Repellent activity of nanocrystalline ammonium paratungstate on the German cockroach, Blattella germanica (L.)

Abstract

Metal-based nanomaterials’ action as a repellent against the German cockroach, Blattella germanica (Blattodea: Ectobiidae), was examined. After the inner surfaces of black non-transparent rectangular plastic cases were sprayed with colloidal solutions of nanocrystalline ammonium paratungstate or pure water, two black cases were placed as shelters in a large container. Then adult cockroaches were introduced into the container. Cockroaches in shelters were counted 1–3 h later. When using boxes sprayed with 3.0 % colloidal solution and pure water, no cockroach that entered either of the shelters chose the shelter with nanocrystalline ammonium paratungstate. Even with concentrations lower than 3.0 %, fewer cockroaches chose shelters sprayed with the nanomaterial solution over those sprayed with pure water. The repellent effects persisted for 90 days and then decreased gradually. When cockroaches were reared in the container sprayed with the colloidal solution for a week, mortality was only 6 %, which was not different from that of the control experiment. Chemical insecticides in human dwellings pose a risk of human exposure. By contrast, a low impact on human health is expected from the non-volatile nanomaterial used for this study, which shows persistent repellency lasting for several months. Nanocrystalline ammonium paratungstate can be a strong tool when used as part of integrated pest management for cockroaches.