The ABC's of stored-product pest management

by Meyer Sosland
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Stored-product pests flock to grain processing environments like proverbial "moths to a flame" thanks to the copious amounts of grain (food) sources available. In fact, the Indian meal moth is one of the most common stored-product pests in grain facilities.

Though Indian meal moths and other stored-product pests, such as flour beetles and granary and rice weevils, are tiny, they can create large problems for grain processors, because they contaminate much more than they eat. An infestation that begins in one product can quickly damage product throughout the facility if not immediately isolated and removed. In addition to destroying your grain or milled products, some storedproduct pests can even alter the flavoring of products through chemicals they secrete or cause allergic reactions if ingested.

Stored-product pests are classified into four groups based on their habits and biology: internal infesting insects; external infesting insects; external scavengers; and external secondary pests.

Internal infesting insects lay their eggs inside the kernel of the grain, and the larvae then eat their way from the inside out. External infesting insects eat from the outside of the grain into the kernel. External scavengers only feed on broken or damaged grain, while external secondary pests eat damp and moldy product.

Let’s take a look at two common stored-product pests in grain processing facilities.

The granary weevil is dark brown and ranges in size from 3 to 6 millimeters (1/8 to 1/4 of an inch) long. Also called a "snout weevil," the granary weevil uses its long, slender snout to break into the kernel and lay its eggs on the inside.

The internal infesting larvae of this insect and related weevils typically feed on wheat, oats, rye, barley, rice and maize, and also can threaten the safety of products by carrying harmful bacteria such as E. coli. Granary weevils typically live seven to eight months as an adult, and females can lay 50 to 250 eggs in their lifetime.

The Indian meal moth is an external infesting insect that is found worldwide. Females lay 100 to 400 eggs, often in clusters that hatch within a few days. Mature larvae measure approximately 8 to 12 millimeters long and vary in color, from dirty white to pink to green, depending on their diet. As adults, Indian meal moths can be identified by their "two-tone" coppercolored wings.

Indian meal moth larvae, not adults, actually cause the damage to products due to both their feeding activity and the silk web trail they leave when they move. These pests feed on a variety of grains, as well as dried fruits and chocolate.

The best stored-product pest control programs follow an Integrated Pest Management (IPM) approach. IPM programs emphasize proactive techniques to prevent pest problems and rely upon accurate identification of pests for proper treatment selection. Work with your pest management professional to follow these three steps to stored-product pest management success:

1) Be proactive.

Most stored-product pest infestations occur because the pests arrive in product shipments, the product is in poor condition, or sanitation issues in the facility allow them to breed and multiply. Take the following steps to help prevent stored-product pests from infiltrating your facility:

• Carefully inspect every product that comes through the door for signs of infestation, including webbing, damaged grain, pest larvae, or live or dead pests. Refuse damaged or infested shipments.

• Label and rotate products on a first-in, first-out (FIFO) basis to use the oldest supply first. Do not store materials for extended periods.

• Keep samples of all products in labeled jars and immediately dispose of any product if the sample shows signs of infestation.

• Eliminate sources of moisture in storage areas and keep the area well ventilated to prevent product from spoiling

and becoming susceptible to infestation.

• Immediately clean up spilled grain or other spills. Keep storage areas cool. Most stored-product pests cannot survive (or will develop slowly) in temperatures cooler than 65 degrees F (18 degrees C).

• Store products on wire, openbacked shelves positioned away from the wall and off the floor.

• Use pest monitoring devices like pheromone traps to monitor for storedproduct pests. Pheromone traps, which utilize synthetic versions of the chemicals pests use to communicate to draw pests to a sticky glue board, can help track trends in the frequency and amount of stored-product pest activity in your facility. These traps are available for both bulk grain storages and warehouses.

2) Be quick.

Since stored-product pests can reproduce rapidly, immediately dispose of any potentially infested product. Inspect the product surrounding the infestation for signs of damage, and quarantine the area/product to prevent further destruction.

Work with your pest management professional to identify the cause of the infestation, and take steps to eliminate the pest and remedy the problem.

3) Be team oriented.

Partnership between the pest management provider and facility staff forms the foundation of every successful IPM program. Ask your staff to assist in the monitoring efforts and immediately report pest sightings in a logbook for your pest management professional to review.

In addition, ask your staff to alert you to any conditions, such as broken air handling units, product residues in machinery, open packaging or spilled product, which could facilitate an infestation.

Immediately communicate any concerns to your pest management professional and work together for quick resolution.

With an ongoing IPM program, your facility can take down stored-product pests before they damage your products and reputation.

Patrick Copps is technical services manager for Orkin’s Pacific Division. A board certified entomologist in urban and industrial entomology, Copps has more than 30 years experience in the industry. For more information, he may be contacted at or visit