The Wrap on Stored Product Pests

Packaging is as important as any other component of a product. For consumers, packaging can be a major deciding factor in their purchasing decision. For those in the packaging industry, it is a way to protect and preserve the product. That said, the complete package here doesn’t have room for stored product pests.

A variety of packaging materials such as polymer, aluminum foil card box and paper can be penetrated by pests, though the extent of penetration depends upon the type of pest. Some insects have the ability to chew through packaging materials to access the product inside—these are referred to as penetrators.

Others pests are opportunistic and take advantage of imperfectly sealed packages and points of weakness in the packaging such folds, seams and air vents.  These insects are lured in by food and warm conditions often found in a commercial facility or warehouse. Proper packaging using insect resistant packaging techniques and materials is the first step in managing stored product pests.

Stored product pests can infest and damage a wide variety of products. While much of the damage usually occurs in storage, infestations may originate where the materials are produced or processed, during shipment, in storage or in the area of use.

Stored product pests such as grain weevils, Indian meal moths or sawtoothed and merchant grain beetles thrive on grains and grain products. These hungry pests can cost a mill, bakery, food processing facility or a restaurant thousands of dollars in contaminated goods. For example, the extensive webbing of Indian meal moths can block milling equipment. Even worse, they can jeopardize a company’s compliance with government regulations, potentially stopping operations altogether.

A tobacco leaf showing damage caused by a Cigarette Beetle.

One reason stored product pests can cause so much damage is that they contaminate much more than they eat, meaning even a small infestation can have a significant impact on final product output.

Here is a list of the most common stored product pests and signs they might have infiltrated your facility.

Indian Meal Moths are the most common pantry insect pest. These insects feed on a large variety of stored food products including pet foods. An infested product will have silk webbing on thew surface of product and packaging. Moth droppings, known as frass, can be seen inside the product. Another obvious sign is seeing larvae moving about in product—they are dirty cream-white in color, with the mature ones measuring about 15-millimeters. When they are about to pupate, they may leave the infested product and hence be noticed wandering around in the storage areas, especially on walls or racking. The larvae have the ability to chew and penetrate packaging. Sticky pheromone traps available in stores can be used for detecting and monitoring Indian meal moth activities and population, to help identify areas of high activity.

Dermestid and Trogodema Beetles tend to feed on a variety of products such as flour, cereals, candy, cocoa, cookies, corn meal, nuts, pasta and dried spices. The mature larva on average is about six-millimeters long and can be seen feeding and moving around in the infested product. Only the larvae feed on food. Some species of this beetle, such as carpet beetles, will also eat fabric, meaning infestations can spread from food to clothing and have costly and damaging consequences.

Sawtoothed Grain Beetles are very small beetles, about 2.5-millimeters long, flat and brown in color. Because of their size and shape, they are able to invade imperfectly sealed packages. They are scavengers and prefer processed food products like bran, chocolate, oatmeal, sugar and macaroni, though they do not attack whole grains. These pests can burrow their way right through boxes and packaging, putting other sealed foods at risk for infestation.

Cigarette and Drugstore Beetles are also small brown beetles, about two- to 3.5-millimeters long. They are external feeders, attacking both whole grain and processes grain products. They love pet food, spices and tobacco. The mature larvae are whitish, C-shaped about 2.5-millimeters long and can be seen in infested product. Larvae pupate within the infested product in silken cocoons made out of food particles, an obvious sign of infestation. These brown beetles can also chew through packaging, making them even more pestering to deal with.

Flour Beetles are scavengers and prefer damaged or processed grains such as cracked grains, baking mixes and flour. The most common are the red and confused flour beetles. Their small size and flat bodies allow them to invade packaging easily. Major sign of infestation is seeing adults in infested product and storage areas.

Granary and Rice Weevils are easily identified by the distinctive snout projecting from the head of their reddish-brown bodies. They are internal feeders attacking only whole grains. The larvae which are C-shaped, develop within the grains, feeding from the inside hence making the grain hollow, which is one of the main signs of weevil infestation. When mature, the adults withdraw from the grains, leaving behind exit holes which are also characteristic of weevil-infested grains. (See image of rice weevil at the TOP of this article)

Spider Beetles resemble small spiders, and are scavengers feeding on a variety of both animal and plant product, especially products that are old, moist and moldy. They are common in older wooden building and damp structures. They are most active at night and in dark areas.

Relative size of the Sawtooth Grain Beetle.

Monitoring and early detection is key to controlling and managing stored product pests. Pheromones and lures are the best tools for this. If you suspect you have a pest issue, immediately contact your pest control provider so you can protect the product—and your reputation.

Alice Sinia, Ph.D. is the Resident Entomologist – Regulatory/Lab Services for Orkin Canada focusing on government regulations pertaining to the pest control industry. With more than 10 years of experience, she manages the Quality Assurance Laboratory for Orkin Canada and performs analytical entomology as well as provides technical support in pest/insect identification to branch offices and clients. For more information, contact Alice Sinia via e-mail at asinia@orkincanada.com or visit www.orkincanada.com.