Firewood and Insects

Pest Management Fact Sheet #5019

James F. Dill, Pest Management Specialist
Clay A. Kirby, Insect Diagnostician

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Introduction

Most of the insects that travel into homes on firewood create only a minor nuisance. Many insects, including flies, mosquitoes, wasps and earwigs, overwinter in spaces in and under bark of logs. Some insect-like animals, such as sowbugs, millipedes and spiders also “hitchhike” a ride on firewood. These hitchhikers can include gypsy moth eggs; hatching larvae create a nuisance. Other insects, such as bark beetles, infest firewood by living under the bark or boring into the wood. The trouble starts when the warmth of indoors signals that it is time to begin spring activities.

: Bark Beetle and Larva

: Black Carpenter Ant (wingless queen)

: Powderpost Beetle

Description & Biology

Carpenter ants are usually nocturnal but can be seen in the daytime when searching for food or water, or when a colony is overcrowded. Carpenter ants tunnel into wood to increase their nesting space. The queen starts a new colony in unsound, wet wood. Even though carpenter ants that come into homes in firewood are primarily nuisance pests, they may cause structural damage if a new nest is established in the timbers of a home.

Beetles that infest living or freshly-cut trees do not infest dead trees or dry wood. However, they can become a nuisance in homes when they emerge from firewood. The ideal way to avoid these insects is to cut living hardwood trees in the fall or early spring when the insects are in the overwintering or inactive developmental stage. The insects are attracted primarily to the scent of freshly-cut trees; therefore, trees cut in the summer are much more likely to be infested.

There are three families of powderpost beetles (Lyctidae, Anobiidae, and Bostrichidae) that can enter homes on firewood. These insects may infest the structures of homes, wooden tool handles, furniture, etc. Their presence is usually signaled by flour-like wood dust found below small holes in wood.

In general, firewood from dead trees is more likely to be infested with potentially destructive insects. Wood with the bark attached is also more attractive to wood-destroying insects. Many insects attack only wood with bark.

Management

The sooner the firewood is split, the quicker it dries, and the less attractive it is to most insects. Wood not split or wood left outside without covering is likely to become infested. The best place to store firewood is in the woodshed. Wood should be kept off the ground and protected from rain and snow. Air movement through a woodpile aids in its drying.

Poorly-vented basements should not be used to store firewood, especially wood that is not seasoned and dried. Inadequately-dried wood can become moldy, cause unpleasant odors and harbor insects. Humidity released from the wood can also cause mold or rot on structural materials in the basement.

It is best to move no more than a two-week supply of firewood into the home at a time to reduce the chance of insects becoming active. This is especially true with firewood from dead trees. The woodbox should be emptied and cleaned every two weeks.

FIREWOOD SHOULD NOT BE TREATED WITH INSECTICIDES!

When Using Pesticides

ALWAYS FOLLOW LABEL DIRECTIONS!

Pest Management Unit
Cooperative Extension Diagnostic and Research Laboratory
17 Godfrey Drive, Orono, ME 04473
1.800.287.0279 (in Maine)

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