Your Guide to POWDERPOST BEETLES

Your Guide To POWDERPOST BEETLES

About the Author Understanding Dr. Michael F. Potter is a professor and entomologist at the Powderpost University of Kentucky, specializing in pests infesting buildings, people and property. Beetles Before joining UK in 1991, How to diagnose problems and develop a prudent plan for Potter worked in the pest management and customers. BY MICHAEL F. POTTER agrichemicals industry. He’s worked with wood- owderpost beetles are second only to termites in their infesting insects for many Pthreat to seasoned wood. Yet the pests still cause a lot of years, providing insights confusion. The chaos often starts with holes and powder ap- and advice to the public. pearing in flooring, cabinets or furniture. Other times, the damage is discovered during a routine wood-destroying insect inspection. Before you All photos, except as noted, arrive, the customer may have ©M.F. Potter. already received incorrect information about whether the PCT Media Group culprits are indeed powderpost beetles. Mistakes also are This educational aid is made determining if infesta- courtesy of PCT magazine, tions are active, and if so, how a monthly trade publica- tion distributed to pest they should be managed. This management professionals study guide will help you throughout North America. make better decisions when PCT magazine and its you encounter these pests. website, www.pctonline. com, is published by GIE Media, Valley View, Ohio. The Culprits. “Powderpost To order additional copies, beetle” is a term used to visit store.pctonline.com. describe several species of 1 3 small ( ⁄8- ⁄4 inch long) insects that reduce wood to a flour- like powder. The larvae make Figure 1. Powderpost beetles narrow, meandering tunnels tunnel through wood, producing in wood as they feed (Figure 1). fine powder and small exit holes.

Powderpost Beetles Fact Sheet Your Guide To POWDERPOST BEETLES

Bed bugs before and after engorgement.

Figure 2. Lyctid powderpost beetles. The powder is the consistency of flour.

Newly emerged adults mate and lay eggs the holes. Lyctids attack only wood products on or below the surface of raw, unfinished manufactured from hardwoods such as oak, wood. The eggs hatch into larvae that tunnel ash, walnut, hickory, poplar or cherry. Con- within the wood, emerging as adults, months sequently, problems typically arise in floors, to years later. Infestations are usually discov- cabinetry, molding, paneling and furniture. ered after noticing powder, accompanied by Tropical hardwoods (mahogany, obeche, small, round ‘shot holes’ in the wood surface. bamboo, etc.) are especially prone to infesta- These are exit holes where adult beetles have tion due to poor storage and drying practices chewed out of the wood after completing before importation. their development. Because the adults are Lyctid powderpost beetles do not infest active mainly at night, customers are more pine and other softwoods, so structural wood likely to see holes and powder than the members are generally immune from attack. beetles themselves. Occasionally a beetle may This is important to communicate to custom- be spotted emerging from an exit hole or on a ers, who often worry that infestations will windowsill, since some are attracted to light. spread into walls, studs, etc. Lyctids also The three most destructive groups of avoid construction plywood used for sub- powderpost beetles are the lyctids, anobiids, floors and sheathing (although plywood with and bostrichids. Each group contains several a hardwood veneer may sustain damage to species capable of damaging wood materi- the outer layer). als. Many similar-looking beetles that do After emergence and mating, lyctids locate not infest wood also appear in buildings. susceptible wood to lay their eggs. Ten to Correct identification is important to avoid 50 eggs per female are inserted into the tiny embarrassing, costly, and potentially litigious pores and vessels of unfinished hardwoods. mistakes (see sidebar, ‘Mistaken Identities’). Stained, varnished, or painted surfaces are immune from attack; beetles already within 1 1 Lyctid powderpost beetles are small ( ⁄16- ⁄4 infested wood, however, can emerge through inch), narrow and elongated, reddish-brown subsequently finished surfaces. Before de- to black beetles (Figure 2). Their emergence positing eggs, female lyctid beetles ‘test’ holes are round and about the size of a pin- the suitability of wood for the larvae, which head. The powdery dust feels like flour or fine require starches and sugars for development. talc and often accumulates in small piles near If the starch content of the wood is insuf-

Powderpost Beetles Fact Sheet Your Guide To POWDERPOST BEETLES

ficient (less than about 3%), the females will not use it for egg laying. Lower starch levels also make it harder for the larvae to complete their development. Lyctids are less particular about moisture than other types of powderpost beetles. Larvae can persist in wood with a moisture content as low as about 8%, which is common in temperature- controlled, indoor environments. However, at such low moisture levels, beetles develop more slowly, as occurs in older wood with declining starch content. In newly seasoned wood with abundant starch and other nutrients, egg to adult development takes less than a year. Con- versely, as wood ages, starch content de- clines and development slows to the point where some beetles may not emerge for two or more years, if at all. Consequently, lyctid infestations eventually cease and die off even without intervention — an important factor Figure 3. Bostrichid powderpost beetles often have when weighing options (see section, ‘Remedy- rasp-like bumps behind the head. Some species ing Infestations’). Small numbers of lyctid also have a pair of projecting spines at the end of the body. beetles already in the wood may continue to emerge for up to five years, in rare cases, even a bit longer. Customers should be unusual habit of boring directly into wood apprised of this possibility, and that the in order to lay eggs. These holes are devoid prolonged emergence is due to diminished of powder. Conversely, holes formed by suitability of the wood rather than re- beetles upon completing their development infestation by other beetles. are packed with powder. The powder/frass is more meal-like than lyctid powder and tends Bostrichid powderpost beetles vary in size to remain tightly packed in the holes and feed- depending on the species. Those most associ- ing galleries of the larvae. ated with wood products are reddish-brown Bostrichid powderpost beetles are more 1 1 to black ranging in length from ⁄8- ⁄4 inch. serious pests of hardwood than softwood, Compared to lyctids, bostrichids are less and there is little risk to structural framing narrow-bodied and flattened, and the head within homes. Similar to lyctids, bostrichids is oriented downward, appearing ‘hooded’ usually attack newly processed wood with (Figure 3). Many species also have tiny, high starch and moisture content. Tropical rasp-like bumps behind the head, sometimes hardwoods, including bamboo, are espe- accompanied by a pair of projecting spines cially prone to attack, which often occurs at the end of the body. Bostrichids create before importation. Like lyctids, bostrichids 1 1 circular ⁄8- ⁄4 inch holes in wood like other seldom re-infest wood after the first genera- powderpost beetles. Female beetles have the tion emerges. Nonetheless, extensive damage

Powderpost Beetles Fact Sheet Your Guide To POWDERPOST BEETLES

to infest moist wood; a 13-30% moisture content is required for development of the larvae. Besides needing wood moisture for larval development, high humidity is essential for egg hatch. At 65-95% relative humidity, more than 80% of eggs successfully hatch; below 60% humidity, hatch is reduced to zero. Consequently, infestations are most severe in damp crawl spaces, basements, garages, and unheated outbuildings. Buildings with central heating and cooling seldom have sufficient dampness to support beetle development in living areas or attics. Anobiids occur throughout much of the country. Structural infestations are more common in the southeastern and coastal states where humidity and temperature are high and crawl space construction is abundant. Unlike lyctids and bostrichids, anobiid powderpost beetles can digest the cellulose within wood, and are less dependent on starch and other nutrients that decline over Figure 4. Anobiid powderpost beetles can re-infest time. This enables them to attack and in- damp wood repeatedly. Massive damage to this fest wood regardless of age. In Europe, for beam occurred in a bourbon warehouse in Kentucky. example, some anobiid species continue to infest wood in buildings that are centuries old. can occur the first year due to a high initial Larval development occurs slowly, exceeding population and rapid development. 2-3 years if conditions are suboptimal. As a result, infestations are seldom obvious in Anobiid powderpost beetles are convex, red- buildings less than 10 years old. Although dish to dark brown beetles capable of attack- damage occurs slowly, the ability of emerging both hardwoods and softwoods (Figure 4). ing beetles to re-infest wood year after year They are sometimes confused with drugstore can lead to serious problems requiring treat- and cigarette beetles that also occur in homes ment and repair. but infest stored foods. The emergence holes Emergence of adults usually occurs dur- 1 1 are ⁄16- ⁄8 inch. Rubbed between the fingers, ing spring and summer. In nature, the beetles the powder feels gritty (although when the dwell in dead tree limbs or bark-free trunk source is oak or another hardwood this is scars. The adults are strong fliers and some are not the case). Unlike the groups discussed attracted to lights. Infestations within build- previously, anobiid powderpost beetles can ings may originate from infested lumber, fire- seriously damage beams, joists, and other wood, or from beetles entering from outdoors. structural components of buildings. Moisture is the most crucial factor affecting the destruc- Is the Infestation Active? Powderpost beetle tive potential of this beetle. Anobiids prefer infestations often die out of their own accord.

Powderpost Beetles Fact Sheet Your Guide To POWDERPOST BEETLES

Therefore, it is important to know whether Remedying Infestations. As noted previ- the infestation is active before taking action. ously, powderpost beetles, especially lyctids Active infestations usually have powder and bostrichids, typically enter buildings the color of freshly sawn wood streaming in lumber or manufactured items (flooring, from or accumulating near exit holes. Old, cabinetry, molding, paneling, furniture, abandoned holes will have no accompany- etc.). Infestation occurs after logs are sawn ing powder and will have taken on the aged into lumber and the wood sits in storage, or appearance of the surrounding wood (Figure during transit and distribution. Therefore, 5). If wood surfaces were previously stained, it is prudent for fabricators and installers old emergence holes will have traces of stain to inspect incoming materials for signs of or finish inside, whereas more recent holes beetles before turning them into finished will not. The same may be true of holes that products. Wood that is suspect should not are ‘angled,’ suggesting beetle emergence be used, especially if emergence holes or occurred before the wood pieces were cut. If powder is present. Some of the most serious accumulations of powder appear yellowed, infestations occur from using old lumber caked, or covered with dust or debris, the from a barn or woodpile to panel a room, damage probably is old. Careful observation lay a floor, or build an addition. may be necessary to distinguish new powder Customers should know there are options from powder dislodged out of old larval gal- for remedying infestations. Choosing the leries by vibrations. ‘best’ approach depends on such factors as Another way to confirm that an infestation extent of damage, potential for re-infesta- is active is to mark or seal any holes, sweep or tion, and cost — both financial and emotion- vacuum up all existing powder, and recheck al — to the parties involved. Wood-boring the wood for new holes and powder later on. beetle damage occurs slowly. A ‘wait and Since beetle emergence often occurs in spring see’ approach often makes sense, especially or summer, it is useful to wait until then to when it is unclear whether the infestation determine if new holes and fresh powder are is active. present. This makes particular sense when There are various reasons why some trying to determine whether an infestation is powderpost beetles, especially lyctids and active during colder months of the year. bostrichids, have a hard time re-infesting

Figure 5. Active versus inactive infestations. The former usually have fresh powder accompanying the emergence holes.

Powderpost Beetles Fact Sheet KNOW YOUR WOOD-BORING BEETLES: The #2 wood destroying insect Identify the problem 1. Examine exit holes. There will be frass the color of freshly cut wood in an Be prepared! Beetle infestations are sneaky— active infestation. most aren’t discovered until they’re already well 2. Confirm an active infestation by established! marking pinholes and rechecking While any insecticide will kill the wood-boring wood for new holes later. ® beetles it comes into contact with, Bora-Care 3. Listen for a chewing noise that older penetrates to kill insects that can’t be seen or detected. Once larvae may make during feeding. the wood is treated with Bora-Care, it’s no longer a food source and wood-boring beetles can’t infest it. Bora-Care provides Identify the beetle residual protection for the life of the wood. 1. Lyctidae – True powderpost 2. Ptinidae (Anobiidae) – Furniture & deathwatch 3. Cerambycidae – Old house borer 4. Bostrichidae: False powderpost

Identify your Bora-Care treatment plan 1. Whole house or spot treatments 2. New construction or remedial treatments 3. Foam, spray, inject

For more information about wood-boring beetles, see www.woodboringbeetles.com.

Remember, always read, understand and comply with the label. Bora-Care and Nisus Corporation are 100 Nisus Drive • Rockford, TN 37853 registered trademarks of Nisus Corporation. ©2019 Nisus Corporation #PCT-BCBTL-INS2-0619 800.264.0870 • www.nisuscorp.com KNOW YOUR WOOD-BORING BEETLES: The #2 wood destroying insect Identify the problem 1. Examine exit holes. There will be frass the color of freshly cut wood in an Be prepared! Beetle infestations are sneaky— active infestation. most aren’t discovered until they’re already well 2. Confirm an active infestation by established! marking pinholes and rechecking While any insecticide will kill the wood-boring wood for new holes later. ® beetles it comes into contact with, Bora-Care 3. Listen for a chewing noise that older penetrates to kill insects that can’t be seen or detected. Once larvae may make during feeding. the wood is treated with Bora-Care, it’s no longer a food source and wood-boring beetles can’t infest it. Bora-Care provides Identify the beetle residual protection for the life of the wood. 1. Lyctidae – True powderpost 2. Ptinidae (Anobiidae) – Furniture & deathwatch 3. Cerambycidae – Old house borer 4. Bostrichidae: False powderpost

Identify your Bora-Care treatment plan 1. Whole house or spot treatments 2. New construction or remedial treatments 3. Foam, spray, inject

For more information about wood-boring beetles, see www.woodboringbeetles.com.

Wood Replacement — Oftentimes, indications of beetle activity are limited to small sections or a few pieces of wood. The most efficient approach is often to remove and replace them (Figure 6). As an added precaution, it may be prudent to also replace wood pieces adjacent to any that are damaged since larval tunneling sometimes extends from one piece to the next. Beetle holes in any wood that was not replaced should be sealed and all visible wood powder removed so that old damage will not be mistaken for new. Arrangements can then be made with the client to inspect annually for a few more years to ensure activity has ceased. Although it cannot be forecast precisely when no more emergence will occur, future damage should be diminished. If additional holes do appear, an agreement can be made between the respective parties (seller, installer, etc.) to cover the cost of additional Figure 6. Replacing small sections of damaged wood wood replacement. can be an effective means of control. Moisture Reduction — Anobiid powderpost wood products within dwellings. As wood beetles in particular have high moisture ages, levels of starch, moisture, and other needs for survival. A wood moisture content nutrients decline to the point where the below about 15% and relative humidity pests can no longer complete their development. The declining number of adult beetles that do manage to emerge have a hard time finding mates. Propagation and spread are further diminished because most interior surfaces are finished — once stain, varnish, etc., is applied, wood surfaces are no longer suitable for laying eggs. Beetles emerging through such coatings were in the wood before the finish was applied. Although undersides of floors, cabinets, and furniture remain unfinished, declining starch and moisture makes re-infestation via these areas unlikely. The same is true of any beetles attempting to lay eggs in former emergence holes; sealing the holes further prevents this Figure 7. Moisture meters are useful tools for possibility. predicting potential re-infestation.

Powderpost Beetles Fact Sheet Your Guide To POWDERPOST BEETLES

below 60% during spring and summer Lethal Temperatures — Before wood is used is generally unsuitable for development. for construction or manufacturing, most of Therefore, it’s advisable to lower dampness the water is removed by air-drying or kiln in crawlspaces, basements, etc., by installing drying. Kiln-dried lumber is heated for a a vapor barrier, increasing ventilation/ period of hours to about 125-140°F. This is air circulation, and improving drainage. sufficient to kill all stages of powderpost Moisture meters are invaluable for measuring beetles and other insects that might be in the moisture content of wood and predicting the wood prior to heating. However, even the potential for sustained infestation (Figure wood that is properly kiln dried may become 7). Hand-held relative humidity meters also are infested during subsequent storage and useful tools for predicting viability of anobiid transit. The longer wood sits in a vulnerable eggs in crawlspaces. condition, the greater the chance beetles will find and lay eggs on the lumber. Residual Insecticides — Borate insecticides In recent years, some pest managers such as Bora-Care and Tim-bor are especially have begun heat-treating dwellings and useful against powderpost beetles. They furnishings for bed bugs. While it would are safe, non-staining, and often retain their be difficult to kill wood-boring beetles in protective properties for the serviceable built-in components like floors and cabinets, life of the wood. Depth of penetration into de-infestation of furniture and similar items wood depends on moisture content; the may be possible within a heat chamber. damper the wood, the deeper they generally Temperatures targeting powderpost beetles penetrate. At lower wood moisture levels would be similar to those used for bed (e.g., 10-15%, effective concentrations of bugs (120-135°F), although exposure times 1 1 borate penetrate only about ⁄8- ⁄4 inch — still might need to be lengthened up to 24 hours sufficient to kill newly hatched larvae before depending on wood thickness. they tunnel more deeply, thus breaking Powderpost beetles also can be killed by the cycle of reinfestation. Wood surfaces placing smaller items like woodcarvings must be unfinished since the spray will and picture frames in a deep freeze (0°F not penetrate water-repellent coatings. minimum) for at least one week. Freezers For this reason, borate insecticides are capable of reaching -20°F are able to kill all most suited for treating joists, beams, and life stages within 72 hours. other structural members. Borate sprays Before freezing, items should be placed are sometimes used to treat beetle-infested in plastic bags, or wrapped in polyethylene flooring, but the floor must be sanded to sheeting and sealed with tape. This prevents raw wood first. Apart from the expense frost and ice from forming on objects during and disruption, such measures are seldom chilling, and condensation after removal. After necessary since the emerging beetles freezing, objects should be allowed to return to (typically lyctids) are unlikely to re-infest. room temperature (for about 24 hours) before Furthermore, since the moisture content of being unwrapped or further handled. Some flooring in temperature-controlled buildings items become brittle at low temperatures, and is low (typically below 10%), borate this will help to reduce breakage. penetration would be minimal and likely would have little effect on larvae already Fumigation — Fumigation is generally an within the flooring. extreme measure for ridding dwellings of

Powderpost Beetles Fact Sheet Your Guide To POWDERPOST BEETLES

powderpost beetles. Current fumigants when materials became infected before containing sulfuryl fluoride are less installation. Generally, the longer wood sits effective on wood-boring beetles than in a vulnerable state during processing, dry- former compounds (e.g., methyl bromide). ing, distribution and storage, the greater the Consequently, de-infestation may not be chance beetles will find and lay eggs on the successful. Structural fumigation may be lumber. Consequently, wood suppliers often warranted when anobiid beetle infestations have more culpability for such problems have spread into walls, between floors, than installers do — especially when materi- and other areas where access for surface als were installed over a comparatively brief treatment or wood removal is impractical. period. Manufacturers and suppliers often The best way to avoid such problems is assume (incorrectly) that their wood prod- early detection and employment of other ucts could not possibly have contained live corrective measures. Portable items such as beetles when sold because the wood had furniture can be fumigated more efficiently formerly been kiln dried. Although proper and economically in trailers, vaults, etc. kiln drying is sufficient to kill all stages of insects, such wood can become infested Who’s Responsible? Common questions during subsequent distribution and storage. in powderpost beetle investigations are Consequently, blanket assertions by wood “how did the problem originate — and suppliers that their materials could not more pointedly ― who is responsible?” contain live beetles because it was kiln dried Such questions have particular relevance are invalid. to manufactured products like furniture, flooring and cabinetry. Lyctid and Final Thoughts. Powderpost beetle bostrichid powderpost beetles usually start infestations can be confusing and stressful. emerging from such items within a year It is important to diagnose the problem of installation or purchase. In almost all correctly to avoid unneeded effort and cases, the wood contained eggs or larvae at expense. Identifying the beetle involved and the time it was brought into the dwelling. whether the infestation is active are crucial This is significant because responsibility first steps. Other factors include the extent for treatment or replacement often resides of infestation, and type, age, and moisture with the manufacturer, supplier, or installer, content of the wood. Since beetle damage rather than the homeowner. progresses slowly, take time to educate While lyctids and bostrichids sometimes the parties involved and develop a plan of infest firewood, this seldom has anything action. Extremes such as removing an entire to do with infestations in dwellings. Also floor or fumigating the building are seldom unlikely is that the problem originated from necessary. beetles flying in from outdoors. With such Customers sometimes have concerns that infestations, materials with the most beetle powderpost beetles will harm the future holes and powder are the most likely source resale value of their home. Since infestations of introduction. For example, if most of rarely perpetuate indefinitely, this should the holes and powder are in cabinetry, it is not be a big concern. Many more homes doubtful the wood flooring was primarily have been treated for termites and have re- involved. tained their market value, and powderpost It is often hard to determine where and beetles are even less threatening.

Powderpost Beetles Fact Sheet Your Guide To POWDERPOST BEETLES

Mistaken Identities Many beetles that are not powderpost beetles occur within buildings. It is important to know the difference to avoid confusion and prevent unnecessary treatment and repair. Powderpost beetles are sometimes confused with similar-looking beetles infesting flour, cereal, grains, seeds, nuts, spices or pet food. Conse- quently, the source is often stored food items in kitchens, pantries, etc. (Figure 8). Another pest group often mistaken for powderpost beetles scavenge on surface molds associated with damp conditions. One of the most common is the foreign grain beetle (Figure 9). The beetles are 1 small (about ⁄16-inch long), brownish, Figure 8. These beetles, thought to be infesting a new floor, were living in a box and abundant, with large numbers often of dog biscuits. present throughout the dwelling. A distinguishing feature is the presence of a small projection/knob on each front corner of the shield-like segment behind the head. A microscope or other means of magnification is necessary to see this. Foreign grain beetles are one of a group of beetles that feed on molds and fungi growing on poorly seasoned lumber or wet plaster and wallboard. They often are a problem in newly built homes. When new homes are constructed, microscopic surface molds form on damp wood and sheetrock, which in turn attracts the beetles. In older homes, foreign grain beetles may be associated with plumbing leaks, condensation problems, or poor ventilation. None of the beetles in this category damage wood; once the moisture condition is resolved, the surface Figure 9. Foreign grain beetles are often mistaken molds disappear along with the for powderpost beetles (note the two small beetles. ‘knobs’ just behind the head).

Powderpost Beetles Fact Sheet