Keep looking

Cigarette and drugstore beetles can be some of the most frustrating pests to deal with. Aside from putting out pheromone traps to try and pinpoint the origin of beetles in the house, and a good initial inspection, much of the work will have to be done by your customer.

A recent email from Devin Osborne of Osborne Pest and Turf in Austin, TX illustrates the problem. A new customer called with a persistent problem of small brown beetles he thought were emerging from an old headboard.  Rule number one: Don't assume the customer is right when it comes to diagnosing a pest. For insect identification nothing beats a good microscope or hand lens and ID guides. And keep an open mind about the likely source of an insect problem regardless of the customer thinks. 

Devin did trust his field guides and experience, and diagnosed the problem as drugstore beetle. The question remained, where are they coming from? A good PMP knows that no amount of insecticide spraying can solve a stored product pest problem.  Getting to the source is essential.

The customer took Devin's advice and went through "everything from grain to leather". The only real clue was that they only showed up in the adjoining master bedroom, master bathroom and closet.  Other rooms in the house appeared to be pest-free.  Rule number two: Don't assume it is not a stored product pest just because it's not in the kitchen.

A perfect protected feeding place for drugstore
beetles.  

Hot Booties contain linseed, one of many possible
foods for cigarette beetle.  

Eventually, after encouraging the customer to keep looking--success. An old pair of slippers called "Hot Booties" were suspicious. After googling the manufacturer, the customer learned that the booties (designed to be put in the microwave to heat for toasty tootsies) were full of linseed.  Rule number three: Exercise extreme caution when googling "hot booties".  Children should probably not be present in the room when you do.

Of course linseed is a type of grain, and any grain or seed or meal is fair food for stored product pests like drugstore beetle. In fact, any type of spice (paprika is a favorite), grains, nuts, seeds, breakfast cereal, bread, pet food, even some drugs can be food for cigarette and drugstore beetles.  These two species are some of the least discriminating stored product pest feeders.

Other situations to look for:

• taxidermy
• old rodent bait packets or stations
• old kid's art project
• accumulations of dead insects in lights
• chili pepper decorations
• cigars and cigarettes
• furniture stuffing
• potpourri 

And when the homeowner insists that there is no food source nearby, tell them to keep looking.  If you have any unusual places you have discovered stored product pests, I'd love to hear them. Just add a comment in the comment section below.

Tiny insects tell stories

A variety of beetles with similar feeding behaviors, sometimes collectively
called "plaster beetles". Drawing from Mallis Handbook of Pest Control.
These are tiny beetles ranging in size from 1-3 mm.

Who doesn't love a story?  Humans are suckers for narratives, so it's natural we should be interested when insects have their own stories to tell.  Especially when they are tiny insects that come from, seemingly, out of nowhere.

Among the insects I've been seeing lately are a group of beetles historically called "plaster beetles" or "mold beetles".  Though no longer a very accurate moniker (since joint compound has mostly replaced plaster in construction), plaster beetles feed on the fungi and mold spores found on building materials (including plaster and gypsum) after being exposed to rain and humidity during construction. The most common plaster and mold beetles come from the families Lathridiidae and Cryptophagidae (the Latin translation of which means "hidden feeders"). According to Smith and Whitman in the NPMA Field Guide to Structural Pests, these beetles can also become serious pests in otherwise squeaky-clean pharmaceutical, food manufacturing, canning and bottling facilities.

In Frank Meek's chapter on occasional invaders in the Mallis Handbook of Pest Control, he notes that the life cycle of plaster beetles can be completed in as little as 13 to 28 days.  That's pretty fast for an insect, and it explains how hundreds or thousands of tiny beetles can "suddenly" appear, coming from the walls and flooring of new homes. These beetles can also show up in older homes when moisture and high humidity occur.

Tiny (0.75 mm) beetle larvae swept up from a wood floor with
moisture "issues". The likely diagnosis is some kind of plaster or mold
beetle. Within weeks adult beetles will be infesting the home and
puzzling everyone as to their identity. 

I have always wanted to see (but never have seen) the immature stages of these beetles feeding in walls on building materials; and I've never heard of anyone else having seen them either.  Our deductions about what plaster and mold beetles are doing indoors are based on these beetles' biology, what they are known to feed on, and accounts of when and how the adult beetles appear. 

I recently received a sample from a PMP that comes close to providing "smoking gun" evidence for how these beetles come to infest buildings.  The sample consisted of thousands of the tiniest larvae swept up from a wooden floor (see picture).  As expected, the floor reportedly had moisture issues. Somewhere, hidden under the glued-down flooring of that home,  I imagined millions of "plaster beetles" breeding while feeding on mold spores and fungi associated with the slowly rotting wood.

Most plaster beetle problems can be solved by eliminating the source of moisture (and patience).  In new homes that were exposed to the elements during construction, properly designed and installed HVAC systems should eventually drive down humidity in the walls and floors. It may take multiple months, but eventually these beetles will disappear as molds desiccate and go dormant.

Wooden floors glued to concrete slab foundations pose a different challenge, as my wife and I learned the hard way.  We paid a contractor who assured us he had successfully installed many wood floors as glue downs on concrete slab foundations (the most common house foundation in our area). A few months after installation we noticed cupping and buckling of the new floor.  A moisture meter showed high (up to 20%) moisture in parts of the installed flooring. We had no water leaks under the house, but natural moisture exists under any concrete slab.  We got off relatively easily by pulling up all warped sections of flooring, putting down a chemical moisture barrier (usually epoxy or urethane based), reinstalling the wood and having the whole floor hand-scraped to hide further imperfections. Over ten years later we've not had any more problems, but I learned my lesson.  There are plenty of contractors out there who do not plan for moisture, and hardwood floors will fail because of it.

An unidentified cossonine weevil (2 mm) collected from a home with
moisture problems.  The presence of similar-looking beetles
should alert PMPs to likely moisture issues.  Note the elongated
face typical of weevils.

While we didn't have insects associated with our wood flooring, some do. Besides plaster beetles, another insect that can occur in wood floors is a group called the "wood weevils".  This is a name for beetles in the weevil subfamily Cossoninae.  I find little written about these weevils in the scientific or pest control literature, but have seen evidence from several homes where these beetles are associated with moist wood. In nature these beetles are found in damp and rotting wood--presumably the same resource that draws these beetles indoors. Unlike termites, these wood weevils don't seem capable of feeding on dry, sound wood; so treatment consists of solving the moisture issue and replacing the damaged wood. These beetles are most likely to be confused with powderpost beetles, so look carefully before diagnosing.

The next time you are faced with tiny beetles in a home that do not seem to fit the description of stored product pests, consider plaster beetles and wood weevils. They may be trying to tell you a story about your customer's home.