Insect pests

About 30 species of insect commonly infest food aid grain and grain products. Most insect pests are either beetles or moths, although there are some other types. In addition to insects, the only other invertebrates that are commonly found in stored food are mites. These are difficult to see as they are often less than 0.5 mm long; unlike insects they have eight legs and lack both wings and antennae.

• When these pests feed on grain, they produce heat and moisture and contaminate the food with their waste products and secretions.
• The various types of damage caused by insects and mites can lead to a weight loss of food, downgrading due to loss of quality, or even rejection of the commodity by the customer, all of which result in financial losses.
• The increase in moisture associated with pest infestation encourages the growth of moulds. Most moulds give the commodity an off-taste and colour, but some, such as Aspergillus flavus, may produce mycotoxins that can cause cancer in people and animals.
• Waste products from the pests, such as faeces, cast skins and chemical secretions, are sometimes harmful and often give the food an unacceptable flavour and colour. An allergic reaction can occur in some people when eating or handling such contaminated commodities.

As well as attacking the commodity, several insect pests create other types of damage. Some species that bore into grain may also burrow into wooden or plastic structures, weakening them. The larvae of many moths produce large quantities of silken threads when moving over surfaces. This builds up into webbing that can bind flour and grain together into a solid mass, blocking machinery or causing additional machine wear and breakdowns.