The main categories of foods subject to insects and pest attack are fruits, vegetables, grains and their processed products. Warm humid environment promote insect growth, although most insects will not breed if the temperature exceeds above 35°C or falls below 10°C. Many insects cannot reproduce satisfactorily unless the moisture content of their food is greater than 11 per cent.
The presence of insects and pests and their excreta in foods may render consumable loss in the nutritional quality, production of off-flavours and acceleration of decay processes due to creation of higher temperatures and moisture levels and release of enzymes. The products of insect and pests activities such as webbing, clumped-together food particles and holes can also reduce the food values.
Rats and mice carry disease-producing microorganisms on their feet and/or in their feces and urine and contaminate the food by their presence.