HOUSEHOLD AND STRUCTURAL

 

Insects in Firewood

Timothy J. Gibb, Extension Entomologist

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Firewood is a popular source of fuel in many homes today. Often firewood is cut from dying or storm-damaged trees that are very attractive to many insects, especially wood borers. After wood is cut and stacked, it also can serve as a hiding place or overwintering area for a variety of other arthropod pests. Although most firewood pests pose no direct threat to the home, its contents, or its occupants, they can become annoying when they emerge inside the home. The following insects found inside the home may have originated with firewood.

WOOD-BORING BEETLES

Long-horned beetles (also called roundheaded borers) are the most common of the wood borers that infest firewood. They lay eggs in wood while it is still green and thus are usually already in the wood when it is cut for firewood. Larvae are whitish, legless grubs that have bodies that taper from the head to the tail. They may tunnel and feed for a year or longer depending on the moisture content of the wood, and the temperature of its surroundings. After the larvae have pupated (resting stage), the adults may emerge from the wood and be found mating and ovipositing again on freshly killed trees. Long-horned wood borers usually range from 1/2 to 1.5 inches in length, have antennae at least 1/2 as long as the body, and have long legs. Colors and particular markings vary greatly from species to species. Ash, oak, and hickory are among the most commonly attacked woods, however, any wood in the right condition may be attacked. When firewood is stored indoors where temperatures are high, it is not unusual for the adult beetles to emerge, even during mid-winter. Although they may become a nuisance pest by their presence, they do not attack finished or dried wood inside the home.


Long-horned beetle.

Long-horned beetle.


Locust borer on golden rod.

Locust borer on golden rod.


Flatheaded borers can also infest potential firewood. The larvae are similar in appearance and habits to the long-horned beetles. Tunnels made by the larvae are unique in that they are usually three times wider than high. Adults are flattened and somewhat elongate in shape with short antennae and legs. These beetles normally emerge during the summer months. They will not attack finished or dried wood. The bronze birch borer, one of the flatheaded wood borers, is occasionally found in homes where birch logs have been brought in for fireplace decoration.


Flat headed borer.

Flat headed borer.


A recently discovered pest of ash trees (Emerald Ash Borer) has the potential for serious destruction. Its spread into Indiana has been facilitated by the movement of firewood. For this and other reasons we recommend that firewood NOT be moved but rather used on site. For more information on the Emerald Ash Borer .


Emerald ash borer.

Emerald ash borer.


Emerald ash borer tunnel damage.

Emerald ash borer tunnel damage.


Bark beetles and ambrosia beetles are a large group of small beetles that may occasionally be found infesting firewood. Most are less than 1/8 inch in length and are brownish or black. These beetles and their larvae tunnel and make extensive galleries just under the bark of dead and dying trees. Bark beetles will not attack finished nor seasoned wood.


Tunnel diagram under the bark.

Tunnel diagram under the bark.


European bark beetle.

European bark beetle. (Photo Credit: Milan Zubrik, forestryimages.org)



Bark beetle galleries.

Bark beetle galleries.


Carpenter Ants

Firewood stacked on the ground for a long period of time or not allowed to dry out sufficiently can be subject to attack by carpenter ants. These large black or reddish ants may be up to 3/8 inch long. Bringing carpenter ant infested wood into the home generally will not spread the infestation inside the home. Only wood that is higher than normal in moisture content is susceptible to carpenter ant damage.


Carpenter ant.

Carpenter ant diagram.



Carpenter ant.

Carpenter ant.


TERMITES

Wood stacked on the ground can become infested with termites. Their presence is not usually noticed until the wood is moved during the summer or fall. Infested wood may have mud tunnels on the outside, or tunnels may be noticed if the wood is split. Termites may appear dormant during the winter months in these areas. Fire wood should not be treated with insecticides. Termites accidently brought indoors with firewood will not infest structural wood. Their presence in firewood, piled close to the home, may warrant a home inspection for termites, however.


Termite diagram.

Termite diagram.



Termites.

Termites.


MISCELLANEOUS PESTS

Many spiders, small beetles, wood roaches, sowbugs, pillbugs, wasps, ants and small flies may hide and/or overwinter in firewood. These pests generally leave the wood within a few days after being brought indoors. Most of them are harmless. Some beneficial wasps that emerge from wood are parasites of wood-boring insects. Horntails (large wasps 1-1/2 to 2 inches long) may infest trees that are dead or dying. These wasps are harmless and usually do not appear in large numbers.


Sowbug diagram.

Sowbug diagram.



Sowbug on wood.

Sowbug on wood.



Horntail.

Horntail


CONTROL AND PREVENTION

Homeowners must accept that nuisance insects will be brought into the home with firewood. After being warmed up they become active and may become nuisance pests. Recognizing them and knowing where they are coming from can reduce anxiety when homeowners discover these pests. Homeowners should not make a practice of applying chemicals to firewood for pest control because of the possibility of harmful fumes being produced when the wood is burned. When control of existing pests becomes necessary, however, surfaces can be sprayed with appropriately labeled synthetic pyrethroids to help reduce ants, spiders, and some other miscellaneous pests. There is little that can be done to protect wood from borers, and there are no practical controls for wood-boring larvae once they have entered the wood.

The following guidelines may be helpful in reducing firewood pests:

Purdue Extension Entomology, 901 W. State Street, West Lafayette, IN 47907, (765) 494-8761

Department of Entomology | College of Agriculture | Extension

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