A Pantry Pest “Morphs” Into Bark Beetles

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I recently received an e-mail message from a homeowner asking for help with small beetles found throughout their home collecting on window sills.  The concerned homeowner had used online resources to “identify” the beetles as a pantry pest.


However, an attached image revealed the born identity of the culprits to be Bark Beetles (family Curculionidae, subfamily Scolytinae).  These tiny beetles range in color from brown to black.  They measure around 1/8” long; some are slightly larger, some smaller.  Most are cylindrical-shaped, but some are a bit more robust.


Bard Beetles


In general, as the pictures below demonstrate, it’s understandable for bark beetles to be mistaken for pantry pests.  Cigarette Beetles (family Ptinidae, Lasioderma serricorne) and Drugstore Beetles (a.k.a. biscuit beetle) (family Ptinidae, Stegobium paniceum) bear a strong resemblance.


Cigarette Beetle


Cigarette Beetle


Despite their many common names, cigarette and drugstore beetles may infest a wide range of dried plant products.  Some of the cigarette beetles pictured in this Alert were found in a cayenne pepper product, no doubt singing a beetle version of “A Hot Time in the Old Town.”  The bag pictured below shows beetle-processed poultry chick starter food.


Cigarette Beetle


Cigarette Beetle


It's understandable for a homeowner to be concerned about pantry pests.  It can be difficult and time-consuming to eliminate an infestation.  Management involves tracking down and destroying the point source and then examining a wide range of products throughout a home, including inside an attached garage, to determine how far the infestation has spread.  Along the way, it's a good idea to place vulnerable products in sealed plastic containers.


Bark beetles inside a home would be short-lived nuisance pests.  There's nothing for them to eat.  Bark beetles focus their attention on stressed, dying, or dead trees.  As their name implies, they bore through the bark to tunnel and feed on the phloem as illustrated in the graphic below.  They don’t attack processed wood.


Bark Beetles


Bark Beetles


Bark Beetles


So, why would large numbers of bark beetles be found in a home?  This was a "first" for me.  However, a phone conversation with the homeowner revealed a key piece to the puzzle.  The homeowner had a large stack of firewood in their basement to feed a wood-burning stove.  Storing a large quantity of firewood in their basement was a common practice in past years, but they hadn’t burned through their indoor wood supply this year owing to relatively mild winter weather.



Firewood Nuisance Pests

Temperature plays an important role in insect development as well as in triggering certain behaviors such as adult emergence.  This means that accidental home invaders may emerge at unexpected times from firewood stored indoors.


A common home interloper that may emerge from firewood is the Painted Hickory Borer (Megacyllene caryae).  This borer is a type of longhorn beetle (family Cerambycidae), so named because of its long antennae.  


Painted Hickory Borer


Painted Hickory Borer


Painted hickory borers will only infest dead trees that died within one year or raw wood (e.g., firewood) that has been cut for less than one year.  They target a wide range of hardwoods including their namesake host as well as ash, black locust, hackberry, honeylocust, oak, Osage orange, walnut, butternut, and occasionally maple.


Painted hickory borers are sometimes mistaken for another native longhorn beetle that belongs to the same genus, the Locust Borer (M. robiniae).  Both beetles are about the same size and share similar markings.  However, locust borer adults emerge in late summer to early fall at about the same time that common goldenrod (Solidago canadensis) is in full bloom.  In fact, locust borer adults are commonly spotted on goldenrod partaking of the pollen and nectar.


Painted Hickory Borer


Not every longhorn beetle sports long antennae.  Prior to the collapse of ash in Ohio from Emerald Ash Borer (EAB) (Agrilus planipennis, family Buprestidae), the Banded Ash Borer (Neoclytus caprea, Cerambycidae) was another beetle that commonly emerged from firewood in the spring.  It has relatively short antennae for a longhorn beetle.  Although ash is its preferred host, the banded ash borer may also be found in oak and hickory firewood.


Banded Ash Borer


These big beetles as well as the much smaller bark beetles present no risk to wood furniture, flooring, paneling, or other processed wood in homes, or wood used in home construction.  They are just nuisance pests if they find their way into homes.  However, their sudden appearance can be a surprise and cause concern; particularly inside log homes.


Other insects may also stagger from firewood to the dread and consternation of homeowners.  These include Carpenter Ants (Camponotus spp.), Eastern Subterranean Termites (family Blattodea, Reticulitermes flavipes), and Pennsylvania Wood Cockroaches (family Blattodea, Parcoblatta pensylvanica).  Wood cockroaches are truly accidental invaders; they won’t take up residence inside a home.


Wood Cockroach


However, termites and carpenter ants present a more serious concern.  Although it’s highly unlikely for firewood stored inside a home to give rise to an indoor carpenter ant infestation, and it’s impossible for termite workers to establish a new colony without a queen, finding them emerging from firewood should trigger further investigations.  Firewood stored outside in close proximity to the home should be inspected particularly if the firewood is positioned right next to a home.


Carpenter Ant


The take-home message is to not store firewood inside a home.  Store it outside and only bring small quantities inside the home as needed.  Long-term storage of firewood should be positioned a distance away from a home.