Araucaria cunninghamii and
various species of Podocarpus. Oregon
is attacked but it is seldom attacked to the extent that
its structure is completely destroyed as in the case of Pinus spp. The
resin bands in Oregon appear to deter the infestation, which
is confined to the softer regions. Pored timbers are
also attacked but less frequently than the pines. Spotted
gum, for instance, may be attacked but in such cases the
infestation is restricted entirely to the sapwood and confusion
with powder post beetle infestation should not occur, as
the frass or pellets are coarser in the case of Anobium.
While most pored timbers are resistant to attack, it must
be realised that Anobium, even though occurring rarely
in those timbers, must not be overlooked when identifying
the cause of an infestation. There is no authoritative
record of cypress pine being attacked by the furniture beetle.
While the furniture beetle prefers the sapwood, it will,
however, attack the heartwood but usually this only occurs
when the sapwood has been completely eaten away. Timber
cut from young trees appears to be more susceptible than
that from older trees. Most of the instances of collapse
of flooring and sagged ceilings have been due to infestations
of this insect. This beetle will work in timber until
it is completely destroyed. Sometimes parasites and
predators affect the progress of the infestation but usually
this occurs after considerable destruction has been done. It
has been noted that timbers of some age beyond, say, 15 years,
are mostly attacked and it is presumed that these woods were
more susceptible after they had "aged". Research
has indicated that fresh pine is as susceptible as old pine. The
reason why attack is not noticed appears to be due to the
longer life cycle of this insect and the avoidance of bringing
infested wood into new homes. After some years the
householder seems less reluctant to bring in the antique
than he did during the early life of the house. The
removal of resins and other materials in pinewoods does not
appear to influence its susceptibility.
Appearance and life cycle
The beetles lay their eggs in cracks and crevices of wood
surfaces and in the case of polished or painted timber they
lay in abraded surfaces. The larvae, which hatch work
longitudinally with and transversely to the grain of the
wood. When finished feeding the larvae come close to
the surface, construct small chambers and pupate. They
emerge through round holes about 1.5 mm in diameter. Usually
these holes appear more abundantly on the under surface of
floors and the inner surface of wooden panelling. The
appearance of a few holes on the upper surface of flooring
invariably indicates a greater number of flight holes on
the under surface. It is not possible to get a true
indication of the severity of attack by merely viewing the
upper surface of the flooring. The life cycle in Australia
is usually completed in 1 - 3 years, but in Europe and Great
Britain the period may be extended to 5 years. This
variability appears to be related to a combination of both
temperature and humidity.
Dampwood borer Hadrobregmus
australiensis
This borer attacks many species of timber, both hardwoods
and pines which have been previously deteriorated by fungi. Attack
is restricted to the sapwood unless the heartwood has also
been deteriorated by fungi. It is of negligible importance
in Australia, but instances of attack may be confused with
old bostrychid damage. Usually homes showing attack
by the this borer need, or have at one time needed, ventilation
to remedy conditions of high humidity conducive to wood decay. Its
distribution in N.S.W. appears to be restricted to the coastal
region, particularly in built-up areas around Sydney. No
record of attack has been reported from other States but
it is important to remember that very little work has been
done on this insect in Australia and its occurrence may be
anticipated anywhere decay has occurred.
Appearance and life cycle
The beetle is dark brown in colour with the head concealed
beneath the prothorax in a similar manner to that of the
furniture beetle. It measures about 6-9 mm in length,
and lays its eggs in cracks and crevices in the wood. The
larvae resemble those of bostrychids but do not have the
enlarged thoracic region. The life cycle appears to take
1 - 3 years, but at this stage very little work has been
done on the habits and life cycle of this insect. The
main characteristic of this insect which enables it to be
separated from the bostrychids is the darkened appearance
of the pupal chambers in the wood. After some time
the dark pupal chambers turn almost black.
The Queensland Pine Beetle Calymmaderis
incisus
The furniture beetle occurs around Sydney and along the North
Coast of N.S.W. and into Queensland. In Queensland,
however, it is of lesser importance because its place is
taken by the Queensland pine beetle. The incidence
of the Queensland pine beetle becomes greater as one proceeds
north from Kempsey. It is not known to occur in Sydney,
although it is possible that, even if it were present, the
damage may be attributed to that of the furniture beetle. The
dust and workings are similar and it attacks the same types
of timbers. Its attack is confined to the sapwood,
although some instances exist where the heartwood is affected.
Appearance and life cycle
The beetles are oval and shiny brown and the prothorax which
conceals the head is not so pointed as that of the furniture
beetle. The beetle measures about to 3 to 4.5 mm in
length. The beetles have a three-segmented antennal
club and the larvae closely resemble those of the furniture
beetle. The life cycle is approximately the same as that
of the furniture beetle, being 1 - 3 years, the shorter period
being the usual in Queensland. The separation of the
damage from that of the furniture beetle requires the assistance
of a specialist and should be referred to a State Government
entomologist if identification is required. While most instances
of furniture beetle attack are attributed to Anobium
punctatum, some instances are due to other species
such as Nicobium castaneum and other species
in this genus. Here again it is necessary to refer
the damage to an entomologist for confirmation of such suspected
occurrences. The habits and distribution of these insects
are similar to that of the furniture beetle but differ in
appearance of the damage.
Miscellaneous Wood Borers
Sometimes wood is damaged in situ by insects which normally
attack foodstuffs or decaying animal or vegetable matter. Usually
such instances of infestation are close to storage or handling
facilities for food products. Mostly the damage is
due to the larval stages seeking a place to pupate. The
skin and hide beetles (Dermestids) frequently
seek out soft Oregon or pine timbers in which to pupate. The
pupal period often lasts many months, and the active insects
may emerge some months after the larvae have entered. Another
pest with similar habits is the sawfly (order Hymenoptera),
the larvae of which may leave the host tree and bore into
timber of nearby buildings. Other insects, which affect
timber, are the grain weevils, the cadelle (a grain
pest), the yellow mealworm and the flour beetles. These
may attack timbers of the structure in which the grain
is stored, or pupate in the timber, which frequently composes
the containers. These insects are considered secondary
pests but their damage must not be confused with that of
the primary wood borers whose larvae are capable of destroying
completely the structure of wood. However, it must
not be overlooked that these insects, when present in large
numbers, can seriously degrade wood and in some cases affect
its service life in structures.
MARINE BORERS
The best-known group of marine borers is that which includes
those molluscan borers known as "shipworms," or Teredo. This
is a bivalve mollusc of worm-like appearance, which is
of considerable importance in many seaports as a destroyer
of wooden-hulled ships and wooden harbour installations.
The female Teredo produces large numbers of free-swimming
larvae, which actively swim about in search of wood. As
burrowing proceeds, the gallery is lined with a calcareous
material. The "shipworm" can attain a length
of 45 cms or so and its burrow can be up to 25 mm in diameter. The
only external signs of damage are small openings made by
the larvae as they burrowed in. Two siphons emerge
from these holes allowing for the passage of sea water. At
the other end of the burrow, two small shells rasp away
the wood. Teredo feed on a combination of
cellulose and planktonic organisms. Another important group
of marine borers belongs to the Crustacean order Isopods. This
is a large group comprising approximately 4,000 species
most of which are marine. The marine borers, which
attack docks and pilings, are very similar in appearance
to their terrestrial relatives the slaters and measure
approximately 3 mm in length. The Isopod borers can be
found in large numbers boring into the timber surface,
the gallery first running obliquely and then parallel to
the timber surface. As they burrow they periodically
construct "manholes" giving access to fresh
seawater. When the outer 10 mm or so of timber has
been completely honeycombed, it is broken away by wave
action and subsequent tunnelling commences in the next
10 mm layer. A male and female can be found in each
gallery but only the female does the burrowing. Another
crustacean borer belonging to the group Amphipoda inhabits
these burrows, both species living together in an association
of mutual benefit. Attack by these crustaceans can
seriously affect pilings often causing them to develop
the characteristic "hour glass" appearance.
Useful website links:
http://www.ipminstitute.org/school_biblio_buildings.htm#Wood |
