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Pest Control in Food Establishments

Course Introduction

Welcome to the Pest Control in Food Establishments Course

Controlling pests in a food processing or storage facility is essential in order to minimize the transmission of food-borne illnesses caused by contamination.

Pests common to food establishments are divided into three categories.

This course will provide an overview of the different categories of pests as well as indicators of pest infestations. Knowing what to look for and the potential dangers posed by these pests can help make food establishments safer for everyone.


Course Overview

After completing this course, you should be able to identify signs of pest presence and describe measures to control pests in food establishments.


Course Structure

The remainder of the course is divided into the following four lessons:


Introduction to Food Pests

Lesson Overview

This lesson describes the significance of food pests and explains why they are a concern.

After completing this lesson, you should be able to:


Significant Pests in the Food Industry

The food industry is concerned with filth from pests—including insects, rodents, birds, and bats—that may adulterate or contaminate human food.

These pests are considered significant in the food industry because:

Filth is any contaminant that, because of its repulsiveness, would not normally be eaten. Filth may or may not be an actual health hazard; its mere presence in a product will render that product adulterated.


Pest Attributes

Five key attributes are used to describe pests:


Classification of Pests

There are three forensic categories of pests:

These categories are tied to the relative significance of the threat these pests represent and recommended regulatory actions in response to their presence.

Each category has a unique forensic profile that is used to place pests within the category.


Category I: Vectors

Category I pests are high priority and include pests that are potential vectors for food-borne pathogens. A vector is an organism that transmits a pathogen from a reservoir to a host. Pests that are known to carry pathogens are considered vectors regardless of whether a microbiological hazard is actually detected.

Pests in this category have the following attributes:

In other words, if a pest lives around people, enters buildings, is attracted to and moves back and forth between filth and human food, and is known to carry food-borne pathogens, it is a Category I pest.


Category I Examples

Examples of Category I pests are:


Category II: Indicators of Insanitation

This category includes pests whose presence in food or in the vicinity of food processing or storage areas is an indication of insanitary conditions.

These pests are considered medium-priority pests and are divided into four groups:

  1. Opportunistic pests: These pests are opportunistic in the sense that they come into places and steal food, but they don’t live or breed in the food. They carry it away or they come, eat, and then leave.

    Examples include the common silverfish, Argentine ant, and lesser bandicoot rat.
  2. Adventive pests: These pests are not found living in the actual food product. They’re more attracted to the building itself than to the food. Looking for shelter, they enter the building and may be found roosting, building a web, nesting, or hibernating.

    Examples include the cluster fly, cellar spider, pigeon, and little brown bat.
  3. Obligatory pests: These pests are the true storage insects. They normally live and breed in the food, so infested food will contain evidence of the entire life cycle—eggs, shed skins, larvae, pupae, and adults.

    Examples include the granary weevil, confused flour beetle, cigarette beetle, Indian meal moth, cheese skipper, and booklouse.
  4. Parasites and predators: These pests are attracted to a Category I or II host or prey, not to the food itself.

    Examples include the ensign wasp, warehouse pirate bug, window pane fly, and house pseudoscorpion.

Category II Attributes

All Category II pests exhibit synanthropy and endophily (association with humans or their dwellings and willingness to enter buildings).

The pest groups vary in other attributes as shown in the following table.

  Synanthropy Endophily Attraction to Stored Food Communicative Behavior
Opportunistic Pests Yes Yes Yes Yes
Adventive Pests Yes Yes No No
Obligatory Pests Yes Yes Yes No
Parasites and Predators Yes Yes Attraction to a host or prey in Category I or II


Category III: Incidental Pests

This category includes agricultural pests, nuisance pests, and other incidental pests that do not have the attributes of Category I or II pests. They are considered low-priority pests because they pose no health hazard and are not indicative of insanitation. However, their presence in food—while not a health hazard—would be aesthetically unpleasant and unacceptable.

Examples of incidental pests include:


Lesson Review

You have completed the Introduction to Food Pests lesson. You should now be able to:

The next lesson will discuss insect pests.


Insect Pests

Lesson Overview

This lesson describes the significance of insect food pests and explains why they are a concern.

After completing this lesson, you should be able to identify key characteristics of significant insect pests, including:


Insect Life Cycle

Insects go through many forms during their life cycle. It is helpful to be generally familiar with insect life cycles as insects in any of these stages may be observed in or near food products.

The development of an insect from egg to its adult form, called metamorphosis, takes different lengths of time in different insects.

After hatching from an egg, an insect must periodically shed its skin as it grows—a process known as molting. The intervals between molts are stages or stadia, and the form an insect takes during a particular stage is termed an instar. Insects vary widely in the number of instars they go through.


Insect Metamorphosis

There are two main types of metamorphosis in insects:

In simple metamorphosis, the immature stages are called nymphs and are similar to mature adults in appearance. Cockroaches and crickets undergo simple metamorphosis.

Simple metamorphosis, showing progression from egg to nymph and adult

In complex metamorphosis, the immature stages are called larvae and are different from the adult form. Larvae and adults often live in different habitats and have very different behavior. Larvae enter an inactive state called pupa, emerging as adults. Ants, beetles, flies, and moths all undergo complex metamorphosis.

Complex metamorphosis, showing progression from egg to larvae, pupa, and adult

Category I Insects: Cockroaches

Cockroaches are members of the family Blattidae. They range in size from 5/8-inch to 1-1/2 inches and are prolific breeders.

Disease-producing organisms (bacteria, protozoa, and viruses) have been found in and on cockroach bodies. Different forms of gastroenteritis (food poisoning, dysentery, diarrhea, etc.) appear to be the principal diseases transmitted by cockroaches. Cockroaches have been known to mechanically transmit Salmonella and cholera. Disease-causing organisms are carried on the legs and bodies of cockroaches and are deposited on food and utensils as the insects forage. They can also cause allergic reactions in some people.

Cockroaches are attracted to warm, moist, dark environments. They feed on organic material, including starches, sweets, grease, glue, and meat products. They tend to avoid light and forage at night. During the day they hide between and under equipment, under sinks, and in floor drains. Because these areas generally cannot be properly cleaned, the cockroaches come in contact with considerable filth and bacteria.

Signs of a cockroach infestation include:


Category I Insects: Flies

Some types of flies, including the blow fly, house fly, drain fly, and flesh fly, are a concern in food establishments as they feed on and lay eggs in sewage, garbage, manure, carrion (dead animals), and other filth sources, where they pick up pathogenic organisms. The organisms are deposited in food or on food preparation surfaces in the fly’s excreta (feces and vomit) and from hairs and bristles on the body. Flies can transmit Salmonella, E. coli, Vibrio, and Shigella.

Signs of a fly infestation include:


Category I Insects: Pharaoh Ants and Thief Ants

Pharaoh ants and thief ants form colonies inside buildings. Both types of ant feed on a wide variety of foods, including sweets, fats, proteins, and living and dead insects. Thief ants get their name from their habit of nesting near or in the nest of other ants, from which they steal food and larvae.

Pharaoh ants can carry numerous disease-causing bacteria, including Salmonella, Pseudomonas, Staphylococcus, Streptococcus, and Clostridium.

Thief ants have been found feeding on dead rats and mice and are potential carriers of disease-inducing organisms to human food. They may also serve as intermediate hosts for the poultry tapeworm.

Signs of an ant infestation include:


Category II Insects

This section of the lesson will provide information on insects that are indicators of insanitation. The following examples from the groups in this category will be included:


Category II Opportunistic Pests: Silverfish

Silverfish (Lespisma sacchrina) preferred foods include flour, dried meat, rolled oats, paper, and glue.

They are typically found in warm, humid environments and are more active at night.

Signs of silverfish infestation include:


Category II Opportunistic Pests: Argentine Ant

The Argentine ant (Linepithema humile) is a common opportunistic pest of households and food facilities. It will often enter structures in search of food or water (particularly during dry or hot weather), or to escape flooded nests during periods of heavy rainfall.

Argentine ants are difficult to control because they form large colonies with multiple queens, and the colonies are relatively mobile (they will quickly move their larvae and pupae when disturbed).

Foraging adult ants are only a fraction of the total colony and if killed are quickly replaced by others. These ants will form colonies in the ground, in cracks in concrete walls, and in spaces between boards and timbers.

Argentine ants feed on foods high in sugar (e.g., honey) and high in protein (e.g., insects).

Signs of an Argentine ant infestation include:


Category II Adventive Pests: Cluster Fly

Cluster flies are adventive pests, attracted to the building, not food. When the adults emerge in the late summer or autumn, they enter buildings to hibernate, often in large numbers. The cluster fly is in the blowfly family Calliphoridae. Cluster flies lay their eggs outdoors near earthworm burrows, and the larvae then infest the worms.

Cluster flies are primarily a nuisance pest and do not present a health hazard. Cluster flies can be found in the upper stories of buildings and in roof and wall cavities.

Signs of a cluster fly infestation include:


Category II Obligatory Pests: Storage Insects

Storage insects include:

These obligatory pests infest stored grains, where they live and breed.

Failure to inspect incoming food, keep storage areas clean, and rotate stock provides an inviting source of food and can lead to serious infestations. Because these insects live and breed in the food, the food product becomes adulterated with insect eggs, larvae, pupae, and adults, shed skins, and fecal material.


Category II Obligatory Pests: Dermestid Beetles

Most dermestid beetles are scavengers that feed on dry animal or plant material such as skin, animal hair, pollen, and plant fibers. They can be a serious pest in premises where animal products are processed as they breed on any animal protein.

Dermestid beetles cause significant damage to stored grains and other products. The Khapra beetle is considered to be the world’s most destructive pest of stored grain and grain products. Exposure to grain contaminated with dermestid beetle skins and hairs can lead to skin irritation and gastric health hazards such as ulcerative colitis.


Category II Obligatory Pests: Storage Insect Infestation

Signs of a storage insect infestation include:


Category II Parasites and Predators: Warehouse Pirate Bug

The warehouse pirate bug (Xylocoris flavipes) is a predatory insect that preys on other grain storage insects.

These insects are not injurious to stored grain because they don't get inside grain kernels, and they don't eat the grain. Instead, they eat the eggs, larvae, and pupae of many species of harmful grain insects.

Pirate bugs are easily removed from the grain before it is used. These bugs are widespread and common in grain storage, and commercially produced as a biological control agent.

Large naturally occurring populations of pirate bugs may indicate the presence of injurious storage insects, which in turn may indicate insanitation.


Category II Parasites and Predators: Parasitic Wasps

The lesser ensign wasp (Szepligetella sericea) is a wasp that lays its eggs inside cockroach egg cases. The wasp larvae feed on the cockroach egg.

The adult wasps feed on flower nectar, and do not bite or sting.

As these wasps are typically seen in areas with abundant cockroach populations, their presence in buildings indicates a cockroach infestation.


Lesson Review

You have completed the Insect Pests lesson. You should now be able to identify key characteristics of significant insect pests, including:

The next lesson will discuss mammal and bird pests.


Mammal and Bird Pests

Lesson Overview

This lesson describes the significance of mammal and bird pests and explains why they are a concern.

After completing this lesson, you should be able to identify key characteristics of significant mammal and bird pests, including:



This lesson will review the Category I pests:



Significant Category I rodent pests include:

Rodents such as these can carry disease, including leptospirosis, salmonellosis, shigellosis, and hanta virus, and can contaminate food products with urine, feces, and hair. Rodents pose an additional hazard to food establishments as they can cause extensive damage via gnawing and can cause fires by chewing electrical wiring.

Rodents prefer foods high in fat, protein, or sugar. They will feed on cereals, grains, seeds, fruit, insects, meat, and fish. Rats and mice will nest in a variety of locations, including wall cavities, areas under roofs, dry store rooms, trash can areas, box collection areas, and outdoor vegetation.

Signs of rodent infestation include:



Bats are flying mammals of the order Chiroptera. There are over a thousand species of bats. Bats have poor visual acuity but well-developed senses of smell and hearing. They hunt mostly at night and use echolocation (bouncing vocal sounds off surfaces) to navigate.

Most bats found in the United States eat insects. They enter buildings to roost, not because they are drawn by a particular food source. They are able to squeeze through narrow slits and cracks as small as a dime.

Bats in food establishments may contaminate food and food contact surfaces with feces and urine (guano), which they drop when roosting or when in flight. Guano can become breeding media for insects if not quickly removed. Bats can harbor numerous pathogens, including those causing rabies, severe acute respiratory syndrome (SARS), and histoplasmosis.

Signs of bat infestation include:                                           



Pigeons, sparrows, and starlings are responsible for the majority of bird problems at food establishments. Other problematic birds include swallows, crows, and seagulls.

Birds can pose a major threat in and around facilities where food is being prepared, processed, or stored because:

Birds can gain access to food preparation and storage areas through doors, windows, and ventilators.

Signs of a bird infestation include:


Lesson Review

You have completed the Mammal and Bird Pests lesson. You should now be able to identify key characteristics of significant mammal and bird pests, including:

The next lesson will discuss control measures for food establishments.


Control Measures

Lesson Overview

This lesson describes control measures that can be taken to reduce the occurrence of food pests.

After completing this lesson, you should be able to:



Controlling pests in a food processing facility is essential in order to minimize the transmission of food-borne illnesses caused by microbial contamination.

Effective pest control is based on:

Pest control requires vigilance inside and outside the plant. This includes:


Control Measures for Grounds

Controlling pests in a food processing facility begins on the grounds surrounding the facility.

The following practices can reduce infestation on the facility grounds:



Exclusion is the best way to control pests inside the food processing or storage facility.

The following practices can help prevent pests and their associated pathogens from entering the building:


Inside the Plant

Inside the plant itself, good sanitation can reduce the likelihood of infestation.

The following basic sanitation practices should be followed:

Using effective storage practices inside the plant can also reduce pest infestations, including:



For more information on control measures to reduce pests in food establishments, select the following links:


Lesson Review

You have completed the Control Measures lesson. You should now be able to: