Stored Product Pests

The Indianmeal moth remains the number one stored product insect pest causing customer complaints in stored products in North America and temperate regions around the world. Photo by Whitney Cranshaw, Colorado State University, Bugwood.org

Excerpted from “Reducing Customer Complaints in Stored Products” by David K. Mueller
 

From the time grain is harvested until it reaches the dinner table, pests seek stored products and cause customer complaints. In order to solve a customer complaint, it is important to know why the pest is there in the first place—What attracted it to that particular place in time and where did it originally come from? Insects are a symptom of a condition. The following excerpts from "Reducing Customer Complaints in Stored Products" by David K. Mueller take a look at some areas along the food chain that one may not think of as being attractive to or providing conducive conditions for stored product pests.

Packaging Material Storage. Most manufacturing facilities have a designated area in which to store packaging materials. These same companies often have excess paper stock stored in the vicinity that may remain indefinitely before it is used or discarded. This is a prime location for insect and rodent infestations to occur.

Psocids (or booklice) thrive in old paper stock. They are tiny and almost invisible to the naked eye. However, they can reproduce and become a source of customer complaints for manufacturers of food products.

Often the paper stock storage area has old labels and cardboard from products that have long been discontinued. As this old material accumulates, so does the potential for pests. Mice are always searching for nesting material. The paper material is shredded and used for nesting. Infrequently inspected areas lead to inviting conditions that pests look for to establish their safe domain. It is important to rotate stock in these areas, remove old and unused paper products, and continuously inspect around the pallets for signs of pest activity.
 

Canned Psocids A can manufacturer had had a recent customer complaint about its cans. Its customer found some very small white specks on the bottom of a few of these empty cans. The small white specks were identified as psocids. Their small moisture-filled bodies had fallen into the cans and died. The attempt to rid the cans of this tiny insect failed, and the vendor refused to take the “almost insect-free” cans that were being shipped to them. The psocids were living in the paper slip sheets between the cans. When the can manufacturer fogged the warehouse after the vendor complaint, more psocids dropped into empty cans, died, and dried up. A dead insect in a food product can be as bad as a live one.

Production Line. In addition to idle areas, insects are attracted to warm areas (not hot, but warm). If a motor inside a piece of equipment produces a heat source, insects will often migrate to these areas. Many times these motors are located in hidden places like a roll stand in a flour mill or near a dryer in a pet food or cookie factory. Motors like these are typically covered for safety reasons. The inspector or pest manager often shies away from a place that has moving parts, like a motor, because of the potential risk of injury. Crawling on hands and knees with a flashlight near a loud, greasy, high-speed motor is a less than desirable job and is often ignored. These areas escape inspection and are often in the same proximity to production or packaging.

It is important to watch the production line and look for defects in the packaging process. Spending time observing these areas of the manufacturing plant will help you understand how the product is made and why insects might prefer these areas. While observing, ask yourself the following series of questions: Is the machine producing too many units so the boxers cannot keep up? Does the packaging line spill product on the floor that is stepped on and becomes difficult to clean? What is the age of the improper piece of machinery that likely has been re-purposed many times? Modern equipment is costly but the investment often pays dividends in production and sanitation efficiencies.
 

Bugged Vents An Indiana manufacturer fills a small apothecary jar with popcorn for promotional fundraisers. The jar top is sealed and the cases of product fumigated before shipping. There were numerous customer complaints about the popcorn and the manufacturer could not determine the source. We found that the processing equipment vented to the roof and it was not cleaned regularly. Psocids were consequently falling into the product. The fumigation was not killing the insects because the fumigant did not penetrate the jars, as the lids were tightly fitted and had food safety security strips. The solution to the problem was a combination of several immediate control treatments, including the regular cleaning of the vents to the roof.

Transportation Trailers. Trucks that carry food from one location to another can be a source of infestation and potential customer complaints. Some companies have captive trailers that they use repeatedly. This offers direct care, custody, and control over the cleanliness of the trailer.

When inspecting a truck trailer prior to loading, it is important to thoroughly sweep the debris from the floor and edges. Stored product insects are commonly found hiding in the sidewalls. Carefully inspect the trailer with a flashlight for insect and mouse evidence behind these reinforced sidewalls. A good inspector can be able to detect the smell of some stored product insects and rodents. Inspectors can also detect insect or rodent evidence under the clear shrink wrap or on the product and blame the manufacturer.

Inspect trailers during daylight hours by shutting the door while inside. Especially look for light holes coming from outside. Poorly maintained trailers allow insects to enter and become a potential customer complaint. A grasshopper or house fly, found by the untrained receiver, may cause a rejection of the product by the receiver.

Refrigerated truck trailers, commonly called reefers, are sealed tight enough to keep frozen products frozen as they move around the country. Refrigerated trailers can have condensation issues that cause standing water. Even with drain holes, located on the bottom corners of the trailer, mold and product damage can exist due to water. When a trailer is found to have insects or mice, refrigerated trailers make excellent fumigation chambers. With the doors sealed and the drain holes plugged, the trailer becomes an ideal and safe fumigation chamber. Remember that truck trailers cannot be fumigated in transit.

Pests en Route [In the 1980s a government-sponsored grain storage program was created. While the program was beneficial to some, others who took advantage of the long-term storage program faced massive insect infestations of the grain.] Trains carrying food products traveled on the tracks adjacent to the government storage. Spilled grain was scattered along the train tracks. When spilled grain is near finished food, it often harbors grain insects, rodents, and birds feeding on this unprotected free meal. The mere presence of these pests near the food being transported offers a possibility for contamination. A fumigated rail car that leaves one location under gas will only retain the fumigant for three to four days. After the fumigant has dissipated, there is no residual activity from the fumigant. Any pest that detects the food product may enter the railcar and cause a complaint.

The author is owner of Insects Limited, Inc. He can be reached at dmueller@gie.net.