You move a wooden chair or open the drawer of an old cabinet and find under it a small pile of fine powder that looks like flour, and on the wood surface small round holes as if made by a needle. This is the sign of woodworm, the name people give to the larvae of a group of small beetles that live inside wood for years and turn it into powder from the inside. In this article we show you how to read the signs, how to tell the beetle type from the size of the hole, and when freezing is enough and when you need a bigger treatment.
And the first question to ask is not "which pesticide is right?" but: is the infestation still active, or are these old holes from years ago? Many antique pieces carry holes from an infestation that ended long ago, and treating them today wastes money. On the other hand, a newer piece that drops powder every week may spread the problem to other pieces in the house.
Scientific name: Wood-boring beetle larvae from three families: Lyctinae, Bostrichidae, and Anobiidae.
Size and color: Adult beetles are small, from about 1 mm to 6 mm depending on the family; the damage shows as round holes and fine powder.
Where it lives: Inside raw, unfinished wood and in old or new wooden furniture.
How dangerous: It does not harm people directly, but it can make furniture brittle and may weaken structural timber after years.
Best time to control: When fresh powder appears under the holes, preferably before the beetles emerge in spring and summer.
What Happens Inside the Wood?
The adult beetle hardly eats wood at all; its job is to lay eggs. The female lays them in the pores and cracks of the wood, or digs a small pit for them, and she chooses raw, unfinished wood.
The larvae hatch and go deep, boring winding tunnels as they feed, and they stay there from several months to several years depending on the species and the wood. Finally they pupate near the surface, and the adult beetle emerges from a new round hole, pushing out with it or after it part of the powder accumulated in the tunnels.
This means the holes you see are exit holes, not entry holes, and that the real damage happened long before you saw them. The beetles themselves are rarely seen because they are small, short-lived, and active at night, and they usually emerge in spring and summer.
From Hole Size and Powder Feel: Which Beetle Do You Have?
Woodworm covers three main families, each with its preferred wood and distinguishing signs, and knowing the type tells you whether the infestation renews itself or dies out on its own.
True Powderpost Beetles (Lyctinae)
- Hole: Very small and round, about the diameter of a pinhead, roughly 1 to 1.5 mm.
- Powder: Very fine like flour or talcum powder, flows easily and piles up beside the holes.
- Wood: Hardwoods only, such as oak, walnut, cherry, and tropical hardwoods, and also bamboo. Their larvae need the starch found in the pale outer sapwood, so they do not attack pine and softwoods, and they prefer new, starch-rich wood.
- Where it appears: New furniture, wooden floors, doors and frames, imported antiques and carvings, and bamboo baskets.
- Cycle: Usually under a year in new wood, and the female lays from 10 to 50 eggs.
False Powderpost Beetles (Bostrichidae)
- Hole: Clearly larger, roughly 3 to 6 mm.
- Powder: Coarse like semolina, packed tightly inside the tunnels.
- Beetle: Cylindrical, brown to black, with the head bent down under the chest as if under a hood.
- Wood: New hardwood that still has starch and moisture, and tropical woods and bamboo; infestation often starts in the country of origin before shipping.
- Good news: They rarely reinfest the same wood after the first generation emerges, because the wood dries out inside the home.
Furniture Beetles (Anobiidae)
- Hole: Between 1.5 and 3 mm.
- Powder: Granular and gritty, with tiny pellets you can feel between your fingers.
- Wood: Both hardwood and softwood, including structural timber and beams, and they attack old wood too because they digest cellulose and do not depend on starch.
- Key requirement: Moisture. Their larvae need wood with moisture above about 13 percent, so they spread in damp places such as ground-level storerooms, basements, and unconditioned annexes, and rarely succeed in dry air-conditioned rooms.
- Cycle: Slow, often two to three years, and they reinfest the same wood generation after generation as long as the moisture is suitable.
The drugstore beetle and cigarette beetle come from this same family, but they do not eat wood; they infest spices, dried herbs, flour, and kitchen stores. If you find small, rounded brown beetles near food rather than near furniture, read our guide to grain weevils and stored-product pests.
There is also a simple test used by some university extension guides: insert the tip of a ballpoint pen into the hole. If only the thin tip goes in, it is probably a true powderpost beetle, and if part of the sloping cone of the tip goes in, it is most likely a furniture beetle. Holes clearly wider than that, packed with tightly pressed powder, point to false powderpost beetles.
Is It Woodworm or Termites?
Confusing the two is costly, because termites need a completely different treatment:
- Woodworm: Leaves clean round holes on the surface and fine or granular powder.
- Subterranean termites: Leave mud tubes on walls and foundations and eat the wood from the inside, leaving galleries full of soil, with no round exit holes.
- Drywood termites: Termites living in dry wood push out hard, uniform pellets, each with six sides, resembling poppy seeds or coarse sand, not powder.
- Winged swarms: Swarms of winged insects that emerge all at once and leave their wings near windows are a sign of termites, not woodworm.
There are also very small beetles that appear in new or damp homes and feed only on surface mold and do not harm wood. So do not judge an infestation from seeing a beetle alone; judge it from the holes and the powder.
Is the Infestation Active? Test Before You Treat
Before spending on any treatment, make sure the wood actually contains live larvae. Holes alone are not enough to judge. Signs of an active infestation:
- Powder: Light powder the color of freshly cut wood that returns after cleaning.
- Holes: Holes with sharp, clean edges and pale interiors, while the wood around them is old or finished.
- Finished wood: New holes that broke through the finish, with no trace of stain inside.
Signs of an old, finished infestation: yellowed, clumped, or dusty powder, and holes with dark edges matching the color of the wood surface. Note that moving or vibrating the piece may shake old powder out of the tunnels and give the false impression of activity.
The decisive test: vacuum up all the powder, seal existing holes with wax or wood filler or mark them with a pen, then place black paper under the piece and watch. New powder or new holes in the following months mean an active infestation. Because emergence peaks in spring and summer, you may need to wait until the next season to be sure.
The reassuring part is that woodworm is very slow compared to termites. Damage builds up over years, so waiting to confirm before treating is a sound decision in most furniture cases, unless the piece is valuable or powder is falling from it heavily.
Treating an Infested Piece of Furniture
The treatment method depends on the size and value of the piece and the type of beetle. But the first step is always the same: isolate the piece.
Move the infested piece away from other wooden furniture, especially raw, unfinished wood. If it is small, wrap it in plastic sheeting until you decide on a treatment, since emerging adults may lay eggs in another piece.
Freezing for Small and Medium Pieces
Extreme cold kills all stages inside the wood, including eggs, without any chemicals:
- Wrapping: Wrap the piece in a cloth or sheet, then place it in a thick plastic bag and seal it with tape after pressing out as much air as possible.
- Freezing: Place it in a freezer at minus 18 to minus 20 degrees Celsius (0 to minus 4 F) for 3 to 7 days depending on the thickness of the wood; frames and thin carvings need the minimum and thick pieces need a week.
- Rewarming: Take it out and leave it in the bag until it returns gradually to room temperature, which may take 24 hours for large pieces, so that the water condenses on the bag and not on the wood.
Freezing rarely harms wood, veneer, or finishes, but inlays of mother-of-pearl or ivory may be affected, so consult a specialist before freezing valuable antiques. Large pieces that do not fit a home freezer can be placed in a commercial cold room.
Heat and Replacement
If freezing does not suit the piece, there are two other options:
- Heat: Raising the core temperature of the wood to between 50 and 57 degrees Celsius (122 to 135 F) kills larvae and eggs, and treatment in specialized heating chambers may take up to 24 hours depending on the thickness of the piece. Exposing furniture to the sun does not raise the temperature deep in the wood enough, and may crack the wood and damage the finish.
- Replacement: If the infestation is in a board, a leg, or a part that can be taken apart, replacing it along with its neighbors is the fastest and surest solution, especially with both kinds of powderpost beetles because they rarely reinfest inside the home.
And if you are going to resand and refinish a wooden floor, wait a few months after treatment to make sure no new holes appear.
Surface Pesticide Treatment
Surface pesticides do not penetrate deep into the wood to reach distant larvae, but they have an important role: they kill adults the moment they emerge from the holes before they mate and lay eggs, kill larvae close to the surface, and prevent new eggs on raw wood.
So we use them on unfinished surfaces: the backs of cabinets, the undersides of drawers and chairs, inner frames, and beams in storerooms. Painted or varnished wood does not absorb pesticide, and for it, sealing the holes after treatment is enough.
In buildings where furniture beetles have reached the beams, ceilings, and floors, professionals turn to borate compounds that penetrate raw wood and last for years, or to full fumigation of the building or of furniture inside sealed chambers. This work is done by a licensed professional, and an engineer may be needed to assess the safety of structural timber.
Products We Recommend for Surface Treatment
At Orkida we rely on two long-residual pesticides for surface treatment, choosing between them by location: storerooms and raw timber, or furniture inside the home:
- Demon Max by Syngenta: Cypermethrin 25.3% emulsifiable concentrate, from the pyrethroids traditionally used in treating timber against beetles, with a long residual effect on the surface. We use it to spray raw timber in storerooms and annexes, beams, and the backs and undersides of furniture, at the label dose, covering the surface until the wood absorbs it. Because it is a solvent-based formulation, test it first on a hidden spot before applying near any finished surface.
- K-Othrine Partix by Envu (formerly Bayer): Deltamethrin 2.45% in a water-based suspension that clings to surfaces and whose effect lasts for many weeks, a period that covers the spring and summer emergence season. We prefer it inside the home on raw parts of furniture, shelves, and frames because it is water-based and lighter on the space, at the label dose, and we repeat the treatment if beetles keep emerging.
The rule we recommend with any pesticide: follow the label dose as written, spray with the space ventilated and free of children and pets, and do not return items to the cabinet until the spray is completely dry.
How Do I Keep Woodworm Out of My Home?
Most woodworm infestations enter the home with an infested piece, or find damp raw wood to start in. Prevention rests on these habits:
- Inspect before you buy: Used furniture, antiques, bamboo baskets, imported carvings, and old decorative timber are among the commonest sources of infestation. Turn the piece over and look at its back and underside, and look for sharp-edged holes and fresh powder.
- Beware of reclaimed wood: Old barn boards, wooden pallets, and demolition timber may carry live larvae, so freeze or treat them before using them for decor.
- Finish raw wood: The female lays her eggs in untreated wood, and varnish, paint, and wax close the pores and prevent it. Finish the exposed parts of furniture, including the back and underside.
- Seal old holes: After confirming the infestation has ended, fill the holes with wax or wood filler. An open hole is an ideal place for new eggs, and sealing it lets you spot any new hole later.
- Control humidity: Furniture beetles do not live in dry wood. Ventilate ground-level storerooms, fix water leaks, and do not store wooden furniture in a damp place or touching the ground.
To learn more about other household pests, browse the Pest Library.
Frequently Asked Questions
Does woodworm spread from one piece of furniture to another?
Yes, adult beetles fly and lay their eggs in any raw wood nearby. But the greatest risk is to unfinished wood, while well-finished furniture is rarely reinfested.
Do small holes in old furniture mean it is infested now?
Not necessarily. Many holes are old, from an infestation that ended years ago. Look for fresh light powder that returns after cleaning, or new sharp-edged holes, before deciding on treatment.
How long does woodworm live inside the wood?
It varies by type: powderpost beetles often complete their cycle in under a year in new wood, furniture beetle larvae remain two to three years or more, and some beetles may keep emerging from old wood for several years.
Is it enough to spray pesticide on the surface of finished furniture?
No. The finish prevents the pesticide from reaching the wood, and a surface pesticide does not reach the larvae deep inside anyway. Finished pieces suit freezing or heat treatment, followed by sealing the holes.
Does woodworm weaken furniture or ceilings?
In furniture, severely infested parts can become brittle and break. In buildings, furniture beetles may weaken beams in damp places after many years, which is why infested structural timber is checked by tapping and probing, and a specialist is consulted when in doubt.
Why did holes appear in new furniture I bought months ago?
Because the infestation was usually already in the wood before manufacture or shipping, especially in tropical hardwoods and bamboo. The larvae were inside the wood and the adults emerged in your home. Contact the seller, and treat the piece by freezing or replacement depending on its size.
To tell woodworm apart from the termites that feed on wood, see the termite guide and the carpenter ant article, and for other stored-product pests see the grain weevils and stored-product pests article.