Insect pests of stored grains are the descents of earlier insects which came into existence 250 to 500 million years ago. Insects that are associated with stored grain and grain products constitute beetles, weevils and moths. Several hundred species of insects are associated with stored grain and stored grain products but only 14 species are well adopted for living in stored grain and responsible for most of the damage. Minor pests constitute approximately 175 species of insects and mites that may rise to populations that are injurious to grain and grain products. The group of insects that damage stored grain can broadly be placed in two groups. The first group, internal feeders spend the most of their life, feeding within the kernel of grain and the second group, external feeders spend their life feeding on the surface of grain or on the finished products of grain.
Storage losses by insects in India
Nearly 70% of the grain, annually produced in the country is retained by the farmers for their own food, cattle feed, seed, etc. The farmers generally store their grain in traditional storage structures. The Government of India appointed a committee in 1966 headed by Dr.Panse, the then member of the planning commission to study post-harvest losses. The committee estimated the post-harvest losses to be around 9.3% of which losses during storage alone are estimated at 6.6% out of which insect alone causes around 2.5% loss.
Among biotic and abiotic factors which affects grains in storage, insects play a major role in the deterioration of food grains causing both quantitative and qualitative losses. Often the presence of the insects in store houses are felt only when they are hovering and flying around, by which time enormous loss and population build up of insects might have occurred.
It is well proved that no granaries can be filled with grains without insects as the harvested produce contain egg (or) larvae (or) pupae in them because of field carryover infestation which cannot be avoided in developing countries like India. So what is required is simple technologies for timely detection of insects in the stored produce and thereby plan timely control measures.
Many devices have been developed for stored grain insect some of which are popularly used across the country in households / farms / godowns.