The two most common beetles affecting stored grain products are the red flour beetle and confused flour beetle. These species prefer warmer climates but survive Canadian winters in temperature controlled granaries, farms, and warehouses.
These species of flour beetles look almost exactly the same. They are shiny, flat, reddish-brown insects about 3-4mm long. The larvae of both species also have the same appearance. Both are white with hints of yellow, 2 prominent dark processes at tip of abdomen. The larvae of the red flour and confused flour beetles can grow up to 6mm in length before pupating.
Both the red and confused flour beetles infest grain and grain products worldwide. They are commonly found in stored grains within mills, warehouses, supermarkets, and homes. In homes, these pests can thrive in crevices inside pantries and kitchen cabinets where food spills infiltrate.
These beetles feed on finely milled starches such as flour or meal. They do not feed on whole or undamaged kernels and need ground grain to survive.
The average lifespan of an adult flour beetle is about one year. Females lay about 450 sticky, white eggs directly onto a food source. This tacky exterior of the eggs collects fine particles and broken grain, which coats and protects them until they hatch. Larvae then feed on the surrounding food until pupating and emerging as adults.
Problems Caused by Flour Beetles
While their feeding causes some damage to food products, the worst issue with flour beetles comes from contamination. During an infestation, dead beetles, cast off skins, fecal pellets, and liquid waste pollutes whatever product the insects have invaded. Live flour beetles also cause moisture to build inside stored items, which can lead to mold growth.
Detection/Signs of Infestation
An obvious sign is seeing the adult beetles crawling around an infested product and/or lumped food particles formed by larvae. A sharp, unpleasant odour coming from stored flour or cereal may suggest a flour beetle infestation. Severely infested milled grain can also appear pink due to the sheer number of insects.
The best way to prevent flour beetle problems is to inspect purchased cereals, flour, cake mixes, and noodles before storing them in your home. Transferring all milled grain and starch products to airtight containers can also keep infestations from taking hold and inspect pantries regularly for pest activity.
If a food product is heavily infested, the best method of control is to discard infested items. Light infestations can be controlled by temperature manipulation, either freezing or heating when applicable.
Always clean up spilled flour/food products, especially in hidden areas around appliances. Vacuuming pantries and cabinets while paying close attention to cracks and crevices is another effective way to keep flour beetles from infesting stored food.