Division of Entomology, Indian Agricultural Research Institute, New Delhi-110 012.
Ten insecticides comprising non-pyrethroids were evaluated against the adults of rust red flour beetle, Tribolium castenum (Herbst), by direct spray and film residue biosssay methods. Methyl parathion was the most toxic insecticide, irrespective of the method used. Fenitrothion and dimethoate were significantly more toxic as direct sprays than as film residues, while the toxicity of the rest of the insecticides was comparable when used either by direct spray or by film residue method. The resistance ratios in the case of malathion obtained by direct spray method were comparable with that obtained from film residue method i.e., 18.00 and 18.82, respectively. Therefore, instead of insecticide impregnated filter paper method recommended by FAO method No. 6, the direct spray method, which is easy to handle and less labour intensive, provided conditions similar to those prevailing in the field and is equally suitable. Obviously, the applicability of this method of assessment of resistance management seems to be more appropriate.
