Question

We need your advice desperately! We’ve lived in our new home for 3 months now. About three weeks ago, we started seeing these really tiny beetles everywhere. They’re in almost every room and they fly to lights at night. They’re driving us crazy and we can’t figure out where they’re coming from.

Answer

This is a sawtoothed grain beetle.

I can’t give you a definitive answer without seeing a specimen, but you could be dealing with a type of fungus beetle that is a fairly common (and temporary) invader in new construction. There are at least two different groups of beetles that feed on microscopic fungus growing on new building materials. Foreign grain beetles and plaster or mold beetles can build up to high numbers in new buildings where wood is still “green,” and plaster, drywall, and wallpaper are still damp. Accumulations of sawdust behind walls can also grow mildew, as can the paper backing on insulation. Often, you can’t even see the mold but you can detect a musty smell.

Although it can be found in stored foods, the foreign grain beetle is actually feeding on mold growing on damp grain. It also feeds on mold growing on any other surface such as wood or other building materials in a home. There are also several species of plaster or mold beetles that are found most often in new homes in wall voids where they feed on mold spores. The silken fungus beetle and the minute brown scavenger beetle are two more fungus-feeding beetles found in new homes. All of the fungus beetles are more of a problem in summer, and especially in humid parts of the country.

Unless your new home has moisture issues from a source other than damp construction materials, like a leaky roof, the infestation is self-limiting. For all fungus-feeding pests, as the structure dries out, the fungus will dry out, and the pests will die out. Unfortunately, this can take a long time, although you can speed up the process with fans and dehumidifiers, by running the furnace, installing vents, and by opening up voids to let them dry. If the outside air is drier (lower relative humidity) than the inside air, open windows and use fans to ventilate the structure. When outside air is humid, close windows and use air conditioning or heat, along with fans and dehumidifier, to dry out the inside.

If the beetle infestation doesn’t gradually disappear over a few months, it may mean that there is a more permanent moisture problem that needs to be corrected like poor drainage, a roof leak, condensation issues, or a wet basement. In this case, the beetles may be a yearly problem, almost disappearing during winter months only to reappear in numbers again during warm, damp weather.

Give us a call. We can determine whether your beetles are indeed fungus beetles and we can advise you on moisture control measures that eliminate pests. There are insecticide dusts that can be blown into voids that can provide some relief from fungus beetles until your home dries out.