Beetles (Order Coleoptera)

Pest Management In and Around Structures September 26, 2013 Print Friendly and PDF
Management of Pest Insects

in and Around the Home


Beetles (Order Coleoptera)

All beetles can be recognized by two pairs of wings. The front pair (called elytra) are hard and thickened or shell-like; elytra cover and protect the membranous flight wings underneath.

Ambrosia beetle
Ambrosia beetles (Curculionidae: Scolytinae: many species): Small (1/8 to 3/16 inch), robust beetles. Head concealed and protected by rounded pronotum (upper thorax); antennae with large, flat club. Habits: Adults burrow into wet, newly-cut wood to create galleries where they deposit eggs. The adult inoculates the secluded galleries with a fungus, referred to as ambrosia, that the larvae eat. Ambrosia fungus needs wet conditions to
grow (i.e., newly cut wood or recently debarked logs). The galleries are stained blue by the fungus. Ambrosia beetles do not eat wood. Interventions: Beetle problems disappear when the wood dries out. Insecticide treatments are rarely needed and not useful because these beetles (adults and larvae) do not eat the wood. Might Be Confused With: various powderpost beetles.

Broad-diet anobiid powderpost beetle
Powderpost beetles (Anobiidae and Bostrichidae: various species): Powderpost is a term used to describe several species of wood-eating beetles that feed (as larvae) on lumber (e.g., crawlspaces) and furniture grade (e.g., flooring) wood and that reduce the wood to a fine, flour-like powder (called frass). Frass is insect excrement. The most common families of powderpost beetles are the Anobiidae and Bostrichidae (including Lyctinae). Anobiid and non-lyctine bostrichid powderpost beetles attack both hardwoods and softwoods, whereas lyctines attack only hardwoods. All three can re-infest the wood from which they have just emerged, but lyctines and anobiids more so than bostrichids. Wood attacked by lyctine and anobiid powderpost beetles can be greatly damaged. Characteristic signs of powderpost beetle activity is the presence of small, round holes (1/16 to 5/16 inch diameter) in the wood. The holes are the result of the adult beetle, having just emerged from its pupal case, chewing its way out of the wood to free itself to the outside. When adult powderpost beetles emerge from the wood, they emerge perpendicular to the wood’s surface, creating an almost perfectly round exit hole. Active infestations are characterized by frass streaming from or accumulating around the exit hole on the wood’s surface. Adult
powderpost beetles are rarely seen. Exit holes with no frass present is evidence of a prior infestation, but not necessarily one that is still active.

Visual evidence (frass streaming from exit holes) of an active anobiid powderpost beetle infestationin a crawlspace joist.
Anobiid powderpost beetles (Anobiidae: Euvrilletta peltata): The broad-diet anobiid powderpost beetle, E. peltata, is about 1/4 inch, and reddish brown to dark brown. Body cylindrical, elongated, covered by fine, gold-colored hair and with long, serrated antennae. Elytra lined with rows of tiny pits. Head covered by the hood-like pronotum (upper thorax) when viewed from above. Adults, however, are rarely seen. Active infestations in crawslpaces usually diagnosed by the presence of joists with frass streaming from beetle exit holes. Live adults most commonly found on crawlspace joists in June in Georgia during their annual three to six week period of emergence. Other representatives of this group include the furniture beetle (Anobium punctatum), the deathwatch beetle (Xestobium rufovillosum), and the eastern deathwatch beetle (Hemicoelus carinatus). Habits: Most common wood-eating beetle in crawlspace wood is the broad-diet anobiid  Powderpost beetle. When adult beetles emerge from infested crawlspace joists (May and June in Georgia) they leave a 1/8 inch diameter, round hole in wood with frass streaming from holes in joists. Following emergence, beetles mate, females lay eggs (typically on the same board they emerged from), and then die within weeks. Eggs hatch and the larvae bore into the wood where they consume it until their emergence 1-3 years later, at which time the cycle repeats. Most commonly infests wood with a high moisture content— typically crawlspaces with no vapor barrier and/or poor ventilation. Also found in buildings that are only intermittently heated or occupied (hunting cabins, second homes, etc.), as moisture is allowed to build in the wood of these structures. Readily re-infests susceptible wood. Interventions: In  crawlspaces infested by this beetle, apply products containing the active ingredient disodium octaborate tetrahydrate (DOT) to all exposed surfaces of unfinished wood in infested areas (where fresh frass is found). Improve overall crawlspace ventilation. Install a vapor barrier if one is not present. Might Be Confused With: wood borers, ambrosia beetles, drugstore beetles.

True powderpost beetle
True powderpost beetles (Bostrichidae: Lyctinae: principally Lyctus spp.): Adult beetles 1/8 to 3/16 inch, cigar shaped, brown to black, with 11-segmented antennae where the last two segments are enlarged and form a club. Habits: True powderpost beetles infest hardwoods only; they will also infest bamboo. Most commonly reported from hardwood floors less than 5 years old, but can be found emerging from any item made of hardwood. Wood is infested prior to its final use. For example, hardwood floors are infested prior to their installation in the home, and the adults emerge soon thereafter, typically within a year or two of introduction into the home. The best evidence of an active infestation is round holes in wood (1/16 inch diameter) surrounded by frass (or streaming from the hole) the consistency of baby powder and a beetle identified by an entomologist. Can re-infest susceptible hardwoods, and do considerable damage, if conditions are favorable (successful mating and the availability of an unfinished hardwood surface). They do not infest structural wood (softwoods), such as pine or fir, so will not spread from infested items to become a structural pest. Interventions: Replacement of infested wood (for example, individual planks in a hardwood floor) is the best option. Might Be Confused With: sawtoothed grain beetle, flour beetle, other small beetles.

False powderpost beetles (Bostrichidae excluding Lyctinae: many species): The most commonly encountered false powderpost beetles are 1/8 to 3/8 inch, elongate and cylindrical, stout, and black to reddish brown. The head is not visible from above, but is hidden from view by a large, hood-like pronotum (upper thorax) with stout, cuticular spines along the rounded front edge. False powderpost beetles have short, serrate antennae with the terminal three to four segments enlarged (club-like). Elytra often end in distinct spines. Exit holes range in size, depending on beetle species. Exit hole size overlaps with exit hole size made by both true powderpost beetles and anobiid powderpost beetles, but larger false powderpost beetles leave large, round exit holes larger than any hole left by a true powderpost beetle or an anobiid powderpost beetle. Habits: False powderpost beetles are less economically important than either true powderpost beetles or anobiid powderpost beetles. They can infest rough cut lumber where strips of bark have been left intact. Unlike true powderpost beetles and anobiid powderpost beetles, adult female false powderpost beetles burrow into the wood where they deposit their eggs; true powderpost beetles and anobiid powderpost beetles lay eggs on the outer surface of the wood. False powderpost beetles attack both hardwoods (preferred) and softwoods that have a high moisture content (i.e., newly cut wood). May also infest pithy plants used in dried floral arrangements such as grapevine wreaths. Also attack wicker. Can re-infest, but not wood that has seasoned and dried considerably (to less than 10% moisture) since the initial infestation. Re-infestation is uncommon because aged wood is considerably drier than newly-cut wood. Interventions: Ensure that bark strips are removed from freshly-cut wood. Apply products containing the active ingredient disodium octaborate tetrahydrate (DOT) to prevent re-infestation, fumigate, freeze or remove the infested material. Might Be Confused With: anobiid and true powderpost beetles, ambrosia beetles.

Drugstore beetles and antennae (inset)
Drugstore beetles (Anobiidae: Stegobium paniceum): Small, 1/8 to 3/16 inch, light brown beetle with antennae ending in three broadened segments. Head concealed by helmet-like pronotum (upper thorax) and elytra with longitudinal rows of pits. Habits: This somewhat common stored product pest consumes items in the home of animal and plant origin (dried foods in the pantry, dog treats, etc.). Interventions: Find infested item(s) and discard. Clean up spilled food. Store potentially susceptible items in tightly sealed containers. Never treat human food sources with an insecticide. For more detailed information see University of Georgia Extension bulletin #1378, Stored Product Pests in the Home, at caes.uga.edu/publications. Might Be Confused With: other beetle pests of stored products, anobiid powderpost beetles.

Carpet beetles (Dermestidae: Anthrenus spp.): Adults 1/16 to 1/8 inch, ovalshaped, and calico colored. Larvae 1/8 inch, hairy, oval-shaped, slow-moving, and cryptic. Habits: Most homes are populated by a small number of carpet beetles, but because they are somewhat cryptic (slow moving, small, and inconspicuous) they are rarely seen. Larvae, but not adults, feed on products in the home that are of animal origin (feathers, wool, fur, hair, silk, skins, dry animal food, etc.) but will also feed on dead insects (found on window sills, in wall voids, and in light fixtures). Carpet beetles do not consume modern shirts and carpets, as they are made from cotton or synthetic fibers. Adults feed on pollen outdoors. Interventions: Find infested article(s) and remove. Vacuum insects and discard bag, and especially watch for re-infestation. Wash, steam-clean or dry-clean all items of animal origin,  especially wool. Have infested textiles professionally cleaned. If desired, apply a spot treatment with an appropriately labeled residual spray to the floor around the infested item(s). Might Be Confused With: warehouse beetle (Dermestidae: Trogoderma variabile), bed bugs.

Ground beetles (Carabidae: many species, especially Harpalus spp.): Numerous species, 1/4 to 1 inch. Common species are black—some shiny, some dull or flat black. One species, called the caterpillar hunter, is an iridescent green, 1 inch ground beetle. Hardened elytra, often with visible, longitudinal furrows or pits. Many species with strongly-serrated mandibles, indicative of a predatory insect. Habits: Fast-crawling, highly beneficial predators of other insects. Some species are attracted by insects that have been attracted to exterior lights. Harbor in log piles, leaf litter, and under flat items, such as boards, lying on the ground. Ground beetles are strongly attracted to lights. Interventions: Follow suggestions under section titled Proactive Pest Management. It is especially important to eliminate harborage, install doorsweeps, and alter lighting. Ground beetles are highly beneficial, predatory insects. Attempts should be made to conserve them. However, if desired apply a spot treatment with an  appropriately labeled residual spray directly to beetles (spray only outdoors). Might Be Confused With:cockroaches, other similarly-sized beetles.

Multicolored Asian Lady beetles (Coccinellidae: Harmonia axyridis): Also referred to as ladybugs or ladybird beetles. Oval-shaped, 1/4 inch, black and white thorax with or without black spots on red or orange elytra. Common insect in gardens. Habits: Highly beneficial, predatory beetle as adults and larvae, mostly of aphids and scale insects. Become nuisance in the Fall when they begin searching for overwintering sites inside homes and other structures. Interventions: Follow suggestions under section titled Proactive Pest Management. It is especially important to make sure all windows are screened, that doors remain closed, and doorsweeps are installed on all exterior doors. Before lady beetles begin to seek refuge indoors (Fall), take action to (1) seal all cracks 1/8 wide or wider, and (2) spot spray around all potential entry points with an appropriately labeled residual spray. Reapply insecticide treatments, per label specifications, through the end of November/early December. Interventions should be implemented early enough (mid-September) so that preventative measures are in place before the onset of lady beetle migration indoors. If lady beetles get inside the best solution is to vacuum them. Insecticide treatments indoors are not recommended. If lady beetles die inside walls or in attics their carcasses accumulate and may attract other insects that eat them, especially carpet beetles. It is often best to seek help and advice from a pest management professional experienced in lady beetle control. For more information see publication Multicolored Asian Lady Beetle, at ipm.osu.edu/lady/lady.htm.Might Be Confused With: kudzu bugs, brown-marmorated stink bugs boxelder bugs.

Lesser Mealworm beetles (Tenebrionidae: Alphitobius diaperinus): Also referred to as litter beetles or darkling beetles. Adults small (1/4 inch), broadly-oval, moderately convex, black or brownish black shiny beetles with longitudinal grooves on the elytra. Antennae with increasingly larger segments; each antennal segment round. Habits: Often associated with chicken litter. Adults are attracted to lights and are strong fliers; able to fly long distances from site of origin. Found on products already damaged by molds. Interventions: For homes with constant pressure (such as homes near chicken  production areas or near agricultural fields where chicken litter is spread), exclusion is generally best. Take action to seal all cracks 1/8 wide or wider. It is especially important to make sure that all windows are screened, that doors remain closed, and that doorsweeps are installed on all exterior doors. Follow suggestions under section titled Proactive Pest Management. Using yellow light to decrease attraction may also help. If desired apply a spot spray, around all potential entry points, with an appropriately
labeled residual spray. Might Be Confused With: ground beetles. Sawtoothed Grain beetles (Silvanidae: Oryzaephilus surinamensis): Very small (1/16 inch), slender, dark brown beetle with characteristic teeth along each side of the prothorax. Habits: One of the most common pests of stored products in the U.S. Infests common foods in pantries and food closets. Mostly crawls, rarely flies, and can be long-lived. Interventions: Find infested food (cereal, bird food, crackers, oatmeal, etc.) and discard. Clean up spilled food. Store potentially susceptible items in tightly sealed containers. Never treat human food sources with an insecticide. For more detailed information see University of Georgia Extension bulletin #1378, Stored Product Pests in the Home, at caes.uga.edu/publications. Might Be Confused With: true powderpost beetles, flour beetles.

Sugarcane beetles (Scarabaeidae: Euetheola humilis): Oblong- to oval-shaped, 1/2 to 5/8 inch, flat or shiny black to brownish black robust beetle with longitudinal rows of slight indentations on hairless elytra. Large, strong, spiny forelegs for digging. Habits: One or two population peaks (Spring and late Summer [August]) per year. Beetles may be very numerous when present. Short-lived adults strongly attracted to lights at night. At sunrise adults attempt to burrow away from sun no matter where they are, sometimes resulting in damage to roof shingles, pliable rubber caulking and sealants along expansion joints, expansion papers, etc. Interventions: Turn off lights during peak flight times, change to yellow lights, or use flood lights, positioned away from but pointing towards the building, to attract beetles away from the building. If desired, apply a spot treatment with an appropriately labeled residual spray to areas beetles aggregate, such as in corners and along seams where horizontal and vertical surfaces meet. Might Be Confused With: numerous other black scarab beetles, ground beetles.

White-fringed beetles (Curculionidae: Naupactus leucoloma): Longitudinally striped light to dark brown beetle, 1/4 to 3/8 inch, with a somewhat distinct beak (rostrum) and elbowed antennae. Habits: Larvae feed on roots of grass, and some agricultural crops, followed by punctuated adult emergence in Summer, sometimes in large numbers. Can be especially numerous near agriculture fields. White-fringed beetle activity is seasonal and predictable in occurrence. Interventions: Problems often cease on their own, so that insecticides are not needed. Follow suggestions under section titled Proactive Pest Management. It is especially important to install
doorsweeps. If desired, apply a spot treatment with an appropriately labeled residual spray directly onto beetles (spray only outdoors). Might Be Confused With: other weevil species, ground beetles.

Wood-boring beetles (Cerambycidae and Buprestidae: many species): Wood-borer is a general term that refers to the larval form of beetle species in either the family Cerambycidae or Buprestidae. They infest both hardwoods and softwoods. Adult cerambycids (called long-horned beetles) are elongate, cylindrical and 3/8 to 1 inch, often with antennae as long or longer than the body. Larvae are referred to as roundedheaded borers. Adult buprestids (called metallic wood-boring beetles) are 3/16 to 3/4 inch, bullet shaped, often metallic blue and/or emerald green. Larvae are referred to as flat-headed borers. Because adult beetles are rarely seen or found, diagnosis of
infestation in wood is usually dependent upon the morphology and size of the exit hole made by the adult beetle after it emerges from the wood. Long-horned beetle exit holes are nearly round to slightly oval, with a 1/8 to 3/8 inch long diameter (longdiameter never more than twice the short-diameter), while metallic wood-boring beetle exit holes are elongated, flattened ovals with a 3/16 to 1/4 inch long-diameter (long-diameter approximately 3- to 4-times the short-diameter). Habits: Wood-borers infest wood soon after the tree is felled, but before bark is removed. They cannot infest seasoned, processed lumber (in lumberyards or dimensional lumber in-service) or
trees that have been debarked. Infestations are more common in wood cut from one’s own property, but not kiln-dried or debarked quickly enough. They can also infest rough cut lumber where strips of bark have been left intact. Following mating, females lay eggs on the bark. Eggs hatch, and larvae burrow into and begin feeding just under the bark. They then move to the sapwood where they will remain for several years, until emergence, while consuming the wood. For various reasons, larvae may survive the milling process and are then built into structures using infested wood (structural lumber or logs for log homes). Adult wood-borers most often emerge from wood
1-3 years after construction. Generally, development time is quicker in wood with elevated moisture (logs), and can be delayed by several years in dry or drying wood (dimensional lumber). Exit holes are the result of the adult beetle chewing its way out of the wood to free itself to the outside. When beetles emerge, they are looking for a mate and then must find a tree with bark on it. Like the powderpost beetles, when adult wood-borers emerge from the wood they emerge perpendicular to the wood’s surface. Active infestations are characterized by frass (beetle excrement) streaming from the hole. Exit holes with no frass present are evidence of a prior infestation,
but not necessarily one that is still active. Interventions: None needed as these beetles will not re-infest, unless the wood contains moisture and has bark present and females are successfully mated. Beetle emergence holes are an aesthetic problem. The feeding damage done by larvae is not known to compromise the structural integrity of the wood. Generally, seek help from a professional pest control company to determine (a) beetle identification, (b) whether the  infestation is active or not, and (c) options for control, if needed. Obtain help with positive beetle identification from an entomologist. Control recommendations are entirely dependent upon beetle identification and infestation status. Might Be Confused With: old house borer.

Old House borer (Cerambycidae: Hylotrupes bajulus): Diagnosis of an Old House borer (OHB) infestation is typically based on: (a) exit hole morphology (exit holes elongated, flattened ovals 1/4 to 3/8 inch long-diameter never more than twice the short-diameter); (b) frass (a fine powdery texture where individual pellets are barrelshaped); and (c) ridged galleries made by larval feeding. When larvae can be obtained, they can be identified by the
presence of three ocelli (eyes), in a row, on the head. Larvae can sometimes be heard chewing in the wood. Adults are rarely seen, but are elongated (5/8 to 1 inch), somewhat flattened, brownish black beetles with moderately long antennae (at least 1/3 the length of the body). Margins of pronotum  (upper thorax) covered with numerous gray to white, short hairs. The center of the pronotum is naked, and contains two knobs that appear eye-like. Habits: The OHB feeds only on softwoods (mostly pine) and it prefers wood less than 10 years old with a moisture content greater than 10%. It is a species of wood-boring beetle in the family Cerambycidae (see section above on wood borers). It is not native to the U.S. It is singled out here because unlike the other wood-borers in North America it can infest seasoned, dimensional lumber (at the lumber yard) before it is used in construction; like other cerambycids, it can also attack recently  felled, barked or debarked, trees. Most OHB infestations are built into structures by using previously-infested softwoods (i.e., construction materials, pine floors, log homes) during construction. What makes the OHB different is that if conditions are favorable (successful mating upon emergence from infested wood and then location of a softwood with an adequate moisture content), it can then infest and continue to re-infest structural softwoods in the home. In contrast, the wood borers (mentioned above) cannot. Because they are built into homes, detection of OHB infestations is most typical in structures that are less than 10 years old. Development time (egg to adult emergence from wood) is strongly dependent upon wood moisture. Under the most favorable conditions (wood moisture content 15 to 25% [for example, logs in a new log home]), beetles can develop in 2-5 years, but development may take up to 10 to 15 years in exceptionally dry wood (wood moisture content less than 10% [for example, dry (and drying), seasoned dimensional lumber]). The senior author of this bulletin once acquired a piece of OHB-infested pine flooring (age unknown) and an OHB adult emerged from it 5 years later. Even though OHBs can infest susceptible wood in the home, survival of first instar larvae is low in wood with exceedingly low moisture content (less than 10%). Because of changes in wood-handling procedures over the past few decades, incidence of OHB infestations in homes has declined
dramatically. Although the vast majority of OHB infestations found in the home do not result in spread into other structural softwoods, the initial infestation (built into the structure) can do considerable damage to structural softwoods prior to adult emergence. When an OHB emerges, it must find a mate, successfully mate, and then the female must find a piece of susceptible softwood—i.e., wood with a moisture content greater than about 10%. Interventions: Application of products containing the active ingredient disodium octaborate tetrahydrate (DOT) to the surface of lumber can act as a deterrent to infestation and re-infestation. Localized treatment of active infestations or wood replacement, if possible, are other options. Fumigation should be considered for widespread infestations. Consult with a pest management professional in severe infestations. Might Be Confused With: many other species of wood borers in the family Cerambycidae and Buprestidae.

 

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.