Extension Communications 3614 Administrative Services Building Ames, Iowa 50011-3614 (515) 294-9915

10/13/03

Contacts:
Laura Jesse, Entomology, (515) 294-7400, lrhansen@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu

Yard and Garden Column for the Week Beginning Oct. 17, 2003

Managing Firewood Insects

By Laura Jesse
Extension Entomologist
Iowa State University

Picture this. It is the middle of winter and you are snuggled up in front of a crackling fire with a warm mug of hot chocolate in one hand and a garden catalog in the other. You are daydreaming of spring when, from out of nowhere, a large beetle buzzes past your head. How in the world did a huge beetle get into your house in the middle of winter? In all probability, you need look no farther than the stack of firewood next to your fireplace. In addition to warmth, firewood can sometimes bring these unexpected hitchhikers into our homes. Luckily, most of them pose no danger to us, our homes or our belongings.

There are a number reasons insects find your firewood attractive. They may be nesting in the wood, feeding on the wood or over-wintering under the bark. There are a couple of things you can do this fall and winter to minimize the number of insects entering your home from your firewood. First, stack firewood off of the ground. This aids in drying and makes it more difficult for insects to crawl into the woodpile. Second, leave firewood outside until a day or two before it will be burned. Insects in firewood stored outdoors will generally require a couple of days to warm up before becoming active.

We strongly advise against using insecticides on firewood. Treating firewood with insecticides has little benefit and is potentially dangerous. Most insecticides will not penetrate deep enough into wood to kill the insects. Additionally, storing and burning insecticide-treated firewood indoors could pose a health hazard, as the insecticide may be vaporized into the living area of your home.

There are several groups of beetles that feed on wood, which can accidentally be brought into your home in firewood. These insects can be a nuisance if they emerge from your firewood, but they will not harm the wood in your home. Longhorned beetles are attracted to dying, freshly cut or recently killed trees. They lay their eggs on the bark of the green wood. The larvae (commonly called roundheaded borers) emerge from the eggs, burrow into the tree and spend one to three years tunneling through the wood. These beetles get their name from their long antennae that are half as long, or longer, than their bodies. In Iowa, adult longhorned beetles commonly range from 1/2 to 1-1/2 inches in size. Many are attractively colored, often with yellow stripes on their bodies.

Metallic woodboring beetles are similar to longhorned beetles in that the larvae bore into wood, pupate and then can emerge as adults from firewood stored in homes. The larvae are called flatheaded borers because they appear to have a large, flattened head. These beetles have short antennae, are somewhat bullet shaped and have a metallic sheen.

Bark beetles often attack dead or dying trees, making them common in firewood cut from dead trees. These are small (less that 1/8 inch), brown or black and cylindrical beetles. The adult beetles tend to attack wood in groups, so a log cut from an infested tree can contain hundreds of individuals.

There are a wide variety of insects that over-winter under the bark of trees and in wood piles. When you warm this wood by bringing it into your home, these insects will wake up and come crawling out. Pillbugs, centipedes, millipedes and ground beetles are commonly found in firewood. None of these insects will harm you or your home. They need only be picked up and removed.

There are, however, two insects that may cause problems if you keep firewood stacked against your house - termites and carpenter ants. Termites may feed on wood that was stacked directly on the ground. While the main termite nest, which contains the queen, is in the ground below, termite workers can tunnel into the firewood where they feed on the wood's fiber. There may be mud tunnels visible on the outside of the wood and within the log itself. Termites brought into your home in firewood cannot establish a new nest and will not damage your home or your furniture.

Any wood that remains moist for an extended period of time becomes a likely candidate for infestation by carpenter ants. Carpenter ants do not feed on the wood. They merely hollow out galleries or nests in the wood. These galleries will be smooth and follow the grain of the wood. If infested firewood is brought into the house, the ants may warm up and move out of the wood. This can be an annoyance, but the odds of these ants establishing a nest in your house are very low.

As you are chopping firewood this fall, remember to stack it off of the ground and away from your home. Keep in mind that you will need to make frequent trips to the woodpile to avoid having firewood sit indoors too long. However, if you do get an unexpected insect guest this winter, don't worry. Just pick it up and remove it from your home.

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ml: isugarden

Editors: Two color photos, suitable for publication, are available at right. Click on each thumbnail photo to go to the fullsized photo. The top picture's fullsize photo is 76K and the bottom picture's fullsize photo is 96K. Caption: Two longhorned beetles that commonly emerge from firewood are the redheaded ash borer and the oak borer. Top photo is the Red Headed Ash Borer. Photos by Marlin Rice.

Caption: Oak Borer

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