Top pests in food retail

The Food Retail sector faces threats from pests from multiple sources.

Large stores can stock tens of thousands of products from multiple sources with complex supply chains, requiring efficient monitoring and control procedures for supplies brought onto the premises.

Food handling activities range from raw meat and fish preparation, fresh dairy products, freshly cooked foods and bakery products, fresh fruit and vegetables, in addition to packaged goods.

It is important for businesses of all sizes to maintain sanitation standards and actively prevent pest infestation.

The presence of pests can cause enormous economic loss to the business owner, staff and suppliers.

The potential consequences of failure to maintain standards for the Food Retail sector include:

• damage to reputation and customer trust;
• lost sales and profits due to loss of customers;
• financial loss from cost of replacing damaged products;
• financial loss from claims for compensation;
• prosecution by public health and regulatory authorities;
• financial loss from fines from authorities;
• closure of the business by regulatory authorities or public health authorities.

The major pests affecting the Food Retail sector include rodents, flies, cockroaches, stored product insects, birds, ants.

Rodents

Rats and mice are attracted by food supplies but do not venture far from their shelter or nesting sites, so will nest close to food sources.

They are capable of a rapid increase in population given an abundant food supply, shelter from predators and benign environmental conditions inside a building.

The threats from rats and mice include:

• damage to buildings and fixtures: damage to electrical equipment is one of the most common problems and the brown rat can damage sewer systems;
• damage to machinery;
• contamination along access routes with urine, droppings, and filth picked up from the environment;
• damage to food containers and packaging;
• eating food in storage and on display;
• contamination of food with droppings, urine, filth;
• transmission 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: squeeks, 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 safety.

Technology developed by Rentokil for use in zero tolerance environments such as grocery stores and supermarkets can capture mice, eliminate them humanely without toxic chemicals, isolate them hygienically and wirelessly communicate with a secure online system to record the capture. The RADAR mouse capture unit and the PestConnect remote monitoring system enable 24/7 remote monitoring of a mouse infestation by the customer and Rentokil’s technicians.

Use of rodenticides

Rodenticides used 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 of 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.

These include 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 compliance.

Cockroaches

Cockroaches can cause particular problems in businesses that handle food because of their ability to hide in small places, their varied diet, rapid reproduction and the diseases they can carry.

Common species found in food handling premises globally

• German Cockroach (Blatella germanica): the adult is about 12-15mm long and light brown. It is one of the most common cockroaches worldwide and is easily identifiable by two dark stripes on the pronotum (head shield). It prefers warm, humid conditions but can infest food production areas and equipment, food storage areas, vehicles, offices and administrative areas, kitchens and bathrooms. They are good climbers and can climb vertical glass and tiled surfaces, so can spread quickly.
• American cockroach (Periplaneta americana): the largest cockroach that may infest facilities; adults are 35-50mm 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 20-30mm long 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. They are poor climbers on smooth surfaces but are cold tolerant (eg in the UK climate) and can be found outside buildings in drains, sewers, and external brickwork.
• Brown-banded cockroach (Supella longipalpa): the adult is only 10-15mm long and looks similar to the more common German cockroach. It needs hot humid conditions, around 27°C, to survive and outside warm climates will infest heated buildings and appliances such as light switches and electrical appliances.
• Australian cockroach (Periplaneta australasiae): a large species similar to the American cockroach. Adults are 25-35mm long with a reddish brown body and paler band around the pronotum (head shield); it is common in tropical climates (probably native to Africa, not Australia) but can survive in colder countries in warm, humid buildings such as greenhouses.

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

They can shelter in shelving in food stores, dark places such as cracks and crevices in walls and floors, drains, sewers, inside equipment and machinery and hidden spaces that provide the right temperature and humidity.

These places are also hard to reach using normal cleaning and sanitation methods.

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, storage and display areas on their bodies or in 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. Residual allergens remaining after cockroach control treatment will require cleaning to remove.

Cockroach prevention

Good sanitation practices 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;
• In food production areas, store food in cockroach-proof containers: they eat cardboard and paper so this should not be used for storage;
• A good inspection regime for equipment, buildings, incoming goods, stored and displayed products will pick up infestations and identify risks quickly.
• 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.

Cockroach control

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

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

Stored product insects

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

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

Most dried food products are susceptible to pests.

These include 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.

SPIs can also enter packaging made of paper, cardboard, plastic, cellophane and foil.

The entrance holes of some insects are smaller than can be seen by the human eye. For example, the larva of the Indian meal moth, therefore packaging without visible damage may harbour insect pests inside.

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.

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:

Moths

• 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.

Mites

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

Birds

Buildings provide safe areas for birds to roost around the structure and in spaces such as under roofs. Food stores and waste storage areas may also provide a food supply that attracts the birds.

Wild birds and their nests are protected by legislation and only birds regarded as pests can be controlled. The most common bird pests are pigeons, house sparrows, several gull species and starlings.

Bird damage

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 where there are deliveries and staff and the public walk, park vehicles and enter the premises.

Inside buildings, bird droppings, nesting material and feathers can contaminate surfaces, food products on display and in food preparation areas, equipment.

Apart from being unsightly, bird droppings 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

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 and delivery 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 repellent systems include:

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

Ants

Ants are more of a nuisance pest than a food safety issue in grocery stores.

They can find their way to food sources in buildings through the smallest gaps. They may infest fresh foods, food preparation areas, shelving, packaged foods — damaging both the packaging and the food inside — and in waste storage areas.

nts are not vectors of diseases but can pick up disease-causing organisms by mechanical contamination when walking on contaminated substances or surfaces.

There are over 12,000 known species of ant occupying a very diverse range of habitats.

They are generally opportunistic feeders and will forage for any food source available. Some preferring sweet foods and others protein sources or fresh leaves that are used to cultivate a fungus for food in the nest.

Common ant species in food businesses worldwide:

Pharoah ant (Monomorium pharaonis)

The Pharoah ant is one of the smallest ants, about 2mm long.

It originates in tropical areas but has spread around the world, infesting buildings and surviving in colder countries in heated buildings.

• A mature colony contains several queens which can set up new colonies with a group of workers and retain connection with the original colony — a process called budding.

• This allows them to quickly adapt to the conditions and move to colonies with more favourable situations.

• They can nest in tiny spaces, such as cracks in wood and concrete and even between sheets of paper, making extermination difficult.

   

Argentine ant (Linepithema humile, formerly Iridomyrmex humilis)

The Argentine ant is 1.6-2.8 mm long. It has spread worldwide from its native range in lowland Argentina to other South American countries, extensive areas of the Mediterranean, US, Australia, New Zealand, South Africa and Japan.

• It can feed on a variety of foods and displaces other ants out of the area, affecting local ecosystems.

• It is ranked as one of the world’s worst invasive animals.

• Pest control is difficult because of the numerous colonies and their ability to quickly adapt to colony loss and change in food supplies.

Businesses losses from ants

• Wasted food: food contaminated with ants must be discarded and disposed of;

• Reputational damage: the presence of ants in a store and in products bought by customers will cause adverse publicity and potential food safety notices or prosecution;

• Economic loss: the cost of wasted foods and their disposal, returned goods, lost business from reputational damage and the cost of food safety orders and prosecution.

Bibliography

WHO. Public Health Significance of Urban Pests. Copenhagen, WHO. 2008.

Keener, K. Safe food guidelines for small meat and poultry processors. A Pest Control Program. Purdue Expension, Purdue University.

Lupo L. Control of small flies. Quality Assurance Magazine. 31 March 2015.

Lupo L. Controlling Flies: Large and Small. Quality Assurance Magazine. 13 August, 2013.

Lupo L. Cockroach FAQs. Quality Assurance Magazine. June 3, 2014.

UNIDO. Good Manufacturing Practices: Pest Control. Paper 9.