Stored product insects are major pests in the food industry. Many species of beetle, weevil, moths and mites have evolved to feed on natural products such as seeds, grains, nuts, dried starchy products, wool and leather. We humans have learnt that these same products make nutritious food, either raw or as ingredients in a multitude of processed products, or they make useful items such as clothes and carpets.
Our activities in farming and handling food all along the food supply chain provide these stored product insects and arachnids with abundant food supplies and ideal sheltered breeding places — if we allow them access. Their size, from less than 1mm for mites and eggs and larvae of insects, to less than 1cm long for adult beetles and weevils, means that they can be difficult to detect until an infestation has a large population.
How do stored product insects harm food?
There may be no direct harm from eating the odd insect that has found its way into your food, and they generally only consume a small proportion of any stored food — if discovered early — but it is often the “collateral damage” that is the major problem. There are multiple ways that stored product insects can damage food.
Stored product insects damage stored food by:
Consuming the food product, resulting in loss of product
Causing physical damage to the product and degrading the quality, for example making holes in seeds, nuts and grain
Contaminating products with insect body parts, faeces, shed skins, pupae, webbing
Contaminating products with microorganisms: fungi, moulds, bacteria, viruses and parasites
Increasing the heat and moisture content through respiration of the pests and microorganisms, which in turn increases the growth rate of the pests and microorganisms
Contaminating products with mycotoxins produced by fungi they have introduced into the food
Changing the physical properties of ingredients, which can disrupt food processing machinery and spoil batches of product
Changing the smell and taste of the final product
Research commissioned by Rentokil showed that stored product insects cause the greatest financial losses to food processing businesses of all the pests that affect food businesses — including mice, rats, flies, cockroaches and birds. Out of 1000 companies surveyed in five countries, 60% said they lost 1-9 % of annual revenue to SPIs and 73% were concerned about losses due to SPIs.
The food processing businesses said they were affected by SPIs due to:
The aim of any food business is for complete exclusion of insects. Pest management programmes should focus on prevention, detection and early elimination of insect infestations using integrated pest management methods. Food processing facilities are often large, complex buildings with many opportunities for insects and other pests to enter. They will require pest management activities customised for the individual facility and location.
The key practices to prevent SPIs are:
Inspect all materials entering a facility, including raw materials and packaging that could harbour insects
Design the site, exterior and interior of the facility to minimise pests
Keep doors and windows shut and fit fine mesh screens
Securing buildings from stored product insect pests starts with the exterior. Food plant sites must be located and designed to prevent pests from accessing the plant, being attracted to it and finding conditions favourable for sheltering or breeding on the site. These are the main features to consider in choosing where the where the facility is located:
Surrounding areas: choose a site that is not at risk of insect infestations. Adjoining land and properties may be sources of insects that make the area a risk for food handling and processing and unsuitable for locating a facility.
Stagnant water: puddles, ditches, low areas and places with poor drainage can accumulate water that attracts insects to breed. This includes open concreted spaces such as vehicle parking areas. Organic material such as timber pallets standing in stagnant water will rot and become mouldy, attracting some SPIs that feed on mould.
Food waste storage area: food waste and other organic waste are prime attractions for many kinds of insects — which will follow the smell of food. Waste should be stored away from entrances, and in suitable containers with tight fitting lids. The storage area should be easily accessible and easy to manage. Waste should be removed regularly and the containers and surrounding area cleaned regularly to remove any solid or liquid food residues.
Vegetation: plants provide harbourage and food for insects and the smell of flowers, fruit, nuts and seeds attract insects. Keep areas around buildings free of vegetation as much as possible.
Lighting: lighting attracts insects so should be kept away from entrances to buildings where possible, or use lamps with low UV content — the main wavelengths that attract them. Suitably placed lighting could also be used to attract insects away from buildings. Inside buildings, UV light is used to attract insects that have got past all the precautions. Rentokil researchers have found that stored product insects are highly attracted to the UV light produced by our new Lumnia range of LED electric fly killers. One of our field biologists had an amazing result after installing them on a customer premises recently (summer 2018) — see below.
Building design and maintenance
Large, complex buildings can provide many places and features that are favourable for stored product insects to hide or gain access to the inside if details are not designed to specifically prevent them.
Openings: Buildings should have minimum openings such as windows, doors and vents.
Windows, doors and vents: should have fine mesh screens to prevent access to flying insects, and windows and doors must be kept shut when not in use.
Cables and pipes: they provide potential access routes for insects and should be sealed at entry points into buildings. Poor maintenance can allow more crawling and flying routes into a building to develop.
External doors: they should not open directly into areas processing food to maintain hygiene and prevent insects having a direct route into the area.
Roof drainage: roofs should have adequate drainage with no water accumulation and have no potential entry points into the building for insects or other pests.
Debris on roofs: roofs should be kept free of debris, which can provide shelter and food for insects, and bird nests, which support colonies of SPIs and can block drainage systems..
Heating, ventilation and air conditioning systems: these can leak or drip water, providing insects and other pests with a supply of moisture, or breeding sites if it is allowed to accumulate. They can also provide flying and crawling access points into the building if not designed or maintained properly.
Food loading and unloading areas: these should be designed and maintained to prevent stored product insects. The areas should be kept free of food and other debris and cleaned regularly.
Internal building design
The basic principle is to prevent the supply of food, water and shelter for insects, which requires a combination of design, maintenance and standard good practices for food hygiene.
Space for easy cleaning: The internal design of buildings and the layout of equipment and machinery should enable easy cleaning and maintenance to prevent build-up of food residues.
Materials used: floors, walls and doors should be made of materials that is durable, easy to clean and prevents cracks and crevices forming that can accumulate food residues and moisture and provide shelter for small insects. Regular inspection and maintenance is essential to keep them in a suitable state.
Openings for pipes and cables: should be sealed to prevent access for pests and prevent build-up of air-borne food residues in hidden, hard-to-clean spaces. Conduits can provide large amounts of space suitable for crawling insects to shelter and also routes to travel around the building.
Ceilings and roof spaces: need easy access for regular inspection and cleaning to prevent accumulation of debris and infestation by insects and other pests. They are are ideal places for debris to build up and insects and also rodents to shelter.
Drains: should be easy to maintain and clean. They require regular cleaning and maintenance to prevent build-up of organic matter and biofilms which can provide feeding and breeding sites for insects.
Electrical machinery: provides voids and crevices that are ideal for debris to accumulate and small insects to hide and breed. Electrical equipment also provides warmth that can improve breeding conditions. The siting of equipment can affect ease of cleaning and created difficult to get at places where insects could remain undisturbed and food residues accumulate.
Capture insects in the building
One of the last lines of defence in a food facility is to eliminate insects that get into the building without contaminating any food products. Electric fly killers are an efficient way to attract and safely contain any flying insects. Rentokil’s Lumnia Ultimate electric fly killer is designed for larger facilities such as food processors and warehouses. It has specially designed UV LED bulbs that are highly attractive to insects, which are captured inside the unit using glueboards and safely contained there.
When a customer came to us to solve a persistent problem with biscuit beetles (also called drugstore beetle, Stegobium paniceum) our local field biologist installed two Lumnia Ultimates. After only five days the units had captured an astonishing number of the beetles, as shown in the photo below of the glueboards inside one of the units on the site. This shows that the beetles are highly attracted to the LED UV bulbs.
Food hygiene regulations in all developed countries require food businesses to have adequate measures to maintain food hygiene and prevent contamination. These procedures should be based on Hazard Analysis and Critical Control Point (HACCP) principles — HARPC in the US regulations. Pest control is a component of Good Manufacturing Practices, which are prerequisites for carrying out HACCP procedures.