Manage the Risk of Insect Pests in Firewood
 | Author:
Allison Kosto, MSU Broadwater County Extension Agent
MSU Broadwater County Extension Agent |
Allison Kosto
MSU Broadwater County Extension Agent
Have you ever heard of the emerald ash borer? It’s a wood-boring insect that is responsible for causing billions of dollars of damage across the United States and wiping out entire populations of ash trees. While the emerald ash borer is currently not in Montana, it is a real threat. The borer has primarily spread across the United States through firewood. Unfortunately, the emerald ash borer isn’t the only insect that you might transport with firewood.
Insects associated with firewood are typically grouped into two categories: Those seeking shelter in wood and those feeding on wood. There are many insects that seek shelter in wood for the winter. Some of these insects could be on the wood before it's cut, while others may find it after it’s been stacked. They often nestle in loose bark, tree crevasses or hollow trunks. Insects could include beetles, spiders, ants, pill bugs, wasps, flies and more. Sometimes you’ll also find spider egg sacks and moth cocoons. Most of these insects are harmless.
Insects feeding on wood are often more of a concern, but the good news is that they are unlikely to cause harm to your home. Wood feeding insects are most likely to attack trees that are already dead or dying. They are unlikely to harm healthy trees or dry wood. There are several types of insects to watch for.
Wood-boring beetles are the most common. The emerald ash borer is one example but there are many others. They lay eggs in the wood while it is still green. The larvae tunnel and feed on the wood for a year or more before they pupate. The adults then emerge and seek another freshly killed or dying tree to lay its eggs. If these insects exist, they will be in the wood when you cut it and they could emerge when stacked, especially if it’s indoors, where it’s warmer. It’s often difficult to tell if there are wood-boring beetles in the tree prior to cutting it unless you can find entrance and exit holes. The good news is that they are unlikely to cause harm to your home because they will not attack finished or dried wood.
Bark beetles are slightly different than wood borers. Rather than bore directly into the wood, bark beetles tunnel under the bark of the tree, making extensive weblike galleries. If you peel off the bark, you will see evidence of their damage. However, just like wood-boring beetles, they attack trees that are already dead or dying. They are also unlikely to cause damage to your home.
Carpenter ants are another common insect. Infestation of carpenter ants typically happens after the firewood is stacked, as they will only utilize dead wood. Contrary to the previously mentioned insects, carpenter ants don’t actually eat the wood. Instead, they simply use it for their nests. Carpenter ants prefer wood that has a small amount of moisture and that is already partially soft or rotting. Therefore, it is also unlikely that they will do any damage to your home. The ants will search for a suitable site even if they can’t find one and can be a nuisance if they are inside your home.
Termites are also often an insect of concern. There are a few pockets of termites in Montana, primarily in urban areas. It is unlikely that you will find termites in native trees and in general, the risk of termite invasion in Montana is much lower than in some other states.
There are strategies to manage, eliminate or reduce insect pests in firewood. The most serious risk is moving insect pests like the emerald ash borer to Montana through firewood. To avoid this, use only local firewood. Do not purchase firewood out of state or transport it here. If you are camping in another state, leave the firewood there. Be cautious of buying bundled firewood at stores and make sure that it’s from in-state.
Once you get firewood home, avoid stacking wood directly on the ground if possible. This will reduce moisture, making it less attractive to carpenter ants and it will burn better. Also, do not stack the wood against your house. Use the oldest wood first, as it’s more likely to be infested. Keep the wood undercover to keep it drier and reduce exposure. Shake the wood outside before you bring it into the house to dislodge any pests. Just bring in small amounts of wood at one time, usually enough for a day or two. The longer the wood is in the house, the greater the likelihood that pests will emerge. It is not recommended to treat firewood with pesticides. It is unnecessary and can be dangerous due to the fumes produced when the insecticides burn.
If you find unwanted guests in your house from firewood, simply sweep them up and throw them out. If you are concerned about the insect and need assistance identifying it, bring it to MSU Extension in Broadwater County at 416 Broadway in Townsend. You can also contact at 406-266-9242 or allison.kosto@montana.edu.
