From the scrap lumber in your backyard to the antique furniture in your living room, any older wood can fall prey to powderpost beetles. The larvae of these beetles break down wood by creating holes as they eat away at the wood after they hatch.
Powderpost beetles are bad enough outdoors, but when they find their way into your home, they can destroy your furniture or even your rafters, joists, and other parts of your home’s wood structure. Because they work quietly, slowly, and often in hidden areas, they can go unnoticed for years. While an infestation isn’t an emergency, it’s still worth addressing quickly.
Spot the Signs of Infestation
Powderpost beetles usually attack oak, walnut, and other hardwoods and prefer dry, seasoned wood. When they get into the house, it’s usually because they were brought in on an infested piece of firewood or old furniture.
The most obvious sign of their presence is the 1/16- to 1/8-inch round holes they leave when exiting the wood as adults. In an active infestation, you might also notice the sawdust (frass) they leave behind, which is a fine powder the consistency of flour and the color of fresh sawdust. This sometimes forms lines down the side of the infested piece of wood, but often just accumulates somewhere below the holes.
If you find no sawdust at all or only small amounts of darker, old sawdust, the infestation is most likely old, and you don’t have to treat for it.
The adults are 1/4-inch brown beetles with narrow bodies that typically emerge from the wood between April to July.
This is in contrast to another common boring beetle, the deathwatch beetle, which prefers softwoods and leaves behind a coarser sawdust. If you’re not sure which type of beetle you have, consult a pest management professional.
Getting Rid of Powderpost Beetles
If the infestation you’re dealing with is in rough-cut lumber, the solution is simple: take the lumber to a sawmill and have it kiln dried. This will kill the beetle eggs, larvae, and adults.
To treat small wood items, place the item in the freezer at zero degrees Fahrenheit for at least 72 hours. This will get rid of the larvae and adults, but some eggs might still survive, so occasionally check the item for damage over the next year.
Getting rid of these beetles on wood items in your home or in your home’s wood structure is a little more complicated, but pesticides containing borates can help. These are usually available as liquids or as a powder to be mixed with water. They’re designed to be simply sprayed or brush-coated onto the infested wood.
If you decide to apply pesticide yourself, make sure you treat the entire affected area. When an infestation spreads, it usually moves upwards, so inspect the space above the area that’s obviously infected and treat there, too, if needed.
Keep in mind, though, that if the infestation is inside paneled or plastered walls, or some other place that’s hard to reach, it’s difficult to apply the pesticide thoroughly enough to get the job done. In this case, it’s worth calling in a professional.
Because the powderpost beetle’s life cycle ranges from three months to a year, you might need several applications of pesticide to get rid of the beetle population completely.
On very dry wood, the pesticide might not be able to penetrate deeply enough to reach larvae already within the wood. Spraying the wood with water before you apply the pesticide can help, but you might still need to re-treat the wood three to six months later.
For an infestation that hasn’t responded to several applications of common borate pesticides, fumigation is the next step. This process involves powerful pesticides available only to professionals. It’s highly effective and won’t damage antique furniture or other delicate wood items. In fact, it doesn’t even leave a residue. Smaller items can be placed in a fumigation chamber.
If part of your house is infested, a pest controller can bring in equipment to fumigate the area, but you’ll need to leave the house for several days. While fumigation will get rid of postpowder beetles at any stage of development, it won’t prevent future attacks.
Keep Them from Coming Back
If you buy rough-cut lumber, it should be kiln-dried to kill all stages of the beetle. For finished wood items, sanding and varnishing the wood makes it less unappealing to the beetles because it eliminates the tiny crevices they need to lay their eggs.
For an item has been exposed to powderpost beetles, but not yet infested, spraying it with a borate-based pesticide will keep any larvae that appear from boring into the wood. This won’t work on wood that’s been waxed or varnished, though, because the pesticide won’t soak in.
Don’t store wood furniture or other items in a wooden barn, shed or other outbuilding. These buildings often harbor beetles and other insects that will quickly find their way to your valuable item.
If you buy a piece of wood furniture or decor with holes that look like the work of postpowder beetles, request proof from the seller that the item has been fumigated. If plan to use wood that’s been stored outdoors for a DIY project, make sure it’s free of beetles or at least sand then varnish or paint the wood.
While postpowder beetles can do a lot of damage if left unchecked, they’re usually not difficult to get rid of. Most common borate-based pesticides will do the trick. Their long life cycle means it takes years for serious damage to occur, but the earlier you act when you notice the tell-tale round holes, the less risk there is the infestation will spread.