Wood-Boring Beetles in Homes

Wood-boring beetles in Homes Integrated Pest Management in the Home Three groups of wood-boring bee- IDENTIFICATION AND LIFE tles—powderpost, deathwatch, and CYCLES false powderpost (Table 1)—invade Powderpost Beetles and damage wood furniture as well as structural and decorative wood A subfamily of beetles in the family inside of buildings. The beetle larvae Bostrichidae (formerly referred to as the family Lyctidae) are known as pow- feed in and do most of the damage derpost beetles (Fig. 1), because larvae to wood, and when they reach the create a fine, dustlike powdered frass (a adult stage, they emerge through mixture of feces and wood fragments) round exit holes, which they create by that has the consistency of baking flour chewing through the wood surface. or talcum powder. This boring dust is Figure 1. Adult powderpost beetle, Lyc- Adults of some species also bore exit packed into the larval galleries (feeding tus planicollis. holes through plaster, plastic, and channels) in the wood but occasionally even soft metals that might cover the falls out of exit holes into small piles on underlying wood. floors or other surfaces. You might see other wood-boring bee- This fine, powdery frass distinguishes tles such as flatheaded or roundheaded powderpost beetles from other wood- borers and bark or ambrosia beetles boring beetles in homes (Fig. 2). It also in your home if you store infested differs from the larger, granular, and firewood inside. However, these typi- almost pepperlike pellets drywood ter- cally are forest insects that won’t attack mites leave behind; if you look closely wood structures or furniture. They at termite pellets, you will see they begin their life cycles on declining have ridges on their sides. Figure 2. Powderpost beetles produce much finer boring dust (left) than other trees that are old or that have sustained wood borers such as deathwatch beetles fire or insect damage. Sometimes these Powderpost beetles attack hardwoods, in the family Anobiidae (right). forest insects are present in trees when apparently because these woods have they are milled into wood products, pores into which they can lay eggs; and they might cause alarm when they softwoods don’t have such pores. The with high starch content; the starch emerge from infested wood used in large pores in bamboo also make it a content in softwoods is nutritionally low for these beetles. They will attack newly constructed buildings. However, favored host material for powderpost beetles. In addition to large pore size, wood that is very dry and that has a they aren’t able to reinfest the wood in powderpost beetles also prefer wood moisture content as low as 8%. these structures. Table 1. Certain species of wood wasps also Frequently Encountered California Species of Powderpost, Deathwatch, and False might emerge from infested wood used Powderpost Beetles.1 in new structures. See Pest Notes: Wood Group name Common name Latin name Wasps and Horntails for more informa- tion. Invasive wood-boring insects powderpost old world lyctus beetle Lyctus brunneus (Stephens) (Lyctinae)2 southern lyctus beetle Lyctus planicollis LeConte often arrive as hitchhikers from other western lyctus beetle Lyctus cavicollis LeConte continents on solid wood packing deathwatch Pacific deathwatch beetle Hemicoelus gibbicollis (LeConte) material such as pallets or in a ship’s (Anobiidae) dunnage, and some of the key beetle false powderpost black Polycaon Polycaon stoutii (LeConte) pests of wood in structures have likely (Bostrichidae) leadcable borer Scobicia declivis (LeConte) established worldwide distributions 1 Based on a survey conducted in March 2010 of some of the principal insect collections in California—Bohart this way. Museum, California State Collection of Arthropods, and Essig Museum. 2 Recently a taxonomic change has been recommended to incorporate the former family Lyctidae as a subfamily Lyctinae within Bostrichidae. However, the biology and field visual signs of damage for the subfamily Lyctinae remain unchanged. EST OTES Publication 7418 PUniversity of California N Statewide Integrated Pest Management Program Agriculture and Natural Resources June 2010 June 2010 Wood-boring Beetles in Homes Adult powderpost beetles most often dation timbers, and some types of fur- select and lay eggs in wood such as oak, niture. You’ll typically find this beetle ash, hickory, mahogany, and walnut, in old wood or wood that is partially and infestations are most likely to oc- decayed. Deathwatch beetles prefer cur in wood paneling, molding, floor- wood that is more moist—greater than ing, window and door frames, plywood, 14% moisture content—than what pow- bamboo articles, and furniture. Infesta- derpost beetles prefer, so they might be tions can occur if beetles or larvae are less of a problem in houses with central brought into a building in furniture, heating and air conditioning; you are firewood, or wooden decorative articles. more likely to encounter them in damp sub areas, basements, or outbuildings. Figure 3. Powderpost beetles leave tiny, Sometimes the only sign of infesta- Unlike powderpost beetles, deathwatch round exit holes in wood after they tion is the tiny, round exit holes made beetles in California are more likely to emerge as adults. by the emerging adult beetles (Fig. 3). invade structures from wild popula- Once they emerge, the winged adults tion sources located outdoors. spread to other wood surfaces where they deposit eggs onto unfinished Deathwatch beetle larvae fill their gal- surfaces or in cracks or other open- leries with very small pellets of frass ings. They also tend to fly toward light, (smaller than the pellets drywood ter- so you’ll typically find dead adults on mites produce), which gives their frass windowsills after they have tried to a slightly grittier consistency than that disperse. of powderpost beetles but not as coarse as that of false powerpost beetles. How- They have a life cycle ranging from 3 ever, like powderpost beetles, the lar- Figure 4. Adult deathwatch beetle. months to more than 1 year, depend- vae (Fig. 5) do most of the damage, and ing on temperature, humidity, and the their frass is packed in the galleries and nutritional quality of the wood. Adult is visible only when larvae or adults powderpost beetles usually are shades push it out through emergence holes. of brown to red. Species frequently Holes that deathwatch beetles leave encountered in California structures can be of various sizes, whereas those include the old world lyctus beetle, Lyc- from powderpost or false powderpost tus brunneus; the southern lyctus beetle, beetles tend to all be the same size. Lyctus planicollis; and the western lyctus beetle, Lyctus cavicollis. Adults are reddish to dark brown and lay eggs in crevices, small openings, or Deathwatch Beetles pores of unfinished wood. It can take 2 Figure 5. Deathwatch beetle larva. Wood-boring beetles in the family years to complete each generation. The Anobiidae are known as deathwatch species frequently encountered in Cali- beetles (Fig. 4). They are closely related fornia is the Pacific deathwatch beetle, to the drugstore and cigarette beetles, Hemicoelus gibbicollis. which are stored-products pests. Adults communicate with each other False Powderpost Beetles and probably locate mates by tapping Wood-boring beetles in the family their heads against wood, usually at Bostrichidae are sometimes known as night. Deathwatch beetles might have false powderpost beetles. False pow- acquired their name during medieval derpost beetles colonize a variety of times in Europe when people heard the hardwoods and sometimes softwoods. Figure 6. Frass-packed galleries made tapping while sitting up with a sick or Tropical species of Bostrichidae fre- by leadcable borer, a false powderpost dying person during the night. Legend quently are imported into the United beetle, in redwood. This frass is much has it they attributed the sound to the States on bamboo articles or on woods coarser than that produced by powder- tapping of the staff of the scythe of the such as Philippine mahogany or lauan. post or deathwatch beetles. grim reaper coming to take away the soon-to-be deceased. Unlike female powderpost and death- terials then deposit their eggs in pores watch beetles, which lay their eggs or cracks within the tunnel. Larvae of Deathwatch beetles primarily infest while on the wood surface, false pow- false powderpost beetles pack their gal- softwoods, especially Douglas-fir, derpost beetle females bore a tunnel, leries very tightly with frass that has which is used in girders, beams, foun- or egg gallery, into wood or other ma- the consistency of coarse powder simi- ◆ 2 of 4 ◆ June 2010 Wood-boring Beetles in Homes lar to powdered borax soap (Fig. 6). The MANAGEMENT texture of this frass is the most gritty The first step in managing wood- of the three groups and distinguishes boring beetles is identifying the group false powderpost beetles from true involved in the problem. Two quick powderpost beetles and deathwatch diagnostic tests, the ballpoint pen test beetles. and the frass test (Table 2), can help distinguish among the three groups In buildings, false powderpost beetles of wood-boring beetles. Detection can infest floors, furniture, hardwood be difficult, because much of their life paneling, and other wood materials. cycle takes place beneath the wood Adults of some species bore through Figure 7. Head and thorax of a lead- surface and in hidden wood junctions cable borer showing the humpback soft metal such as lead and silver as where a homeowner or inspector might appearance typical of false powderpost well as plaster and other nonwood not easily detect them. beetles and deathwatch beetles. materials, searching for sites to deposit eggs or protection from weather ex- Wood-boring beetles are difficult to tremes. This gives rise to the common control once an infestation has begun. types of pests is an important phytos- name “leadcable borer” for one species, Therefore, prevention is the best man- anitary regulation adopted by current Scobicia declivis, because of its habit of agement method.

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