These pests are becoming a major threat to the dried and processed food stuff worldwide. The larvae of food moths feed on dry fruits, cereals, chocolate, nuts, legumes and the result is a substantial economic loss to the stored food products. Adult moths are seen in grain storage, warehouse, flour mills and dried food processing or manufacturing facilities.
The adult moths are 7-9mm long and have a wingspread of 20mm. The forewings are pale grey with the outer portion of the wing a reddish-brown to copper colour. Females begin to lay eggs on larval food materials. Each female can lay 200 to 400 eggs.
The egg hatch in 2 to 14 days and the larvae begin building the silk and frass tunnels in which they live and feed. Food products often become matted with their silken webbing. Larvae mature in 4 to 5 weeks and often wander away from the food source in search of pupation sites. The pupal period is about 2 weeks. The entire life cycle can be completed in 6 to 8 weeks under favorable conditions.
Larvae cause damag by spinning silken threads with food particles as they feed and crawl thus webbing food particles together. Some food becomes matted with silken webbing. In stored grains, feeding is done at the surface and on the seed germ. Indian meal moth larval feeding reduces the dry weight of grain thus reduced commercial value. Severe infestation could lead to a mould problem in grain.
Adult mating takes place immediately after the adults emerge. Adults females lay eggs in groups and singly, up to 350 eggs are laid and these may be stuck to various foods by a sticky secretion. Adult stage completed with 10-14 days. The eggs hatch in 4-28 days to give white or pinkish larvae and spin silken tubes in which they live. After 3-5 moults the larvae are full grown and 15-19mm long. They then wander away from food and pupate for 7-16 days in the dark corners of buildings or machinery. In colder climates these moths overwinter as larvae but, in contrast to other species, usually remain in the foodstuff.
The newly emerged larvae move to the stored products. Young larvae feed voraciously and make web or silk. Mill moth larvae prefer wheat flour, but will also feed on all sorts of grains, cereals, seeds, dried fruits, nuts and almonds. Larvae produce unpleasant smell in the infected product and leave faeces in the product as well. Larval webbing can cause serious blockages in provender mills. The larvae eat holes in sifting silks and may also reach the mill’s finished products.