CYTOTOXIC EFFECT OF FENITROTHION AND ITS SYNERGIST PBO ON ALPHITOBIUS DIAPERINUS (COLEOPTERA: TENEBRIONIDAE) FOR BIOLOGICAL SECURITY OF STORED GRAINS AND CEREALS

To investigate the co-toxicity and co-efficient activity of Cypermethrin (Cythrin 20EC), a pyrethroid and Pyperonyl butoxide (PBO) against Alphitobius diaperinus (Panzer) (Coleoptera: Tenebrionidae). Repellency test was done by the residual film assay technique. Statistically the dose mortality relationship was expressed as a median lethal dose (LD 50 ) by the probit analysis. The regression lines and isoboles were drawn using the Fig-P (Biosoft) package. The Co-efficient values showed that all ratios of cypermethrin and piperonyl butoxide offered synergistic action to both larvae and adult. We observed that the toxicity of the cypermethrin was decreased as the ratio (amount) of PBO was increased. The individual LD 50 value of cypermethrin for adult is 0.1235µgcm -2 . But in the mixture, the share of cypermethrin are 0.0080, 0.0058, 0.0018 and 0.0015µgcm -2 at ratios of 1:1, 1:3, 1:5;1:10 when PBO causes reduction of dose level of 93.52%, 95.30%, 98.54% and 98.78% respectively. In case of larvae the individual LD 50 value of cypermethrin is 0.0476µgcm -2 . But in the mixture, the share of cypermethrin are 0.0055, 0.0046, 0.0022 and 0.0013µgcm 2 at ratios of 1:1, 1:3, 1:5;1:10 when PBO causes reduction of dose level of 76.89%, 61.34%, 72.26% and 69.74% respectively. The study suggests that the mortality rate of lesser meal worm is increase with the increase of insecticide dose. The LD 50 values of the insecticides are inversely related to the toxicity of the insecticides i.e. higher the LD 50 value lower the toxicity of the insecticide.