When it comes to destroying wood, powderpost beetles come in second to termites. Wood that has been infested by these beetles is perforated with many tiny “shot holes,” about as small as a pencil lead. Material that is grated creates a flour-like substance to filter from the holes. When the wood is broken or cut, the inside of the infested wood may contain large quantities of the packed powder.
Powderpost beetles most often attack joists, sills, hardwood flooring, sub-flooring, and interior trim in buildings—typically in the South, where beetles prefer the warm, humid weather. They’ve also been known to enter the United States from more tropical places through ports in the South—and they end up in lumberyards where they can infest wood. Hickory furniture, implement handles and ladders are also favorable to powderpost beetles. The structural integrity of infested wood can eventually be highly diminished if infestations are not treated.
The powderpost beetle is of the subfamily Lyctinae, and there are 11 known lyctine species in both Canada and the United States. Adult powderpost beetles can fly and are drawn to light.
Powderpost Beetle Identification
The powerpost beetle is small—anywhere from 2 to 7.5 millimeters long. They range from brown to red-brown in color and can even be as dark as black. It has a body that is elongated and ever-so flattened. Its head stands out; there is no pronotum covering it. There are 11 segments in the antennae; the final two are widened into a terminal club. This is perhaps one of the beetle’s distinguishing features. The powderpost beetle looks much like the flour beetle, except flour beetles have a club with three segments instead of the powderpost beetle’s two.
Powderpost beetles eat the starchy part of the wood in which they dwell; they don’t eat lignin or cellulose because they are not able to produce cellulase. Therefore, sapwood is the extent of their diet. The adult powderpost beetles have two sets of wings.
Powderpost Beetle Habitat
Most of the year, adult powderpost beetles live in buildings, although they aren’t usually found until the weather turns warm as this is when they are most active. They can create a home in almost any product made of wood and also dwell in lumberyards.
Powderpost Beetle Life Cycle
Powderpost beetles leave infested wood from late in the winter through the early summer months. The females lay eggs in the pores of the wood during this time. The eggs hatch, and small curved grubs appear that eat into the wood and pack the holes with the fine, crushed wood. When they are completely grown, the grubs experience a pupal stage and then appear again as beetles. The beetles take anywhere from a few months to several years to finish one generation. The length depends on the species as well as on the wood’s starch substance.
Powderpost Beetle and Humans
Powderpost beetles live physically very close to humans. Because the beetles reside in wood items like furniture, they often move with people as they move from home to home. The beetles may infest one location, move within the furniture to another place, and then infest timber in their new environment.
Beetles can cause serious damage to wood products, of course including trees. The beetles like new wood, preferably only up to five years old. They can also infest bamboo. Most common infestations, however, are in new homes or wood products that are newly manufactured. Most likely, the wood became infested with eggs or larvae because the wood wasn’t appropriately stored or dried.
Powderpost beetles can be controlled by spraying or painting infested wood with one of these insecticides: permethrin, cypermethrin, and cyfluthrin (these would be the active ingredient listed on the label.) They are available as emulsifiable concentrates that can be watered down according to directions on the label.
For effective control, all surfaces receiving treatment must be thoroughly wetted. This will kill emerging powderpost beetle adults, as the insecticide will enter only somewhat into the wood. As such, the larvae will not be killed. Therefore, the best time of year to treat is springtime since pupae are leaving the wood at this time. It may be necessary to do several treatments. If fresh powder is visible about a week after treatment, the insecticide residues have dissolved, and another treatment is needed.
Of course treating hardwood floors and other finished surfaces should be done with care so as to prevent damaging the finish. If unsure, try treating a small, unseen area initially.
These beetles will not typically infest wood if it’s been finished or painted. But beetle larvae will mature and emerge as adults in finished wood. They’ll leave their mark—“shot holes”—on the wood’s surface. To kill infestations, wood products can be cooled to 0 degrees Fahrenheit for quite a few weeks or warmed for four hours at 150 degrees Fahrenheit. Of course one must be careful not to mar the wood during either the cooling or heating process.
If interested in having a professional tackle the problem, many pest control companies provide control services for powderpost beetles. Fumigation may be necessary if the problem is extensive in a structure or in areas that are difficult to treat. In these cases, professional pest control is necessary.
Taxonomy: The taxonomy of the powderpost beetle is as follows:
The powderpost beetle’s kingdom is Animalia and its phylum, Arthropoda. It comes from the Insecta class and the Coleoptera order. Bostrichoidea is the beetle’s b superfamily and Bostrichidae, its family.
Development and Reproductive Life Cycle: When eggs are laid, they are dropped in pores, cracks, crevices, tunnels, or in old holes in wood. The small larva hatches and nestles in the wood. It digs to the surface and pupates as it continues feeding and growing to maturity. The adult exits the pupa and continues the passageway to the wood’s exterior. Next, they leave, mate, and the females come back to lay eggs. This is often the first initial evidence of a powderpost beetle: exit holes and sawdust from exiting the wood. The beetle’s lifecycle can range anywhere from three months to more than two years, depending on the type and species of the beetle.
Feeding: Some species of powderpost beetles are particular about the types of wood they infest; some, on the other hand, are more general in their preferences. Typically, though, they are either hardwood or softwood, also known as conifer, feeders. When larva feed inside of wood, very fine excrement will flow from the wood’s exit holes at even the smallest movement.