The protection of bagged grain from insect infestation using fenitrothion

Abstract

Fenitrothion applied as an emulsion to wheat and barley of 11 and 12 per cent moisture content, respectively, or to the outside of sacks, was highly effective for the protection of bagged grain stored at 25°C, under conditions of heavy cross-infestation pressure by Oryzaephilus surinamensis, Sitophilus granarius and Tribolium castaneum. O. surinamensis was the most susceptible and T. castaneum the most tolerant of the insects used. For admixture, dosages of 2 ppm gave satisfactory protection for 6 months and 4 ppm for 10 months. For the external treatment of sacks, a single treatment of 80–160 mg fenitrothion/ft 2 (860–1720 mg/m 2) gave good protection for at least 6 months. O. surinamensis was the least susceptible insect to this form of control, probably because its small size permits quick penetration of the sacking. There was a gradual degradation of fenitrothion with time but in grain the effectiveness of a given dose is dependent on a combination of concentration and time after treatment.