Collage with food in glass containers, with four bugs trying to get into stored products

Stored Product Insects: Still Celebrating the Holidays?


stored-product-pest-collageIt’s January—time to pack up the decorations and look ahead to a brand new year, right?  Yes, but in addition to storing your holiday items for another year, make sure that you don’t overlook the perishable materials.  Unfortunately, this time of year our customers may find themselves being visited by some very unwelcome six-legged guests in the form of stored product insects (SPI).  It should be no surprise, since in the last few months of the year we tend to purchase, prepare, consume, and decorate with countless items that can and often do serve as a food source for these insects. From decorative corn and chocolate treats to the perennial gift we love to hate…the fruit cake, we fill our homes and work places with a veritable SPI buffet.

Many SPI generally feed upon a wide variety of materials of vegetable or animal origin and can infest products at virtually any point in the product’s life, starting from the field and ending in the home or office.  Although SPI can migrate indoors, this time of year they are likely introduced on infested products.  Most SPI are polyphagous, meaning they can feed on many different types of foods; however they can’t always feed on all forms.  SPI are generally grouped based upon their feeding habits.  The 4 groups of SPI include internal feeders, external feeders, scavengers and secondary pests.

Internal Feeders

corn grainery pour

Internal feeders are insect larvae that feed within the kernels of whole grains or seeds, thus leaving behind a hollowed shell when they emerge as adults.  Examples of internal feeders include the rice and granary weevils, which are tiny beetles with long snouts and also small moths called Angoumois grain moths.  The Angoumois grain moth is often found emerging from the decorative ears of corn we so often use in fall decorations.  Though similar in size and coloration to the clothes moth, the hind wings of the Angoumois grain moth are pointed and fringed unlike the rounded hind wings of the clothes moth.

External Feeders

Don't let moths eat your clothing

External feeders develop outside of grain kernels and are capable of feeding on both whole and processed grains.  The Indian meal moth (IMM) is the most commonly encountered external feeder and the most common SPI in homes.  This moth is easily recognized by its two-toned forewings that are tan on the front third and reddish-copper on the back two-thirds.  If disturbed, adults fly in a very irregular zigzag pattern.  The larvae feed upon a wide variety of foods, including seasonal favorites like chocolate, dried fruits, crackers, nuts, and just about any other dried foodstuffs we line our tables and shelves with during the holidays.  Adding insult to injury, larvae leave behind their calling card in the form of frass-laden webbing over the surface of the foods they consume.


The next group of SPI, the scavengers, tend to feed on fine pieces of damaged or milled grain products and often arrive on the scene after feeding damage by other insects.  Sawtoothed grain beetles, and its nearly identical cousin the Merchant grain beetle, are tiny brown beetles that have saw-like projections on either side of the thorax.  This pest can be real menace to your holiday foodstuffs; they feed upon a wide variety of our festive goodies, including dried fruits and meats, sugar, chocolate, various nuts, seeds, and items of similar character.  To make things worse, their small size permits them easier access into packaged food items.

Also, their small size allows them to sequester themselves into the smallest cracks and crevices and go unnoticed for long periods, leaving ample time to build up large populations in a short span.  Flour beetles, of which the red and confused variety are the most commonly encountered, also show up on the scavenger most-wanted list.  These two reddish colored beetles are frequent scavengers of flour and grain meals which we commonly use to make our favorite seasonal cakes and pastries, as well as spices, dried fruits, and cereal products.  Like some of their scavenger compatriots, their small size allows them to easily penetrate into sealed foodstuffs.  It’s not just beetles we find among the scavengers.  The Mediterranean flour moth, the almond moth, and the raisin moth, each of them scavengers in their own right, frequently infest the types of products for which they are named.

Secondary Pests

Flat Grain Beetle

Secondary pests are those that prefer moldy materials that have sat around for some time.  In all of the hustle and bustle associated with the holiday season, all of those extra ingredients that were purchased for baking can leave a kitchen and pantry in quite a mess.  Be sure to check beneath shelves and inside cabinets to clean up any spillage, and also ensure that any left-over raw ingredients are properly stored.  If not careful, our customers may find themselves dealing with spider beetles, psocids, and flat grain beetles, just to name a few.

During the holiday season, SPI can occur in many different places and situations. While we are keenly aware of the usual hot spots, some additional considerations for infestation during the holidays include dried flowers, wreaths, potpourri, and toys stuffed with grain kernels.

Fortunately for our customers, SPI problems can be remedied in large part by practicing good sanitation, inspecting and identifying the source of infestation, and removing any infested materials.  In addition, we recommend to our customers that foodstuffs be stored in tightly sealed containers.  This way, we can help to reduce the likelihood that items become infested and also contain infestations that are already occurring.  Armed with this knowledge and coupled with our technician expertise, we can keep our customers happy and provide relief from unwanted invaders as we move full speed ahead into 2014.

For more information about different stored insect species, explore our Insects Found in Food Pest Guides.

Do you have any stored product insect questions? Ask away in the comments below! 

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Dr. Nancy Troyano

Nancy Troyano, Training Manager / Entomologist at Rentokil North America, is responsible for leading and supporting the development and training of Rentokil technicians throughout North America. Nancy works closely with Technical Field Trainers and Line-of-Business Managers to develop and implement a comprehensive training program for new and existing technicians. Nancy joined Rentokil after receiving her PhD from Virginia Polytechnic Institute and State University (Virginia Tech) in 2009. Follow Nancy on Google+

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