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Foreign Grain Beetles

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Despite the common name, foreign grain beetle are fungus feeders. Foreign grain beetles are mainly encountered indoors in the fall, especially when cold weather approaches and rainfall increases

Foreign grain beetles are mainly encountered indoors in the fall, especially when cold weather approaches and rainfall increases. Foreign grain beetles are also known to enter new homes during construction to feed on the mold, thus the nickname, “new house bugs.” Once indoors, foreign grain beetles do not bite or cause any structural damage, but they may spread pathogenic organisms, such as Salmonella.

Known Issues

  • Contaminates Food
  • Difficult to Eradicate
  • Structure Invading

Active Seasons

  • Fall

Foreign Grain Beetles Treatment Options

One-time Fall Invader Control

Adam’s licensed, Pest Management Professional (PMP) applies a proven, residual insecticide around the outside of the structure, under siding, in cracks and crevices, around the foundation and overhangs. Inside, Adam’s treats cracks, crevices, voids, and breeding sources, as well as the areas where the foreign grain beetles are most often seen.

Premier Fall Invader Prevention

Adam’s premier fall pest service provides year-round control of foreign grain beetles and other “fall invaders.” An EPA proven residual insecticide is applied to the foundation and exterior of the structure. Special attention is given to potential entry points, such as eaves, doors, windows, any cracks and crevices, and the sunny sides of the structure, typically the S and SW sides. Treatments are generally done in late August or September. The Premier Fall Invader Prevention service is an ongoing annual service, so you never forget to schedule treatment. The service is warranted for 12 months.

Premier Perimeter

Need to prevent more pests than just foreign grain beetles? Adam’s Premier Perimeter Program includes a minimum of 3 preventive barrier treatments around the exterior perimeter of your home for year-round prevention of common household bugs, including insects, spiders, and boxelder bugs. Your Pest Management Professional inspects for pests, and then applies a season-specific, non-repellent, residual material to control common household pests before they can get inside. Comes with a 12-month guarantee.

Premier Home Pest Prevention

Adam’s best value for prevention and control of common household pests, including foreign grain beetles! Adam’s Premier Home Pest Prevention service provides year-round pest prevention with a minimum of four visits throughout the year. Service visits focus on the exterior of your home, where most pest problems originate. And should a pest problem ever occur between scheduled visits, the plan includes additional treatments at no additional charge. This program includes common household pests like spiders, centipedes, sow bugs, and roaches and seasonal pests like wasps, multicolored Asian lady beetles, ants, and mice, as well as foreign grain beetles.

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More About Foreign Grain Beetles


  • While relatively small, foreign grain beetles are noticeable.

  • They are attracted to light and may be seen flying around light fixtures and windows.

  • Owners of new homes may become aware of an infestation when the foreign grain beetles begin to come out from under baseboards.


  • Foreign grain beetle adults are reddish-brown in color

  • They are about 1/8” in length.

  • Foreign grain beetles have a 3-segmented antennae club.

  • The distinguishing characteristic of the foreign grain beetle adult (when observed under magnification) is the presence of a tiny knob or bump on each of the front corners of the thorax.


  • Foreign grain beetles do not bite or cause any structural damage, but they may be a potential reservoir of pathogenic organisms, such as Salmonella (Spencer & Jespersen, 1998).

  • Besides being a nuisance, foreign grain beetles may generate liability issues in sensitive locations, such as food processing or handling places, hospitals, etc. Therefore, early detection and management of this pest is critical.


  • In late summer or early fall, adult foreign grain beetles fly from the fields, especially corn fields, and enter buildings seeking protected places to spend the winter.

  • They can enter your home through open windows and doors.

  • Being strong fliers, foreign grain beetles will spread to all rooms of the house.


  • Foreign grain beetles thrive on moldy growth on spilled grains, damp stored grain, musty cereal products, or molds on bins inside warehouses, mills, and food-handling facilities.

  • Foreign grain beetles have also been reported feeding on moldy pallets inside wrapped nonfood grade items.

  • Newly constructed homes often get wet from rain or snow during construction. As a result, mildew or mold can grow inside the home on rafters, joints, and studs. Foreign grain beetles are known to invade new homes during construction to feed on the mold, thus the nickname, “new house bugs.”

  • A humid bathroom can also provide a suitable environment for foreign grain beetles to thrive.

  • Foreign grain beetles can be attracted to older buildings in damp basements, around rotting windowsills, under moldy wallpaper, and on moist surfaces near leaky faucets.


  • Foreign grain beetles undergo a complete metamorphosis, in which there are four distinct stages: eggs, larvae, pupae, and adults.

  • The lifecycle lasts two to four weeks, depending on the temperature and relative humidity.

  • Female foreign grain beetles prefer to lay eggs in places with fungal growth capable of supporting larval development.

  • Eggs hatch in four to five days.

  • The larval stage lasts about 15 days and the pupa stage lasts four to seven days.

  • The lifespan of adults depends on the sex and mating status. Mated males and females of foreign grain beetles live an average 159 and 208 days, respectively; while unmated males and females live 275 and 301 days, respectively. (Menter & Mills, 1975)