Firewood Insects Usually Not at Home Indoors
Hundreds of insect species can inhabit the wood of our native and ornamental trees. However, the great majority of cases involve a few basic groups: roundheaded and flatheaded wood borers; bark beetles; carpenter ants; and powderpost beetles.
With few exceptions, insects found within California firewood will not survive indoors and are only capable of infesting well-dried logs with intact bark. The primary problems with firewood insects involve a few species of bark beetles that can develop in firewood and later infest healthy trees.
By far the most important of these insects is the mountain pin beetle, which kills large numbers of trees (primarily Ponderosa pine) in natural forest areas. Elm bark beetles and, rarely, ips beetles also may threaten healthy trees after emerging from firewood. Simple precautions can prevent injury by these firewood insects.
Here are some common firewood and house-log insects:
Wood borers are the most frequently observed insects infesting firewood and house logs. Most common are roundhead borers, also known as long-horned borers or sawyers. Adult stage is a medium to large beetle (1/4 to 2 inches), often with long antennae that can exceed the body length. Common roundheaded borers are gray-brown or with black speckling or deep blue-black.
Because of their long life cycle, borers can be present in wood for a year or longer. They do not emerge and attack healthy trees.
Western species normally do not recycle in the same wood that produced them. Furniture, wall framing or other seasoned woods are not suitable for wood borer attack. Despite producing what may seem like great quantities of dust, borers rarely tunnel extensively enough to cause structural failure. Adult borers found inside the home may look ominous and pinch the skin if handled but are not dangerous.
Bark beetles commonly infest dead or dying trees and then appear in firewood produced from such trees. Several well-known tree killers and disease vectors are the mountain pine beetle, European elm bark beetle and ips beetles.
Most bark beetles have a one-year life cycle, but a few can complete generations in two-month intervals. Bark beetles cannot reproduce in household wood products.
Powderpost beetle infestations of structural wood and furniture are uncommon but can be serious. Native species of these insects do occur naturally in dead tree limbs and dry seasoned wood.
Intact, sound logs are not used by carpenter ants. Rotting, water-damaged wood is used by these ants to nest within, and these logs rarely are utilized for firewood. Native populations of carpenter ants may develop within old, rotting wood that has been stored improperly for long periods.
Unfounded concern is wide-spread with moving termites in firewood or other wood products. Termites nest underground and under natural conditions rarely infest firewood and timber products. Occasional termites found within this wood do not contain reproductive stages of the termite. Furthermore, the low humidity in houses cause the “stragglers” in firewood to quickly dry out and die.
Firewood insects do not normally pose any hazards to humans, household furnishings, or plants. This is particularly true for the wood borers, the most conspicuous group of firewood insects. It is hard to witness the activity of borers without feeling a need to take action, but in reality borers speed up the drying process and promote better burning.
Firewood storage and collection
Problems with firewood insects emerging in the home are best handled by storing firewood outdoors until needed. Outdoor storage will greatly slow insect development during the winter and limit the opportunity for insects to emerge inside a home. The occasional insects that do manage to emerge indoors can be controlled by vacuuming.
Storing wood in a manner that accelerates drying also is important in limiting firewood insect infestations. Stack wood so that air readily flows through the pile. Well-dried wood will not invite bark beetle attack, and the drying process can kill many developing bark beetle larvae if already present in the wood. When collected firewood is known to harbor mountain pine beetle or other undesirable species, the best option is to burn the wood before adult beetles begin to emerge in mid-July; elm bark beetles emerge from elm logs in mid-May.
To avoid wood infested by these insects, choose trees for cutting that have been dried for at least one year or that have noticeably loose bark. If log piles are small and located in a sunny area, firewood insects can be killed by covering the pile with a clear plastic tarp. The high temperatures produced will kill many insects inside the wood. Control of insects in logs at the pile’s top may exceed 50 percent, but insects in lower logs generally are not affected.
A more difficult but highly effective means of killing most firewood insects is to remove the bark. Debarking also will prevent re-infestation and speeds drying.
The Yosemite Gold Team
CA Broker DRE license #00975527