Most recently reviewed by: Pat Porter (2018)
Common Name(s): Merchant Grain Beetle, Sawtoothed Grain Beetle
Two of the most common grain beetles are the sawtoothed grain beetle Oryzaephilus surinamensis and the merchant grain beetle Oryzaephilus mercator. Virtually identical, sawtoothed and merchant grain beetles are around 1/10 inch long with flattened bodies well-adapted to crawling into tiny crevices. The name, Sawtoothed, is derived from the saw-like projections of the pronotum. The larvae of both species are less than 1/8 inch long and feed on broken grain and products made from processed grain.
The sawtoothed grain beetle does not fly and is not attracted to light, whereas the merchant grain beetle does fly and prefers light.
Origin and Distribution
The sawtoothed grain beetle is the most commonly encountered pest in grain and grain products, and will feed on any foodstuffs of vegetable origin. Broken grain kernels and “fines” are the principal food source, and intact kernels are not suitable as egg laying sites. The merchant grain beetle is also commonly found in grain but prefers oilseeds, including nuts.
Habitat & Hosts
These beetles are often present in high numbers in grain storage facilities. They also like to attack cereals, cake mixes, macaroni, pet food, cookies, and chocolate. They are small enough to easily penetrate tiny cracks and crevices in packaged food products.
The life cycle (egg, larva, pupa and adult stages) is short, producing six to seven generations a year. Adults live an average of six to ten months, but some can live three years.
ManagementIf you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.
Thorough inspection is needed to discover the source of grain beetle infestations. Problem areas should be inspected frequently to discover stored product pests before infestations flourish. Spilled food and grain products such as flour and cereal behind and under shelving can be a source of infestation. Sanitation and proper storage of grain products help prevent and control grain beetles. Temperatures below 0 F for 24 hours will kill all stages of grain beetles. Although detection and elimination of infested product is the key to controlling these and other stored product pests, crack-and crevice applications of appropriately labeled insecticides are sometimes warranted.