Toxicity of Hydrogen Phosphide to The Granary Weevil, Sitophilus granarius, and Other Insects1

The order of toxicity of hydrogen phosphide to some stored-grain pests was determined and the response of Sitophilus granarius (L.) was studied in detail. With the exception of S. granarius adults, all insects exposed to hydrogen phosphide gave consistent responses in all experiments. With S. granarius, comparison of the weight of the survivors from treatment with that of normal insects, comparative tolerance of male and female adults of different ages, and variations of either of the components of the concentration × time product failed to account for the inconsistent responses of the adults to this fumigant. Hydrogen phosphide partially inhibited the oxygen uptake of S. granarius. A study of the effect of very short exposure times on the toxicity of the fumigant to S. granarius adults showed that maximum mortality for a given treatment was approached after only a few minutes of exposure.