Most of us have experienced a number of insect pests that are attracted to our food, whether at home or eating out, in pubs, restaurants or picnics. Insect pests such as flies, wasps and cockroaches are relatively easy to spot due to their size. There are, however, a number of insect pests much harder to notice as they are so small – especially at the egg and early larval stages – that you may need a magnifying glass to see them. Many of them spend a significant part of their life living inside their preferred food. These are collectively referred to as stored product insects (SPIs) or stored product pests.
These tiny pests cause a vast amount of economic damage in the food trade worldwide, from the farm through to storage, transport, processing, distribution and in homes and businesses. They consume, contaminate and spoil a significant proportion of the world’s food supply, especially in developing countries where poor food storage conditions enable insects to proliferate. Insect pests are estimated to destroy around 20% of the world’s grain crop production each year.
Stored product insects can enter the food supply chain at any point, from the field on a farm all the way to the consumer. They may be delivered with a food order, crawl or fly into a food storage area attracted by smells, and hide in cracks, crevices and hidden places around where food is stored. They are then ready and waiting to feed on the next batch of food brought in for storage.
There are three main categories of these pests:
Stored product insects can infest any dried and preserved foods and organic products, including grains, nuts, cereals, pasta, cheeses, preserved meats, wool and leather. They can be classified according to the plant and animal products that they infest.
The University of California Riverside and the UK Chartered Institute of Environmental Health classified insects into groups with similar habits in the way they infest stored products. Here are the categories and some of the most important pests — some feed on multiple food types and so appear in more than one category.
These are some of the most economically important pests of food globally, being able to destroy large amounts of grain in storage. Some such as the Khapra beetle is regarded an invasive species worldwide and subject to quarantine in countries such as the US and Australia:
This group of stored product insects feed on broken grains, flour, cereals and a wide range of other dried plant and processed products. They include some of the most important pests in grocery stores and homes. As there will always be some broken grains in any grain store, they can also be present in unprocessed whole grain stores and containers.
Dermestes beetles are generally carrion feeders and are pests of preserved and processed meats and cheese. They can breed in carpets, hides, bird and insect nests and dead rodents — they are even used to clean animal skeletons in museums. Larvae can bore into wood or other hard materials to pupate.
These species have been found in a wide range of foods in addition to those indicated by their names, including cereals, flour, nuts, seeds, chocolate, spices, beans, tobacco, dried fruit.
These stored product insects are generally feeders of multiple food types. They are more likely to infest dried fruit if it has been stored for long periods or if it is fermenting or decaying through poor storage. Some beetles feed on mould growing on rotting foods.
Bruchid beetles, such as the Bean Weevil, Acanthoscelides obtectus. This was originally a tropical species, from Central America, but has spread around the world in food shipments and is a significant pest in many countries.
Mites are widely distributed in the environment worldwide, occurring in a wide range of habitats, from soil, plant litter, under bark, as parasites of plants, birds, mammals and insects, and in nests of birds, rodents and bees. They are arachnids, not insects, which makes them more closely related to spiders, ticks and scorpions. They are the smallest of the pests when adult, at under 1 mm in length.
Several species are major pests of flour, grain, seeds, nuts, cheese and preserved meats. Some also feed on the fungi that develop on foods when they are stored in damp conditions and others are parasites of some of the beetle pests listed earlier. At least two species are also deliberately cultured on some cheeses to give a distinctive flavour.
Mites produce allergens that can affect people handling infested grain and flour and also dust and infested furnishings in the home.
It is important to conduct detailed inspections of stored products and storage areas to identify an infestation as early as possible. Examine deliveries on arrival and make regular checks on food that has been in storage for a while — make sure suppliers and shipping or transport agents also have a regime of inspection and monitoring.
The common signs of a stored product insect infestation are:
Our range of digital pest management solutions provide food businesses with new levels of efficiency and control