Food Processing

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Pests in Food Processing

Pest control is an essential part of Good Manufacturing Practice in food processing from a hygiene, economic and regulatory viewpoint.

Pests can carry a wide range of diseases causing organisms, including bacteria, viruses, protozoa and helminths that can cause harm to consumers and staff of businesses processing and handling food. They can also cause physical contamination of ingredients and processed products from, for example, droppings, shed fur and feathers, body parts, nesting material and damaged packaging.

Pests and Legislation

Legislation requires pests to be excluded from food processing plants and the prevention of food contamination by pests. Effective measures need to be taken to maintain hygiene and keep adequate documentation. This includes applying current good manufacturing practices and the use of systems such as HACCP to:

  • identify points at each stage in the operations that are critical to the safety of food, including in the supply chain;
  • implement effective control procedures;
  • monitor control procedures to ensure their continuing effectiveness; and
  • review control procedures periodically, and when changes are made to operations.

Financial threat

Not taking adequate measures to prevent and control pests can lead to substantial financial costs to the business from stock and product loss, product recall, loss of reputation and legal action that could ultimately cause the closure of the business.

Threat from the supply chain

Pests can be brought into the food processing facility through the supply chain, in the ingredients or packaging, and the facility itself will attract pests through food odours and lighting. The buildings provide shelter, warmth, food, water and safety from predators, which are ideal conditions for proliferation unless appropriate action is taken.

The role of Integrated Pest Management

Control of pests in food processing requires the implementation of an Integrated Pest Management program. This has three basic steps: inspection, identification and treatment but is a complex process that requires specialist expertise to implement to achieve accredited food standards and comply with legislation.

Top Pest Concerns for Food Processors

The range of pests found in food processing plants will vary according to climate, geography and food ingredients processed, but the most common ones are beetles, moths, rodents, cockroaches, and flies.

Stored product insects

Stored product insects (SPIs) is a generic term that covers beetles, weevils, moths and mites (which are actually arachnids) infesting food in storage anywhere in the food chain from the farm to the kitchen.

A Rentokil commissioned survey of 1,000 companies in five countries found that they were the pest category that caused the most economic losses to food processing companies:

  • 60% reported annual revenue losses of 1-9%;
  • 73% reported feeling highly or moderately concerned about income loss

In food

Stored product pests are most likely to be in a food ingredient on delivery to a processing factory or a processed food product when stored for a long time.

  • Most dried food products are susceptible to pests, including cereal products, seeds, nuts, dried fruit, spices, powdered milk, tea and preserved meats.
  • All stages of the pest can be present simultaneously, eg egg, larva, pupa, adult.

In packaging

They can also enter packaging made of paper, cardboard, plastic, cellophane and foil. The entrance holes of some insect are smaller than can be seen by the human eye, so there may be no visible damage to packaging containing pests.

Insects and mites may only consume a small quantity of food but can contaminate large quantities through physical damage, faeces, cocoons, etc and the introduction of microorganisms that cause further degradation, making food unfit or unacceptable for human consumption.

The pest activity in raw product ingredients can also change their physical and chemical properties, causing them to cake during processing which can halt production lines and damage machinery.

The cost of stored product insects

The Rentokil research found high percentages of companies affected by direct costs and delays caused by SPIs:

  • raw material contamination leading to replacement cost (37%);
  • raw ingredient contamination leading to replacement cost (45%);
  • finished goods damage leading to replacement costs (38%);
  • product delays and additional treatment (30%);
  • fines or closure (10%).

Signs of stored product pests include:

  • damage to stored products, such as small holes in nuts or grain;
  • live or dead insects (small beetles and moths), larvae, pupae or silken webbing on food storage bins;
  • infestation, holes, larvae or webbing on the outside of packets or bags;
  • larvae, pupae or silken webbing in food harbourages in cracks and crevices around shelves or on machinery;
  • larvae, pupae or silken webbing in food spillages;
  • larvae, pupae or silken webbing on beams and window sills;
  • pests caught in insects traps.

Common stored product pests and the foods they infest are:


  • Indian meal moth: nuts, dried fruit and grain.
  • Mill moth: flour.
  • Tropical warehouse moth: stored cereal, nuts, dried fruit, oil seeds and oil cakes.
  • Warehouse moth: cocoa beans, chocolate confectionery, dried fruit and nuts.

Beetles & weevils

  • There is a very large number of species of beetle and weevil that feed on dried foods such as: cereals/grains, flour, seeds, nuts, pulses, dried fruit, chocolate, spices and processed products including pasta.


  • Cheese mite: cheese, nuts, dried eggs, fruit, flour, tobacco.
  • Flour or grain mites: cereals, dried vegetable materials, cheese, corn and dried fruits.

Stored product pest control

These pests are controlled by using standard quality control measures throughout the supply chain, for managing suppliers, logistics companies, incoming shipments, storage of raw materials, processing, packaging and storage of final product.


The ship rat, which used to be more common, is generally confined to some port areas.

Rats and mice are attracted by food supplies and do not venture far from their shelter or nesting sites, so in a large facility will nest close to accessible food stores.

Rats and mice are capable of a rapid increase in population given an abundant food supply, due to the number of litters they are capable of producing and the time to maturity, shelter from predators and benign environmental conditions inside a building.

Hazards to food processing

The hazards to food processing facilities from rats and mice include:

  • damage to buildings and fixtures; the brown rat can also cause extensive damage to sewer systems. Rats are the most destructive pest, according to the Rentokil survey, with damage to electrical equipment the most common problem;
  • damage to machinery leading to production downtime — 20% of companies surveyed had suffered from this;
  • contamination along access routes with urine, droppings, and filth picked up from the environment;
  • damage to food containers and packaging;
  • eating the food in stores and packages;
  • contamination of food with droppings, urine, filth;
  • transmission of a large number of diseases, including Salmonellosis, Leptospirosis, Toxoplasmosis, Lyme disease, rat-bite fever;
  • rodents carry ectoparasites, including ticks, fleas, lice and mites and are therefore also vectors for the diseases that these carry;
  • rodents are reservoirs for some mosquito-borne diseases.

Signs of rodents

Rats and mice have distinct but different signatures that show which pest is present:

  • droppings, which have a distinctive size and shape for each species;
  • sightings of live or dead animals;
  • noises: squeaks, gnawing sounds, scurrying sounds;
  • smudge marks along runs caused by their oily fur;
  • tracks in dust or powder used for the purpose;
  • gnawing of building materials, wiring, food and packaging: the gnaw marks are distinctive;
  • urine stains are left by both rats and mice and can be detected using UV light;
  • urine pillars form where mice infest an area over a long period — and would show a serious failure in pest control.

Rodent control

Control of rodents involves the elimination of harbourage in and around buildings and preventing access to food, water and shelter. There may be many points of entry to a building, such as cracks, vents, pipes, cabling, drains, doorways, windows, screens, where measures can be taken to prevent access. Any rodents present must be controlled using traps or poison according to acceptable practices and legislation related to food processing.

Use of rodenticides

Rodenticides used in food processing facilities must be approved products, placed in secure bait stations and restricted to areas where food is not processed.

If stored on site they must also be stored in suitable conditions that prevent contamination from the poison in food products and the environment.

Expertise is needed to determine the type of bait used, where it should be placed and the frequency, the monitoring regime and the documentation, which is best done using an outside contractor. If done in-house, staff will need to be certified to handle the chemicals and carry out the rodent control activities.

There are specific requirements for documentation in food standards and legislation, such as maintaining maps of all bait stations, records of sightings, records of training of staff, the monitoring regime, therefore it is important to have trained personnel responsible for this.


They cause particular problems for food processing because of their size (giving them the ability to hide in small places), their varied diet, rapid reproduction and the diseases they can carry.

Common cockroaches

There are over 3,000 species of cockroach, but just three species are commonly found in food processing plants:

  • German Cockroach (Blatella germanica): the adult is about 12-15mm long and light brown. It prefers wet, humid conditions and can infest production areas and equipment, food storage areas, vehicles, offices and administrative areas, kitchens and bathrooms.

  • American cockroach (Periplaneta americana): the largest cockroach that may infest facilities, adults are 35-40mm long and reddish brown. It requires warm, humid environments to survive. They are found in drains, sewers, basements, storage rooms and waste storage areas.

  • Oriental cockroach (Blatta orientalis): the adult is 20-25mm long, intermediate between the other two and has a dark brown or black body. It prefers cooler, dark and damp places to shelter, such as basements and drains, and can be found in storage rooms and waste storage areas.

Cockroaches are primarily nocturnal, sheltering in the daytime and coming out at night to find food and other sites for shelter.

The challenge with cockroaches is that they shelter in places, which are hard to reach using normal cleaning and sanitation methods.

They like dark places such as cracks, crevices, drains, sewers, inside equipment and machinery and hidden spaces that provide the right temperature and humidity.

Risks from cockroaches

  • Diseases and allergens: cockroaches can carry a large number of disease-causing bacteria, including Salmonella, Staphylococcus, Listeria, E. coli, and also fungi, viruses and parasitic worms;
  • they feed on decaying matter, mould, faecal matter in sewers, from rodents and birds, and animal carcasses, which can then be transmitted into the food production environment on their bodies or from excreta;
  • they defecate along their pathways;
  • they frequently expel saliva on surfaces to ‘taste’ their environment;
  • droppings and bodily secretions stain and leave a foul odour that can permeate infestation areas, food and packaging;
  • cast skins and egg cases contaminate products and packaging;
  • droppings and shed skins contain allergens, and heavy cockroach populations can trigger asthma attacks.

Cockroach prevention

Good sanitation practices in the food facility will help prevent infestations and pick up the presence of cockroaches:

  • Cockroaches can feed on small residues of food left from spills or in preparation areas, so good cleaning practices which eliminate the residues quickly will deny them a food supply;

  • Store food in cockroach-proof containers: they eat cardboard so this should not be used for storage;

  • Maintain drains in good condition to prevent accumulation of food debris and means of access and shelter;

  • Removal of waste from food production areas, garbage container design that denies access to all pests, positioning of garbage containers away from the food storage and processing areas, emptying and cleaning frequently, all reduce risk of infestation;

  • Good building design can reduce the risk of access eg through spaces around pipe and cable ways, vents, screens, windows, doorways, sewers; and harbourage in small spaces such as junction boxes.

  • A good inspection regime for equipment, buildings and shipments will pick up infestations and identify risks quickly.

Cockroach control

A number of treatments are available for control of cockroaches, including sprays, aerosols, dusts and bait. In a food processing facility the insecticides used must be permitted for use by the relevant authority and will require competent, trained personnel to apply them.

Rentokil uses chemical-free control methods suitable for sensitive business environments and Insect Monitor Units to detect signs of activity.


The impact of a fly infestation on a business is not just a loss of income.

A number of fly species are attracted to the odours present around food processing plants, including fruit flies, drain flies and filth flies, including house flies.

  • For pest control it is important to identify which species is present as each has different attractants and breeding habits.

Different fly species are attracted to different food products, including fermenting sugars, oils and fats, carbohydrates, and decaying proteins and vegetable matter.

Fruit flies

Fruit flies are attracted to fermenting sugary liquids, in which they can feed and breed in very small amounts. The liquid can accumulate in:

  • garbage containers;
  • over-ripe fruit, and some vegetables;
  • old drink bottles;
  • in drains;
  • in spills;
  • in cracks in wet floors.

Drain flies

Drain flies are attracted to rotting food, sewage and other organic waste material. They lay eggs in organic waste that can build up in drains or polluted shallow water.

They can breed in the gelatinous bacterial films — biofilms — that form on surfaces in drains, septic tanks, compost, etc, and are resistant to cleaning and pest-control chemicals.

Their ideal environment can be prevalent in food processing facilities where food particles are washed into the drains during regular cleaning activities.

Risk from flies

In warm conditions with suitable ‘substrate’ to breed in flies have a short lifecycle and can multiply rapidly.

Food processing facilities can provide an attractive array of suitable substrates for flies, if hygienic practices are not adequate.

Carriers of over 100 pathogens

Filth flies, including house flies, drain flies and flesh flies are known to be able to carry over 100 pathogens that can cause disease in humans, including Salmonella, cholera, Shigella, Campylobacter, E. coli, Cryptosporidium, parasitic worms and fungi.

  • They feed on faecal matter, garbage, rotting materials as well as stored and processed foods in food processing plants.

  • They will regularly move between the contaminated food sources and clean areas, carrying contaminated filth on their bodies as well as microorganisms internally.

  • Many types of fly have hair like structures on their bodies, hairs and sticky pads on their feet and deeply channelled mouth parts that can pick up contaminated material as they feed.

  • Also flies such as house flies regurgitate digestive juices and defecate while feeding and resting, contaminating foods and surfaces with microorganisms that can cause disease or decay.

  • Fruit flies are not generally considered to be as great a health risk as other flies because they are not thought of as filth feeders. However, they do need a protein supply to produce eggs and this can be animal faeces.

Several studies have found that fruit flies can transmit faecal material to fruit, where they lay their eggs by puncturing the skin, and can transmit E. coli. Therefore fruit flies need to be regarded both as potential vectors of spoilage microorganisms and disease.

Controlling flies

The application of standard hygiene practices are particularly important for controlling flies to reduce the attractive odours, feeding material and breeding sites.

These include:

  • supplies are not brought in or stored in a rotting state;
  • production areas and equipment are cleaned and inspected regularly, including in cracks, crevices and hidden spaces where even traces of food and liquid can accumulate;
  • garbage is disposed of regularly — at least twice a week in hotter climates;
  • garbage containers are cleaned, not overflowing and can shut properly;
  • all equipment used to handle garbage is cleaned regularly;
  • there is sufficient storage volume for the waste produced;
  • the areas where garbage is stored are kept clean and well maintained;
  • supply areas and vehicles where spills can accumulate and decay are kept clean;
  • the same hygienic practices are applied to canteen and kitchen areas;
  • drains are kept free of accumulating organic matter and cleaned with cleaner for biofilms; microbial drain cleaners are also available to digest organic matter so it can be washed away.

Exclusion is dependent on the design and maintenance of the facility, including:

  • use of screens on windows and vents, maintained in good condition;
  • appropriate door design for the purpose eg automatic doors, air curtains, roll-up doors; vinyl strip doors;
  • doors are kept shut when not in use;
  • the building is maintained to prevent gaps appearing in any part of the building fabric that would allow insects to enter;
  • UV light traps and pheromone traps can be used to trap flies to help prevent build-up of breeding populations.


As a last resort pesticide is applied using approved products applied by trained personnel following accepted practice.


The most common bird pests are pigeons, house sparrows, seagulls and starlings.

Birds can cause physical damage by dislodging roof tiles, particularly the larger birds, and blocking guttering with nests and feathers.

They produce substantial amounts of droppings which foul buildings, vehicles, paved areas and building entrances.

Inside buildings, bird droppings, nesting material and feathers can contaminate surfaces, machinery and food products.

Apart from being unsightly, birds can transmit many human pathogens including viruses, bacteria, fungi and protozoa. More common microorganisms include Salmonella, E coli and Campylobacter.

Bird nesting and roosting sites also encourage infestations, of arthropods such as bird mites, fleas and some beetle species.

Bird control consists of preventing access to food, water and shelter. Basic practices to prevent access to food and water are:

  • keep doors closed when not in use;
  • remove spillages quickly;
  • keep garbage storage areas clean and containers shut;
  • garbage containers should be bird proof;
  • remove any standing water where possible;
  • regularly check food storage areas for potential bird access points.

Denying shelter includes eliminating nesting and feeding sites on buildings and in the vicinity of the facility. This should start with the design of the facility and include measures to prevent access to flat roofs, balconies, ledges, chimney stacks, guttering and culverts, which are favourite areas for nesting.

Bird repellant systems include:

  • netting;
  • needle strips;
  • electric bird deterrent;
  • scaring devices;
  • traps;
  • entry barriers eg vertical plastic strips, automatic doors;
  • sticky pastes.