Wood-boring beetles: in the house, in firewood or in your trees

The wood borers on this page

Powderpost Beetles Lyctinae (e.g., Lyctus brunneus, Lyctus planicollis) Powderpost beetles are small brown beetles whose larvae tunnel through dry, seasoned hardwood. Often the first clues are tiny round exit holes and little piles of flour-fine dust on floors, furniture or paneling. Deathwatch beetles Anobiinae Of the three groups of beetles that bore wood inside buildings, the deathwatch beetles are the ones a crawl space should worry about. True powderpost beetles stick to hardwood trim and furniture, but anobiids attack the spruce, pine, fir and Douglas-fir used for floor joists, studs, sills and beams, and because they digest cellulose rather than depending on the starch that fades from aging wood, they can keep reinfesting a house year after year. They need damp wood to do it, which is why Kentucky and NC State treat them as a moisture problem first and an insecticide problem second. Common Furniture Beetle Anobium punctatum The common furniture beetle, Anobium punctatum, is a small anobiid powderpost beetle, often called woodworm. Its larvae tunnel through seasoned wood for a year or more, and despite the name it also attacks floors, framing and structural timbers. Old House Borer Hylotrupes bajulus Despite its name, the old house borer most often turns up in fairly new buildings. Its larvae tunnel inside pine, spruce, fir and other softwood framing for years, and damp, poorly ventilated spaces let infestations spread. Horntails (Wood Wasps) Siricidae (e.g., Sirex areolatus, the western horntail) Horntails, also called wood wasps, develop inside dead or dying trees. When infested logs are milled into lumber, adults can chew their way out of the walls of a newly built home, but they can't sting and won't reinfest the building. Peachtree Borer Synanthedon exitiosa The peachtree borer is a native clearwing moth whose larvae bore into the lower trunk and roots of peach, cherry, plum, apricot and other Prunus trees. The first sign is usually a mass of gum mixed with sawdust at the base of the trunk. Flatheaded Appletree Borer Chrysobothris femorata The flatheaded appletree borer is a native metallic wood-boring beetle. Its larvae tunnel under the bark of the trunk and main branches of young, newly planted or stressed trees, apples and many shade trees alike, and can girdle and kill them. Emerald Ash Borer Agrilus planipennis The emerald ash borer is an invasive wood-boring beetle from Asia that has killed tens of millions of North American ash trees. Its larvae feed just under the bark, cutting off the flow of water and nutrients until the tree dies.

Where are the holes? That tells you which borer it is

Many different insects bore into wood: beetles, some moths and wood wasps. Only some of them can keep breeding in the wood of a house, so the first question is where you found the damage.^[8][1]

• Furniture, flooring, paneling, molding, window and door frames, plywood and bamboo items: powderpost, deathwatch or false powderpost beetles. Use the pen and frass tests below, then the powderpost beetle guide.^[1]
• Pine, fir or spruce framing, rafters and log walls: possibly the old house borer. It infests softwoods only and won't attack hardwoods such as oak, ash, maple or poplar.^[4][6]
• Firewood, or a beetle that turns up in a newly built house: likely a flatheaded or roundheaded borer, bark beetle or ambrosia beetle that came in with the wood. UC IPM says these typically won't attack wood structures or furniture. Wood wasps can emerge from new lumber too.^[1]
• Living trees and shrubs: tree borers. Colorado State lists holes in bark, galleries under the bark, oozing wounds on trunks and large branches, and canopy thinning as signs.^[8]

Powderpost, deathwatch or false powderpost? The pen and frass tests

UC IPM's two quick tests: push the tip of a click-type ballpoint pen into an exit hole and see how much fits, then rub some of the dust from the galleries between your fingers.^[1]

• Powderpost beetles attack hardwoods and bamboo with large pores and high starch content. Only the tip of a pen fits in the exit hole, and the frass feels like talcum powder.^[1][2]
• Deathwatch beetles mostly infest softwoods such as Douglas-fir, especially old or partly decayed wood with more than 14% moisture, so they're less of a problem in heated and air-conditioned homes. The pen tip and part of its angled face fit, and the frass feels gritty.^[1]
• False powderpost beetles infest floors, furniture and paneling; some bore through plaster and soft metal. The whole pen point usually fits, and the coarse frass is hard to dislodge.^[1]
• Life cycles range from about 3 months to more than a year for powderpost beetles and up to 20 years for one large species in hardwood flooring.^[1]
• Hole sizes from Kentucky: lyctid powderpost beetle holes are round and about the size of a pinhead, anobiid holes (the deathwatch group) are 1/16 to 1/8 inch, and bostrichid (false powderpost) holes are 1/8 to 1/4 inch. Penn State gives 1/16 to 1/8 inch for powderpost beetle holes.^[3][5][1]
• Deathwatch beetle holes can be of various sizes, while holes from powderpost or false powderpost beetles tend to all be the same size.^[1]
• Sources give different life spans inside the wood: UC IPM says about 3 months to more than a year for powderpost beetles, while Kentucky says larvae emerge as adults one to five years after the eggs hatch.^[1][3]

Beetle damage or termites?

Fine powderpost frass is different from the larger, granular, almost pepperlike pellets drywood termites leave; look closely and termite pellets have ridges on their sides.^[1]

Kentucky notes that powderpost beetles are sometimes confused with flour beetles, drugstore and cigarette beetles, weevils and other small beetles that infest stored food. Those belong in the pantry, not in the wood.^[3]

• Perfectly round holes about one-half inch wide in outdoor wood such as siding, eaves, window trim, fascia boards and decks, with fine sawdust on the ground below, are the work of carpenter bees, not beetles; see the carpenter bee guide.^[10]

Is it still active?

Holes alone don't prove live beetles. With false powderpost (bostrichid) beetles, Kentucky says the holes females bore to lay eggs are empty of powder, while holes made by beetles that finished developing are packed with it. Small numbers of beetles can keep emerging from wood for up to about five years.^[3]

Penn State says many powderpost beetles will keep breeding in the same infested piece of wood for generations. The powderpost beetle guide covers how to tell active damage from old damage before you treat.^[5]

• Kentucky says moisture meters, which pest control firms use, help predict whether wood is likely to be infested again.^[3][4]

Oval holes in pine framing: the old house borer

The old house borer is a black to gray beetle with long antennae whose larvae tunnel in pine, spruce and other softwoods, weakening structural timbers. Despite the name, Penn State says many infestations are noticed in homes just four to seven years after construction, and Kentucky says they are most common in structures less than about 10 years old.^[6][4]

• Signs: oval emergence holes, about 1/4 inch according to Penn State and 1/4 to 3/8 inch according to Kentucky, and tunnels with sculptured walls and barrel-shaped frass.^[6][4]
• Sound: the larvae make a rasping or clicking sound as they chew, and Kentucky says it can often be heard through walls, floors and ceilings once larvae are fully grown.^[6][4]
• Time in the wood: Kentucky gives an average of about 3 to 6 years, sometimes as little as 2 and sometimes 10 years or longer; Penn State gives three to fifteen years, with five to seven typical in heated Pennsylvania structures.^[4][6]
• Moisture drives it. Kentucky says larvae do best at 15 to 25 percent wood moisture and are unlikely to survive below 10 percent, so dry, climate-controlled, well-ventilated structures usually see little damage.^[4]
• It is a pest of buildings and lumber only. Kentucky says it does not infest living trees, stumps or firewood, and that hardwood flooring, cabinetry and furniture are generally immune.^[4]
• Penn State calls fumigation the only absolute way to eliminate an infestation in a structure, but it is expensive, must be done by licensed professionals and gives no lasting protection. Borate surface sprays keep newly hatched larvae from entering bare wood but don't work on varnished, waxed or sealed wood.^[6]

Beetles from firewood and new lumber

Flatheaded and roundheaded borers, bark beetles and ambrosia beetles are forest insects that start their life cycles in declining trees. They can arrive in firewood, or emerge from wood used in a new building because they were already in the tree when it was milled, but they can't reinfest the wood in the structure.^[1]

• Wood wasps (horntails) can also emerge from infested wood used in new buildings. Colorado State says they leave circular exit holes about the diameter of a pencil and don't sting.^[1][8]
• Kentucky warns that correct diagnosis matters, because many beetles found with firewood are not the old house borer.^[4]
• Bring in only the firewood you will burn that day. To kill beetles already in a woodpile and keep new ones out, UC IPM suggests sealing it under thick (10 mil) clear plastic in a sunny spot for several months.^[1][9]
• Don't move firewood. That is one of UC IPM's quick tips for bark beetles.^[9]

Borers in living trees

Tree borers include beetles (flatheaded, roundheaded and bark beetles, and some weevils), clearwing and other moths, and horntails. Most attack trees already stressed by drought, injury or disease, though aggressive invaders such as emerald ash borer can kill healthy trees.^[8][9]

For peaches, cherries, plums, apples and other fruit trees, the peachtree and fruit tree borer guide covers inspection, digging out larvae, nematodes and trunk spray timing.^[7][11]

• Flatheaded (metallic) borers: adults leave D-shaped exit holes, and the larvae make meandering mines under the bark. Emerald ash borer and the flatheaded appletree borer are in this group.^[8]
• Roundheaded (longhorned) borers: larvae often push coarse, stringy sawdust out of the bark, and adults chew oval exit holes.^[8]
• Clearwing borers are moths, not beetles. They make gouging wounds, often in the upper root crown, and the empty pupal case is often left sticking out of the exit hole.^[8]
• On peach and other stone fruit trees, one of the first signs of peachtree borer is a mass of gum around the base of the trunk, from about three inches below to 12 inches above the soil, often mixed with sawdust and frass.^[7]
• Bark beetles: pitch tubes (blobs of sap mixed with boring dust) on pine trunks, piles of dry boring dust on the bark, or a buckshot pattern of tiny holes where shothole borers emerged. Pines and firs have their own guide.^[9]
• On apple trees, UNH says strings of fine frass being pushed out of the wood mean an active borer, and that weakened, stressed or strongly leaning trees are attacked most often.^[11]

Protecting trees from borers

• Keep trees healthy: choose trees suited to the site, remove damaged or overshaded limbs, and water adequately.^[8][9]
• During drought, UC IPM suggests watering trees deeply but infrequently, such as twice a month, so water reaches about 1 foot into the soil, rather than frequent shallow lawn-style watering.^[9]
• Prune out infested limbs and remove dying trees so borers don't emerge and attack nearby trees. Trees that are seriously infested or already dying from beetle attacks can't be saved with insecticides.^[9]
• Insecticides have a place when many weakened trees nearby are building up borer numbers; then protecting healthy neighboring trees may be warranted. UC IPM adds that preventive sprays are no substitute for proper care.^[8][9]
• Avoid wounding the bark at the base of fruit trees and don't pile mulch against the trunk.^[7]

Treatment options for wood in the house

This is a short version; the powderpost beetle guide covers each method in detail, including moisture control, floors and furniture.^[1]

• Borate products applied by a licensed pest control operator must penetrate the wood to kill larvae; penetration is better in moist wood and may reach only the top 1/4 inch if moisture is under 15%.^[1]
• For extensive infestations or inaccessible structural wood, professionals offer whole-building fumigation, but it doesn't prevent reinfestation once the gas is gone.^[1]
• Wood-boring beetles are hard to control once established, so prevention matters most.^[1]
• Remove and replace infested structural wood when you can, and burn it or take it to a landfill.^[1]
• Fumigation works best on adults and larvae; the eggs need a higher dose of fumigant.^[1]
• Borates applied to bare wood last indefinitely as long as the wood stays dry and the borate isn't leached out by water.^[6]

Prevention

• Inspect furniture, lumber and other wood items before bringing them in; remove and fumigate items that show signs of beetles.^[1]
• Bring in only as much firewood as you'll burn that day.^[1]
• Remove dead tree limbs and scrap lumber near buildings.^[1]
• Watch for new exit holes and beetles collecting on windowsills; tap frass out of galleries to help identify the pest.^[1]
• Inspect building materials before use. Kiln drying lumber kills beetles already in it but doesn't prevent reinfestation later.^[1][6]
• Sanded and varnished wood is not normally attacked by old house borers, because the females can't find crevices to lay eggs in.^[6]
• If you buy an item with many holes, such as an antique, Penn State suggests asking the dealer for a receipt from the company that fumigated it.^[5]

Common questions

Can beetles from my firewood infest the house?

Usually not. UC IPM says the flatheaded and roundheaded borers, bark beetles and ambrosia beetles that come in with firewood won't attack wood structures or furniture. Powderpost beetles can arrive in firewood, but Kentucky says that is seldom why other things in a home become infested.^[1][3]

Will the borers in my tree spread to my house?

Tree borers such as flatheaded and roundheaded borers and bark beetles are forest insects that UC IPM says typically won't attack wood structures or furniture. The reverse is also true for the old house borer, which Kentucky says does not infest living trees.^[1][4]

What is the tapping or clicking sound in my walls?

Deathwatch beetle adults tap their heads against wood, usually at night, probably to find mates. Old house borer larvae make a rasping or clicking sound as they chew, which can often be heard through walls, floors and ceilings.^[1][6][4]

Do I need to fumigate the whole house?

Only for extensive infestations or structural wood you can't reach, according to UC IPM. Small items can be heated or frozen, bare wood can be treated with borates by a licensed applicator, and infested pieces can be replaced. Fumigation doesn't prevent reinfestation.^[1][6]

Sources

1. University of California Statewide IPM Program, “Wood-Boring Beetles in Homes (Pest Notes, Home and Landscape).” ipm.ucanr.edu/home-and-landscape/wood-boring-beetles-in-homes/ (accessed 2026-10-06)
2. NC State Extension, “Powderpost Beetles and Wood-Inhabiting Fungi.” content.ces.ncsu.edu/powderpost-beetles-and-wood-inhabiting-fungi (accessed 2026-10-19)
3. University of Kentucky Entomology, “Powderpost Beetles (ENTFACT-616).” entomology.mgcafe.uky.edu/ef616 (accessed 2026-11-10)
4. University of Kentucky Entomology, “Old House Borer (ENTFACT-653).” entomology.mgcafe.uky.edu/ef653 (accessed 2026-11-10)
5. Penn State Extension, “Powderpost Beetles.” extension.psu.edu/powderpost-beetles (accessed 2026-11-10)
6. Penn State Extension, “Old House Borer.” extension.psu.edu/old-house-borer (accessed 2026-11-10)
7. Penn State Extension, “Peachtree Borer.” extension.psu.edu/peachtree-borer (accessed 2026-11-10)
8. Colorado State University, Department of Agricultural Biology, “Shade tree borers.” agsci.colostate.edu/agbio/ipm-pests/shade-tree-borers/ (accessed 2026-11-10)
9. University of California Statewide IPM Program, “Pest Notes: Bark Beetles (Publication 7421).” ipm.ucanr.edu/PMG/PESTNOTES/pn7421.html (accessed 2026-11-10)
10. Clemson Cooperative Extension, Home & Garden Information Center, “Carpenter Bees (HGIC 2407).” hgic.clemson.edu/factsheet/carpenter-bees/ (accessed 2026-11-10)
11. UNH Cooperative Extension, “Borers in New Hampshire Apple Trees (fact sheet).” extension.unh.edu/resource/borers-new-hampshire-apple-trees-fact-sheet-0 (accessed 2026-11-10)