The screening and sorting of many harvested crops is an effective method
of preventing infested produce from entering the food chain in developed
countries and in classifying produce according to suitability for animal or
human feed in developing countries. For example Compton and Sherington
(1999) describe a simple technique for classifying maize cobs into categories
based on the level of damage by visual comparison with standard pictures,
which is suitable for use by subsistence farmers. Screening and sorting
measures are designed to remove pests or prevent their access to the
product or commodity. Systems have been designed to separate out infested
grains by projection through air or by aspiration technology. In fl our
mills screens and sifters remove insect stages and fragments from the
production line.