PLASTER BEETLES AS A RESULT OF NEW CONSTRUCTION

By Chris Williams on July 17, 2017.

Over the past week we’ve seen quite a few tiny insects on the walls in our new townhouse. We’ve been told that they are plaster beetles but no one seems to know anything more about them. What do they do? C. G., Jamaica Plain, MA

We’ll assume they are plaster beetles, but know that these tiny beetles (only 1/20 inch long) that feed on mold are easily confused with tiny beetles that infest stored foods and with other tiny beetles. It really takes an entomologist and a microscope to correctly identify them. Of course if you find them in association with moldy materials that’s a big clue.

These beetles in the family Lathridiidae are commonly called plaster or mold beetles and there are several species that can become nuisance pests in homes. Some of them can fly. Plaster beetles are found in damp areas where both the adult beetles and the larvae feed on fungi and mold spores growing on various surfaces. They can even be found in food packages or bulk food bins but they are not feeding on the food, instead they are feeding on a layer of fungi growing on the food.

MOLD CAN GROW ON DAMP BUILDING MATERIALS

We often find plaster or mold beetles in association with new construction or renovation where they infest building materials that are “green,” not yet dried or cured, or got wet during the construction process. This can include damp lumber, plaster, or damp wallpaper or wallboard. In fact, the plaster beetle got its name when walls were constructed of wire netting filled with plaster, back in the 1930’s to 1940’s. The beetles were found feeding on surface mold growing on the still wet plaster.

Even when not associated with new construction, plaster beetles can infest homes when there are plumbing or roofing leaks, floods, or heavy condensation that keeps areas damp and subsequently grows mold. The beetles can also be found infesting damp food products such as moldy breads or grains, or moldy plant material. They become pests most often during warm weather in the wet season or in hot summer weather when humidity is high.

DRYING OUT THE SITE WILL KILL THE MOLD AND THE BEETLES

Plaster beetles can’t survive in low moisture conditions, largely because when the humidity is low, mold doesn’t grow. The key to control of the beetles can be as simple as drying out the damp area to less than 20% relative humidity with fans, dehumidifiers, or by raising the temperature. Drying out large areas of new construction is a bit more complicated and can take a long time in the summer, even with dehumidifiers, to reduce humidity in wall voids. You may need insecticide treatment to kill emerging beetles in the meantime.

Give Colonial Pest a call so that we can inspect your home and identify the insects in question (save a few if you can). We can track down areas with mold growth and can assist you in drying out or treating the site.

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