Stored Product Pests
Drugstore Beetle (Stegobium paniceum)
What do they look like?
The adult beetles are oval, about 1/10 to1/8-inch long and are reddish-brown in color. Fine hairs cover the body and rows of pits are seen on the wing covers. The head is bent downward and not readily seen from above. The antennae end in a 3-segmented club which differentiates drugstore beetles from cigarette beetles which have serrated antennae (see pictures at left). The larvae (seen below) are 1/6-inch, hairless, and cream colored with brown heads.
How do they get in?
Drugstore beetles are free-living in the environment and are good fliers. The adults are attracted to light and may be drawn to warehouses or homes which are lighted at night. They are also attracted to stored food products but may be brought into retail outlets (exchanges and shoppettes), food warehouses (commissaries), and homes in infested grocery products and dry animal food. Although drugstore beetles can fly, they are usually transported inside food packages. The beetles may also be found on the outside of pallets containing food products and between boxes and bags of food on palletized cargo. The increased use of airtight plastic or foil bags and pouches has significantly reduced pest infestations of stored products; however, drugstore beetles can chew through packaging in transit or during storage. Dry animal food is more susceptible to infestation since many packages are not “air-tight" and exhibit small openings which permit drugstore beetle entry.
Where do they live?
The beetles live inside the products, but adults will often leave the food to seek mates. Adult beetles are often found along window sills and interior walls. This may be the first indication that a warehouse is infested, but it will not indicate which products contain beetles or where infested products are located. Drugstore beetles are also found in spilled food in cracks, crevices, or seams on the floors in shipping containers, rail cars, and delivery trucks.
What is their life cycle?
The life cycle takes about 60 days to go from egg to adult, but may extend to seven months when temperatures are around 60 degrees Fahrenheit. Adult beetles can live up to 65 days. The adult female lays approximately 75 eggs. The adults can penetrate food packaging which allows this beetle to infest nearly all dry stored products in kitchens and pantries. If left unchecked, beetles from a single infestation can quickly spread to other susceptible products in warehouses, stores, or homes.
What damage do they cause?
Larvae damage food products through feeding and penetration of the packaging; the adult insects chew through packaging, including aluminum foil, to seek food. Adult beetles leave “shot-holes" in food packages when exiting the infested product. Drugstore beetles also infest dried flowers and other plant material. The adult beetles entering homes may be first attracted to dried plants and then seek stored food in kitchens and pantries.
Prevention methods:
Sanitation and inspection are the keys to good drugstore beetle prevention and control. Inspect pallets of food upon arrival at warehouses, and inspect individual products brought home from retail outlets. The presence of adult insects or holes in packages indicate infestations. Inspect salvage areas in food warehouses since spillage from broken packages is more common than in the storage areas. Check rodent bait stations weekly to ensure grain-based baits are not infested. Place food pallets at least 18 inches from walls to permit routine inspection and cleaning. Rotate food products so that older stocks are sold first; frequently inspect food with older manufacturing dates for infestations since adult beetles tend to emerge from packages in greater numbers as the infestation ages. This principle also applies in the home since beetles from a single infested product can migrate and infest multiple food products stored in a kitchen or pantry. Store dry food products in containers with tight fitting lids if the contents are not used within one week after opening
Control methods:
Sanitation and inspection are the keys to good drugstore beetle control. Pheromone traps are useful in determining if beetles are active in warehouses, but they will not indicate the location of infested products. Inspect pallets of food upon arrival at warehouses and inspect individual products when brought home. Adult insects or holes in packages are indications of infestations. Inspect salvage areas in food warehouses since spillage from broken packages is more common than in the storage areas. Check rodent bait stations weekly to ensure grain-based baits are not infested.
This principle also applies in the home since beetles from a single infested product can migrate and infest multiple food products stored in a kitchen or pantry. Store products susceptible to infestation in containers with tight fitting lids if the contents are not used within one week after opening. Place infested products inside plastic bags prior to disposal to reduce the spread of adult beetles. Segregate infested products in warehouses from non-infested products and cover with plastic until treatment or disposal. Place infested products in a freezer at 0 degrees Fahrenheit for four days to kill adults, larvae, and eggs. Do not reissue infested products or use for food preparation even after beetles are killed. Infestations can also occur when rodents are present. Mice will accumulate dry animal food, crackers, and cereal in harborage and nesting areas which may be inaccessible (behind walls or under cabinets). Rodent control and pesticide treatment in void areas may be the only way to eliminate beetle infestations in homes after efforts to inspect and locate infested products in kitchens or pantries have failed.
