Facts, Identification & Control
Plaster beetles are members of the family Lathridiidae. They are very small insects, usually less than 1 to 3 mm long. The color ranges from yellowish brown to reddish brown to almost black.
Behavior, Diet & Habits
Plaster beetles feed on mold and fungus. They got their name when many homes had plaster walls. Mold often grew in new homes inside walls or under wallpaper while the plaster was drying. The beetles fed on the mold inside of walls. Homeowners would discover the beetles when they came out from under the baseboards. Some people call these insects minute brown scavenger beetles or mold beetles.
Plaster beetles feed on mold, mildew and other types of fungus. There must be dampness or high humidity for these beetles to thrive. Most of them live outdoors. They live under tree bark, under logs and rocks, and even in bird nests.
Indoors, they live in damp basements and crawlspaces. They have also been found on cheese, fruit, and damp fiber and carpet. Wet straw and wet structural lumber can support mold and mildew that these beetles eat.
Plaster beetles sometimes appear in homes after a period of heavy rain. Some species can fly and are attracted to light. When they gather at windows, they can cause distress to residents.
Eggs are deposited by females near the fungi food sources. Larvae hatch and begin to feed on the mold spores. Eventually, they attach themselves to a surface and pupate into adults. Development time varies and can be as short as about a month to over five months depending on temperature and food availability.
Signs of a Plaster Beetle Infestation
Most often, homeowners detect plaster beetles by finding the beetles on surfaces or attracted to lights. Due to their small size, they can be difficult to identify without the aid of magnification.
Controlling plaster beetles starts with moisture control. It is very important to eliminate the dampness that supports the mold or mildew. Search out and repair plumbing leaks. Make sure that gutters and downspouts drain away from the foundation. Unblock crawlspace vents so that air can circulate. A dehumidifier may be necessary in a damp basement.
The next step is to close up any entryways that the beetles might use to get into the home. Exterior doors should close tightly. Replace weather stripping that is damaged or missing. Check the screens on windows and crawlspace vents.
If any adult beetles are inside the home, a vacuum cleaner can remove them quickly.
An insecticide barrier outdoors can help prevent plaster beetles from entering. The barrier will need to be reapplied periodically. The local pest control professional can apply liquid or granular insecticides as needed.