Dry silica dust-based products for management of ixodids

Ixodids transmit a variety of disease-causing agents that afflict humans, livestock, companion animals, and wildlife, as well as reducing meat and milk yields, reproduction, hide quality, and occasionally inducing death from exsanguination. While the primary control tactic has been application of conventional synthetic acaricides, resistance to many of those products has occurred among various ixodid species. This development has instigated searches for alternative control tactics, such as growth regulators, bioactive animal and botanical substances, vaccines, biological control, and silica-based dusts. Inert silica dust-based substances, including kaolin, silica gel, diatomaceous earths, and perlite are lethal to mobile ixodid life stages. The dusts are largely noninjurious to vertebrates and they have potentially indefinite shelf lives and extended residual potential after application to vegetation and animals that host ixodids, e.g., cattle. Extended residual efficacy may confer prophylactic protection of livestock. Silica-based dusts, particularly diatomaceous earths, are acceptable for use in organically certified production systems and environmentally protected areas. Ixodid resistance is unlikely to occur, and ixodid vulnerability can be maintained by using silica-based dusts formulated with botanical toxins, such as pyrethrins and thyme oil. While silica-based dusts kill immature ixodids before they commence blood-feeding on cattle, the dusts combined with botanical toxins rapidly kill actively feeding ixodids as well. It is possible that commercially available silica-based dust products, and those formulated with botanical toxins, might be amenable to organic production systems and protected habitats.