The foreign grain beetle, Ahasverus advena, is a small and flattened beetle about 1/12 inch (2mm) long. It is reddish brown and has a three-segmented antennal club. The key identifying character is the sharp points at the front, outer edges of the prothorax.
In most areas, foreign grain beetle is of minor economic importance as it only attacks grain products that are moist, moldy and out-of-condition. Food products attacked include cereal grains, flours, beans, dates, figs, biscuits, yams, tobacco, cocoa, ground nuts, copra and palm kernels. Being strong fliers, the tiny foreign grain beetles spread to all rooms of the house.
Fortunately, the molds in the walls are not damaging to the wood and will soon die after the wood finally dries out. This may take one to three years depending on the climate of the area and how much moisture was initially introduced into the wall voids. After the mold dies, the foreign grain beetles also die, however, treatment will be necessary in those situations where the beetles are invading the home’s interior. This same phenomenon may also be encountered in older buildings or other buildings where poor ventilation, water leaks or poor drainage create conditions promotimg fungal and mold growth.
The biology of the foreign grain beetle is not well known. It can complete the cycle from egg to adult in as little as 30 days and does not breed at relative humidities below 65%. Under optimum environmental conditions, huge populations can quickly build up, pushing the beetles out of the breeding source in search if fresh materials. The beetle is commonly a pest in newly built homes where it appears within the first one or two years. When a home is being constructed, rain and moisture may fall onto exposed beams prior to the roof and walls being added. If enough moisture has accumulated on the wood, surface fungi may grow on the studs inside the wall. Foreign grain beetles, being present in nature, may find some of these homes, enter the walls, and begin feeding and breeding on these surface molds. After a period of many months, the populations of these beetles within the walls grows large and beetles begin to emerge by the hundreds from under baseboards, from behind electric outlets and from around light fixtures in ceiling. Larva may also be found on floors near baseboards where adult beetles are found.
Foreign grain beetles will be found in moldy, moist and out-of-condition grain products or in walls, crawlspaces or attics were excessively moist conditions allow the growth of molds and fungi. Inspections will need to be focused on identifying sites where fungi and mold could be allowed to accumulate. When inspecting grain or other food products, move grain about with a screwdriver or a knife and look for adult beetles. If a homeowner reports seeing hundreds of tiny beetles suddenly on floors, inquire as to the home’s age. If the home is only one or two years old, it is very likely that foreign grain beetles are the culprit. It is a good idea, however, to confirm the identification using a magnifier prior to enacting control efforts.
When foreign grain beetles are found infesting grain or food products, these should be cleaned up and or/ discarded because they are likely moldy and unfit for consumption. Treatments if cracks in those areas with a residual insecticide may be needed in case adults or larvae are harboring there. Spot treatments using an appropriately labeled residual insecticide also can be made to surfaces where these beetles might crawl. When foreign grain beetles are found infesting a new home, all wall voids in rooms where beetles are found should be drilled and treated using a residual dust insecticide. If available, the walls may also be treated with residual liquid insecticide. Wall voids where electric outlets are located do not require drilling as the insecticide can be applied into the void after removing the cover plates to the outlets. Apply a residual dust insecticide under the edges of all baseboards and under the edges of all carpets. Instruct the homeowner to seal cracks, around light fixtures, vents, ceiling fans, etc. that penetrate the ceiling. Spot treatments may also be applied using an appropriate labeled insecticide along baseboards in infested rooms. Beetles on floors, window sills, counters, etc. should be removed using a vacuum device.
Adult beetles may continue to be seen after these control efforts. Advise the homeowner of this fact but assure them that the numbers will be greatly reduced and the numbers seen should be minimal. Infestations of this type might possibly reappear the next year, but the instances of more than one year of foreign grain beetles appearing in a new homes are not common.
When these beetles are found in old buildings or homes that are older than several years, high-moisture conditions are present that are promoting fungal and mold growth on which the beetles are feeding. In these cases, long-term relief will only be achieved by addressing the causes of high-moisture conditions: water leaks, poor ventilation, etc. Additional foundation under/ or attic vents may be needed and poor drainage along the foundation may be necessary. Water leaks need to be repaired and moist voids or wood need to be dried out using fans. Damp basements may require a dehumidifier. Any treatments applied without correcting high-moisture conditions are likely to fall. If the voids where the foreign grain beetles are living can be identified, these can be treated described above for these beetles in homes.
If beetles are found crawling about beams in a crawlspace or attic, temporary relief may be provided by applying spot treatments to those surfaces using appropriately labeled residual insecticides. |
