The use of an aspirated sieve to remove insects, mites and pesticides from grain

A series of experiments examined the removal of insects, mites and insecticide residues from grain passed through a grain-cleaner comprising a de-awner and aspiration chamber and a sequence of inclined, reciprocating sieves. The cleaner was evaluated for its ability to remove adult insects from 1 kg grain samples by comparing the removal of 30 and 200 insects of each of Oryzaephilus surinamensis (L.), Sitophilus granarius (L.) and Cryptolestes ferrugineus (Stephens) using 1.0 and 2.0 mm sieves. Pest-free samples were reliably produced using a 2.0 mm sieve at the cost of a loss of about 4.5% in weight of dockage or cleanings removed. Cleaning produced a 90% reduction in live mite numbers but populations partially recovered afterwards, although still reaching only one-fifth of the uncleaned controls. After cleaning, 90% alive and dead Glycyphagus destructor were recovered from the cleanings but only 30% of Acarus siro were in the cleanings with a further 10% in the prime grain, leaving about 60% unaccounted for. Removal of about 1.6% dockage or cleanings resulted in a loss of approximately 20% of pesticide in half of the tests using etrimfos and pirimiphos-methyl emulsifiable concentrates and dust at 2 and 4 mg/kg.