A way of action of the fenitrothion microcapsule as a residual cockroach control formulation

A way of action of the fenitrothion microcapsule as a residual spray formulation against cockroaches was studied. The microcapsule was prepared using polyurethane as a wall material (mass median diameter: 50μm, wall thickness: 0.14μm). The microcapsule was applied on a petri dish and the amount of fenitrothion outside the microcapsule was determined before and after cockroaches contacted with it. The results indicate that the spontaneous release of fenitrothion by diffusion through the capsule wall is not a main way of action, and that the microcapsule does not act as a stomach poison but as a contact poison. A main way of action of the microcapsule is trampling by cockroaches, which releases enough fenitrothion to kill tramplers.