Toxicity of Phosphine to Insect Pests and recent trends in Application Techniques

Phosphine scores over other fumigants on many
aspects including ease in application, low cost, less
residue problem and least effects on treated food
commodities. It is the major fumigant currently
used for the protection of stored' products in- India
and elsewhere. It has certain unique features in its
toxic action against insects. Large variations are
observed in the susceptibility not only between the
developmental stages of the same species but also
between the age groups of the same life stage.
Longer exposure period is essential for its effective
ness. Insects are narcotized at higher phosphine
concentrations. The toxicity is not enhanced by
combining with any other fumigant. Carbon
dioxide, although potentiates phosphine toxicity in
some species, the effect is not noticed in the
tolerant stages of other species. Sublethal doses of
phosphine induce the stored products insects to
develop resistance quickly. Recent advances in
phosphine dosing methods aiming at complete
control are also discussed.