Stored Product Pests


Bring out the ornamental corn and bean-filled draft stoppers – it’s fall!

We’re going to be discussing stored product pests – pests that feed on dried goods and food items, like bird seed, dried beans, dog food, pancake mix, cereal, rice, and chocolate. These pests can be a year-round nuisance because they live and breed within food in our temperature-controlled houses. They are very small and often go unnoticed until their populations are booming. Most of them generate enough water to survive simply by digesting food, so they can prosper in food that is almost devoid of moisture.

There are lots of stored product pests, but the most common two are the rice weevil and indianmeal moth.

The rice weevil is an internal feeder. Their tiny grubs live and feed within a kernel or seed, emerging only when they have reached adulthood. The adult weevil is quite small at around two millimeters in length, with a dark brown body and four lighter colored spots on its back. Weevils – also known as snout beetles – have elongate faces with what looks like a trunk or a “nose.” It is actually more akin to a mouth, since the mandibles are at the tip of the snout. They prefer seeds, corn, and rice.

The indianmeal moth is a surface feeder. The larvae, or caterpillars, are the damaging stage. The adult moth does not feed, although it will drink water. The caterpillars are flesh tone without any patterning, while the adults have wings which are half tan and half copper-colored. They attack a wide variety of food to include dog food, almonds, oatmeal, dried fruit, and spices. Infested foods are covered in silk and fecal pellets. When the caterpillars have grown large enough to pupate, they wander away from the food source and spin their cocoons in dry, sheltered areas.

Solving a stored product pest problem is straightforward. The source of the infestation must be found and eliminated. In many cases, there are multiple sources. Infested foodstuffs should be thrown away or frozen. Freezing is acceptable for items that aren’t meant for human consumption, such as dog food or wild bird seed. Most people cannot stomach the thought of eating small boiled caterpillars in rice, even though they cause no harm when cooked and eaten. (I have done it and lived to tell the tale.)

When throwing away infested foods, be sure to immediately discard them outside. Throwing away food inside can result in pantry pests emerging from your trash can and perpetuating the problem, especially if the trash sits inside for several days.

Some stored product pests – like the indianmeal moth – can fly and easily move an infestation around the house. Others, like mites, can only crawl, so an infestation will be confined to a single area or take longer to spread. Some stored product pests only eat mold and may indicate a moisture issue. For this reason, identification is important, although most problems can be solved by finding and discarding all infested items and placing all non-infested, susceptible items in airtight containers. As a preventative, you can freeze incoming goods that have a chance of being infested. I freeze all new bags of bird seed that enter my house – bird seed is often infested when you buy it.

Be sure to consider food sources that may not be for eating. Decorative corn, old rodent bait, bean bags and draft stoppers filled with real beans, bird seed, Rid-X®, and saved garden seeds are all susceptible to attack and may be less obvious than infested pantry items.