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From: Food Quality & Safety magazine, April/May 2007

Small Pest: Big Problem

Don’t Let Stored-Product Pests Damage Your Business

by Zia Siddiqi, Phd, BCE

Beetles crawling over counter tops, moths flying across rooms or caterpillars crawling up walls and across ceilings are all signs of big problems from small pests. To discount these pests as mere passersby would be a mistake, for the old saying “don’t judge a book by its cover” rings true with stored-product pests.

Although small in size, these pests can cause considerable damage. Worldwide, insects destroy about 10 percent of grain production each year. In the U.S., this figure translates into an annual economic hit of about $3 billion.

According to, it is virtually impossible to estimate how many pounds of food are destroyed each year because of various types of contamination, including that caused by packaging. The Food, Drug and Cosmetic Act of 1938, specifically the good manufacturing practices (GMPs) portion of the act that addresses pest management concerns, specifically defines destruction.

Section 402 (a)(4) of the act states that “food shall be deemed…adulterated if it has been prepared, packed or held under conditions whereby it may have been contaminated with filth or whereby it may have been rendered injurious to health.”

Insects and other pests are often drawn to a production environment because of warmth, water or the presence of food. Light also attracts pests.

Stored-product pests don’t feed solely on grains. They devour many types of food and contaminate much more than they eat. Even a small infestation can severely harm your inventory. In addition to affecting your bottom line with ruined commodities, stored-product pests compromise food quality and safety. Some species secrete chemicals that alter the flavor of food products, while others cause allergic reactions and irritate the human digestive tract if ingested.

Based on eating habits, stored-product pests fall into two major categories—internal and external feeding insects. Internal feeders, including granary and rice weevils, lay their eggs within the grain so that the larvae can feed on the inside the product. External feeders, such as Indian meal moths and cigarette beetles, prefer feasting on the exterior of the product. A third but smaller group includes scavengers, which eat the grain only after the shell breaks.

Let’s take a brief look at four common stored-product pests:

  • Granary weevil: Most commonly found in the northern region of the U.S., adult granary weevils measure 1/8- to 1/4-inch long and are uniform in color, typically – black or chestnut-brown. Despite the fact that their poorly developed wings hinder them from flying, they still feed ravenously on a multitude of grains. With an average adult life of 7 to 8 months, females can produce anywhere from 50 to 250 eggs during their lifetime.
  • Rice weevil: Rice weevils begin a 3- to 6-month lifespan growing entirely within the grain kernel. Slightly smaller than granary weevils, rice weevils average 1/8-inch long and are typically a dark reddish-brown color. Rice weevils can fly, which allows the adult females to deposit their lifetime output of 300 to 400 eggs.
  • Indian meal moth: Although only about 1/2-inch long when fully grown, large groups of Indian meal moths can cause severe damage to food supplies and equipment with the webbing they deposit. Adult Indian meal moths, easily identified by their two-toned, copper-colored wings – have a short lifespan (one to two weeks) – largely because they only feed during the larval stage. However, adult females still manage to lay between 100 and 400 eggs.
  • Cigarette beetles: Feeding on a wide variety of stored products ranging from dried flowers to powdered milk, these light brown, humpbacked beetles make the small amounts of food residue left in equipment their haven. Usually about 1/16- to 1/8-inch long, adult cigarette beetles lay 30 to 40 eggs during a lifespan of less 30 days.

Stored-Product Pest Management

Fortunately, there is a way to keep stored-product pests at bay. To protect your food supplies, commit yourself to a pest management program based on proactive operational measures and sanitation techniques.

Stop stored-product pests before they start with a first-in, first-out (FIFO) system. Write the date of arrival on the product packaging and then rotate out the items in the order received. Store all products on wire-back shelves off the floor and away from the wall to help prevent products from deteriorating and serving as prime breeding spots for pests. In addition, discourage pests by making the facility an uncomfortable environment for them. Stored-product pests cannot withstand extreme temperatures, so cool buildings to temperatures below 65° F and reduce humidity by keeping the environment well ventilated.

An effective sanitation program reduces the elements that attract stored-product pests to your facility in the first place. Clean up food spills immediately to prevent debris from accumulating in cracks and crevices, and keep the facility clean and dry. Implement simple steps, such as thorough vacuuming and careful garbage disposal, into your sanitation program to decrease chances of pest survival.

Inspect your facility regularly for signs of infestation (webbing, live larvae or adult pests), and remove the infested commodity immediately to prevent the problem from spreading. If appropriate, work with your pest-management professional to install pheromone traps in a grid formation to monitor and trap the pests. Remember, effective treatment relies on proper identification of the pests.

With preparation and an immediate response to an infestation, you can keep the problems caused by stored-product pests proportional to their minute size.

Dr. Zia Siddiqi is quality assurance director for Orkin, Inc. A board-certified entomologist, he is recognized expert in pest management with more than 30 years’ experience. Reach him at



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