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Wood-destroying Beetles
by Barb Ogg, PhD, Extension Educator

Wood-destroying Beetle Life Cycle

The larval or grub stage, in which the
wood-destroying beetles do their damage, is
long in proportion to the rest of the life cycle

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There are a number of small beetles that attack wood. Most attack wood that is alive (i.e., trees) or green lumber,) but a few will attack seasoned wood, like furniture, flooring, paneling, and stored lumber. Sapwood, the newly formed outer wood, is higher in nutrients and is attacked more frequently than heartwood.

Although losses are heaviest in warm, humid climates of southern states, some of these insects occur throughout the entire U.S. Ongoing problems with powderpost beetles are uncommon in Nebraska, and chemical treatment is seldom necessary.

The damage is done by the larvae that feed and reduce the wood to a fine powder or mass of small pellets. Scientists call this debris frass. The larvae can tunnel in the wood for months or years before they emerge as adult beetles. Since the larvae never come to the surface, the damage can be considerable before it is noticed.

How can you tell if beetles are present? If you see piles of very fine sawdust on or beneath wood, look for small round or oval "shotholes" in the wood surface. These are exit holes and indicate that some of the larvae have transformed to adults and left the wood. Beneath the surface will be meandering tunnels packed with powder. Sometimes there will be beetle larvae still present in the tunnels.

But why don't I find the beetles? The adults that make the exit holes are quite small ranging from 1/8" to 1" long, depending on their species. But they may not be numerous. They are short-lived and may be only present at night. So, don t be surprised if you don t see the beetles.

How do beetles get into a building? Some species get inside as eggs or larvae in construction lumber during the time a house is built or remodeled. New or used construction lumber should be examined carefully before it is brought inside. All of these beetle species must have bare wood to lay their eggs on, so wood that is painted, varnished, shellaced, sealed or waxed is safe as long as no bare wood is left exposed. Emergence of adult beetles from finished hardwood means that the infestation got started before the finish was applied. The larvae of some species can feed for three years inside the wood before they emerge.

Lyctid Powderpost Beetle

Lyctid Powderpost Beetle

Do infestations ever die out on their own? Yes. Because many species of beetles will not infest seasoned wood, they will not reinfest the wood they emerged from. Th three groups of beetles that can infest seasoned wood belong to one of three families (Lyctidae, Bostrichidae, Anobiidae). Details about these beetles are given below.

Lyctid Powderpost Beetles.

Identification: True powderpost beetles are small (from 1/8 to 1/4-inch) and are reddish-brown to black. Unlike Anobiid and Bostrichid powderpost beetles, the head of a Lyctid beetle is visible from above. These beetles have an 11-segmented antenna which ends in a two-segmented club. The tibia of each leg has two small spurs. Lyctid beetles are found in Nebraska.

Signs: The presence of small piles of very fine flour-like wood powder (frass) on or under the wood is the most obvious sign of infestation. Even a slight jarring of the wood makes the frass sift from the holes. There are no pellets or large bits of wood. The tiny exit holes are round and vary from 1/32 to 1/16 inch in diameter.

Lyctid infestations: Infestations of Lyctids are often introduced into structures in hardwood cabinets and furniture and molding that is made from infested lumber. Lyctids attack the sapwood of hardwoods with large pores: for example, oak, hickory, ash, walnut, pecan, poplar, wild cherry and many tropical hardwoods. Bamboo can also be infested. The size of the wood's pores is important because the female lays her eggs in the pores. Usually, only newer wood is infested because the larvae eat the starch in the wood. As the wood ages, its starch content decreases. Because softwoods have smaller pores and low starch content, they are not often infested. Eggs are never laid in varnished, painted, waxed, or finished wood.

Bostrichid Powderpost Beetles.
Wood-destroying Beetle Life Cycle

Bostrichid Powderpost Beetle

Identification: Most Bostrichid beetles are very small, being 1/8-inch in length and from reddish-brown to black in color, although some outdoor species that may infest firewood are larger. The typical Bostrichid body is long and cylindrical in shape. The wing covers have rows of deep pits and some species have spines or jagged margins on their rear end tips. The antennae are short; with the last three or four segments enlarged and saw-toothed. With the exception of one beetle that is not found in Nebraska, Bostrichid beetles have their head positioned below their prothorax where it is hidden from above.

Signs: Bostrichid beetles actually bore into wood to lay their eggs, so the first sign of an infestation is a circular entry hole from the egg tunnels made by the females. The exit holes made by adults are similar, but are usually filled with frass. The frass is meal-like and contains no pellets. It is tightly packed in the tunnels and does not sift out of the wood easily. The exit holes are round and vary from 3/32 to 9/32 inch in diameter. Bostrichid tunnels are round and range from 1/16 to 3/8 inch in diameter. If damage is extreme, the sapwood may be completely consumed.

Bostrichid infestations: Bostrichid beetle infestations are generally found in new hardwoods, although softwoods may be attacked. Bostrichids rarely cause significant damage in framing lumber and primarily affect individual pices of hardwood flooring or trim. Only rarely, will they attack and reinfest seasoned wood. Just because exit holes are found, does not mean that an infestation is active. The regular appearance of frass after it has been cleaned up is usually a sign of live activity.

Anobiid Powderpost Beetles.
Wood-destroying Beetle Life Cycle

Anobiid Beetle: Wood-destroying Beetle

Cigarette Beetle

Cigarette Beetle: Stored Food Products Pest

Drugstore Beetle

Drugstore Beetle: Stored Food Products Pest

Identification: Small brown beetles, ranging from 1/16 to 5/16 inch in length. The body shape is variable, ranging from long and thin to broadly oval. The head of this group of beetles is not visible from above. Two other Anobiids that infest stored products and could be confused with the wood-damaging species are the cigarette beetle and drugstore beetle. The prothorax of some species is bell-shaped. Antenna is variable and may be sawtoothed (serrate) or comb-shaped (pectinate). There are no spurs on the tibia of the leg as may be found in Lyctids and Bostrichids.

Signs: The frass of most Anobiid beetles contains numerous fecal pellets which are often stuck together in clumps. This is very different from the frass of Lyctid or Bostrichid beetles. The most obvious sign of an infestation is the accumulation of powdery frass and tiny pellets underneath infested wood or streaming from exit holes. The exit holes are round and vary from 1/16 to 1/8 inch in diameter. If there are a large number of holes and the powder is bright and light-colored like freshly sawed wood, the infestation is both old and active. If all the frass is yellowed and partially caked on the surface where it lies, the infestation has been controlled or has died out naturally. Anobiid tunnels are normally loosely packed with frass and pellets.

Anobiid infestations: These are important wood destroying beetles, but we are fortunate that they are not common in Nebraska. The furniture beetle, is the one that causes "wormwood" damage in the eastern U.S. and Britain. Anobiid beetles attack both hardwoods and softwoods, however the wood attacked is generally old and not newer wood. They will reinfest seasoned wood if environmental conditions are favorable. Attacks often start in poorly heated or ventilated crawl spaces and spread to other parts of the house. The control measures used for powderpost beetles depend on what type of wood item is infested, where the infestation is located, and the extent of the infestation.

Managing infestations:

Moisture: It is important to reduce excessive moisture in humid situations like crawlspaces, basements, and other locations; leaky roofs or plumbing should be repaired. Ventilate humid situations where possible.

Single items: If evidence is limited to a single board, piece of molding, or other item, removal and replacement is most effective and economical. Kiln drying kills larvae within infested lumber, but reinfestation is possible.

Furniture. Fumigation may be necessary to control a powderpost beetle infestation. There are no over-the-counter fumigants available to the public, so working with a pest control company that has the ability to fumigate pieces of furniture will be necessary. Not all structural pest control professionals are certified to do fumigation treatments, which can be very hazardous and require specialized training. Because fumigation is done with a poisonous gas, the piece of furniture or wooden item must be removed to a secure location to do this safely. Treating unfinished wood surfaces with a borate treatment or residual insecticide may control the infestation somewhat, but will not be as effective as fumigation.

Extensive infestations: If large areas of wood are infested an cannot be removed, the method for 100 percent control would be a structural fumigation. This involves working with a pest control company that has the capability of tenting the home (or parts of the home) and introducing a gas fumigant that will penetrate the infested wood. A second, less effective option would be to treat the wood using a borate or residual insecticide. Wood that is stained or painted cannot be surface treated unless the finish is sanded off and removed.

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