Sublethal exposure enhances susceptibility to phosphine and affects certain fitness traits in red flour beetle Tribolium castaneum (Herbst)

The insecticidal gaseous phosphine would fail to meet the required concentration owing to improper sealing in a majority of bulk storage units. The resulting sublethal concentration has toxicological and biological implications for the target pests. The red flour beetle Tribolium castaneum has developed considerable resistance to phosphine. In this study, the effect of sublethal phosphine (LC₂₅ and LC₄₀) dose exposure is seen in the first filial generation of T. castaneum, where it was found to increase the susceptibility of the F₁ generation. The lethal concentration (LC₅₀) of parent stock (0.076 mg/ l) was reduced to 0.059 mg/ l and 0.052 mg/ l in the F₁ generation, respectively in the sample prior exposed to sublethal doses of LC₂₅ and LC₄₀. Surviving females of sublethal exposures (LC₄₀ and LC₂₅) produced fewer offspring with a cumulative fecundity reduction of 21 and 84% respectively, compared to parent stock. The variables tested in PCA highlight the negative effect of sublethal dose on the fecundity and fitness of female adults.