Quick Facts...
- Wood borers are instrumental in beginning the breakdown processes
that prepare nutrients for reuse by subsequent plants.
- The presence of bark beetles, including Ips, is indicated by a brown
boring dust located at the base of the tree or masses of resin (pitch
tubes) on the trunk.
- Bark beetle activity in burn areas should be monitored and managed
to keep losses within acceptable limits.
- Wood borers only attack highly-stressed trees or wood pieces with
the bark still attached. The presence of wood borers is not a major
concern to healthy trees or other wood (such as furniture).
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| Adult longhorned beetle. |
This fact sheet discusses: organisms and damage commonly seen during
or immediately after a fire; and organisms and damage associated with
fire-affected trees (including salvaged logs and firewood) within the
first few years after a fire event.
During the fire and “mop-up” operations, many firefighters
report swarming insects. Collectively termed “fire bugs,” these
insects are harmless to people and are most often some type of wood borer.
The most common wood borers are longhorned beetles (Family Cerambycidae),
metallic wood boring beetles (Family Buprestidae, with members of the
genus Melanophila being the “fire bug”), and wood wasps (also
called horntails, Family Siricidae). Many wood borers use smoke as a pathway
to the recently-damaged or killed trees which they favor. This is their
ecological role and they are instrumental in beginning the breakdown processes
that prepare nutrients for reuse by subsequent plants.
Bark Beetles
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| Adult metallic wood borer. |
Within a year or two following the fire, many other organisms respond
to the fire-induced changes. Insects such as bark beetles colonize burned
trees that still have a viable inner bark. These beetles, including those
in the genera Ips (“engraver beetles”) and Dendroctonus (including
Douglas-fir beetle, red turpentine beetle, and mountain pine beetle),
can kill trees that otherwise would not have died from the fire affects
alone. A brown boring dust located at the base of the tree or masses of
resin (pitch tubes) on the trunk indicates the presence of these insects.
Homeowners may want to preventively spray high-value conifers damaged
– but not killed – by fire to prevent bark beetle attack. Also,
bark beetles can accumulate in burned trees and then spread to nearby
healthy trees causing even more damage. Therefore, bark beetle activity
in burns should be monitored and managed to keep losses within acceptable
limits.
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| Adult wood wasp (or horntail). |
Wood Borers
Wood borers develop inside damaged trees and emerge one to several years
after the initial egg-laying. The large, white, segmented wood borer larvae
are responsible for the munching sounds often reported by visitors to
burned areas or by owners of salvaged logs and firewood. Sometimes the
noise caused by their jaws scraping on wood under the bark can be heard
up to several yards away! In addition to these tell-tale sounds, wood
borer activity within snags or cut wood may be indicated by whitish, powdered
or granular, boring dust accumulating in bark crevices and at the tree
base. Wood borers only attack highly-stressed trees or wood pieces with
the bark still attached, so the presence and emergence of wood borers
is not a major concern to healthy trees or other wood (such as furniture).
Their only negative impacts are lumber degrade in special situations and
misunderstandings about their somewhat ominous appearance.
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| Ips boring dust. |
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| Dendroctonus pitch tubes. |
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| Larval cerambycids. |
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| Adult wood borer (Monochamus scutellatus). |
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| Cerambycid boring dust. |
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| Decay fungus conks. |
Other Insects and Fungi
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| Mushrooms found in openings. |
Insects to expect in fire-killed trees following bark beetles and borers
are carpenter ants. Unlike termites, they do not eat the wood but use
semi-rotten areas for colony nests.
Many fungi also respond after wildfires. Taking up residence in wounds
directly induced by the fire or created by wood borers, decay fungi quickly
colonize fire trees. The spore-producing bodies of these fungi (conks)
appear as woody projections or “shelves.” Mushrooms or conks
on the bark of a standing snag or downed log indicates rotten wood for
one to several feet above and below it.
Many conifer forest burns experience the widespread appearance of pine
fire fungus (Rhizina undulata). This fungus forms irregular, oval, brown
fruiting bodies on the charred soil. It may be abundant but not very easy
to see. Its purpose is to help process the duff and upper soil layers,
but it also can cause a root disease of conifer seedlings trying to form
the next forest.
Also, other fungi and mushrooms typical of so-called disturbed or “early
succession” sites may appear. Collectors of edible fungi should practice
caution and normal identification standards before eating anything found
at fire sites.
Of course, many other organisms can be associated with fire – this
publication gives just the highlights. Please direct further questions
to your local Colorado State Forest Service office.
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| Internal decay. |
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| Pine fire fungus on forest floor. |
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