SMALL CHAMBER TESTS OF ETHYLENE DIBROMIDE AND ETHYLENE DICHLORIDE ON ADULT GRAIN-INFESTING COLEOPTERA

Abstract

Six strains of adult Silophilus granurius and one each of Tribolium confusum and Oryzaephilus surinamensis were fumigated with ethylene dibromide and ethylene dichloride to evaluate a small chamber fumigation technique as a means of establishing susceptibility levels. The influence of external factors, including the effect of insect diet before and after fumigation, on the comparative mortalities was also investigated. The suitability of this technique for detecting and comparing susceptibility differences was indicated.The LD50 values of a strain fumigated on different days varied as much as 40%, whereas the ratios of a standard and test strain fumigated on the same day varied less than 6% on different days.The natural mortality of S. granarius fed 10% sugar solution was less than that of those fed wheat grains. Sugar solution fed before exposure made the weevils more susceptible but when it was fed during the postexposure period it increased the observed LD50 by 60%.